Agriculture Terminology

Understanding stewardship through key terms and definitions

Stewardship is an essential, joint effort between farmers, pesticide applicators, consultants, and others. Learn important terms to help you understand stewardship as a crucial component of pesticide use, as well as terms regarding agricultural practices, pesticides, and government regulations.

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Absorbed Dose - In exposure assessment, the amount of a substance that penetrates an exposed organism's absorption barriers (e.g., skin, lung tissue, gastrointestinal tract wall, etc.) through physical or biological processes. The term is synonymous with internal dose.

Absorption - The movement of a chemical into plants, animals (including humans), microorganisms, or soil.

Absorption Barrier - Any of the exchange sites of the body through which uptake of various substances at different rates (e.g., skin, lung tissue, gastrointestinal tract wall) occurs.

Acceptable Daily Intake (ADI) - The amount of a chemical a person can be exposed to on a daily basis over an extended period of time (usually a lifetime) without suffering negative effects. See Reference Dose.

Acid Equivalent (ae) - For those pesticides that are acids, acid equivalent is the amount of active ingredient expressed in terms of the parent acid.

Action Levels - (1) Regulatory levels recommended by EPA for enforcement by FDA and USDA when pesticide residues occur in food or feed commodities for reasons other than the direct application of the pesticide. As opposed to "tolerances" which are established for residues occurring as a direct result of proper usage, action levels are set for inadvertent residues resulting from previous legal use or accidental contamination. (2) In the Superfund program, the existence of a contaminant concentration in the environment high enough to warrant action or to trigger a response under SARA and the National Oil and Hazardous Substances Contingency Plan. The term is also used in other regulatory programs.

Activated Carbon/Activated Charcoal - A highly adsorbent form of carbon used to remove odors and toxic substances from liquid or gaseous emissions. In waste treatment, it is used to remove dissolved organic matter from waste drinking water.

Activator - An adjuvant added to a pesticide to increase its toxicity.

Active Ingredient (ai) - The chemical or chemicals in a product responsible for pesticidal activity.

Acute Effects - Illnesses or injuries that occur shortly (within 24 hours) after exposure to a pesticide.

Acute Exposure - Exposure to a chemical for a short period of time.

Acute Toxicity - Adverse effects that result from a single dose or single exposure of a chemical; any poisonous effect produced within a short period of time, usually less than 96 hours. This term normally is used to describe effects in experimental animals.

Adjuvant - A substance that improves the properties of a pesticide formulation, e.g., wetting agents, spreaders, emulsifiers, dispersing agents, foam suppressants, penetrants, and correctives.

Adsorption - The process whereby chemicals are held or bound to a surface by physical or chemical attraction. Clay and high-organic soils tend to adsorb pesticides.

Adulterated - (1) Any pesticide whose strength or purity falls below the quality stated on its label. (2) A food, feed, or product that contains illegal pesticide residues.

Adverse Effect - Change in the morphology, physiology, growth, development, reproduction or life span of an organism, system, or subpopulation that results in impairment of the capacity to compensate for additional stress, or an increase in susceptibility to other influences.

Adverse Effect Data - FIFRA requires a pesticide registrant to submit data to EPA on any studies or other information regarding unreasonable adverse effects of a pesticide at any time after its registration.

Aerated Lagoon - A holding and/or treatment pond that speeds up the natural process of biological decomposition of organic waste by stimulating the growth and activity of bacteria that degrade organic waste.

Agricultural Pollution - Farming wastes, including runoff and leaching of pesticides and fertilizers; erosion and dust from plowing; and improper disposal of animal manure and carcasses, crop residues, and debris.

Air Pollutants - Any substance in air that could, in high enough concentration, harm man, other animals, vegetation, or material. Pollutants may include almost any natural or artificial composition of airborne matter capable of being airborne. They may be in the form of solid particles, liquid droplets, gases, or in combination thereof. Generally, they fall into two main groups: (1) those emitted directly from identifiable sources and (2) those produced in the air by interaction between two or more primary pollutants, or by reaction with normal atmospheric constituents, with or without photoactivation. Exclusive of pollen, fog, and dust, which are of natural origin, about 100 contaminants have been identified. Air pollutants are often grouped in categories for ease in classification; some of the categories are: solids, sulfur compounds, volatile organic chemicals, particulate matter, nitrogen compounds, oxygen compounds, halogen compounds, radioactive compound, and odors.

Alkaline - Basic, having a pH greater than 7. Some pesticides are adversely affected in alkaline spray solutions or carry over (persist in soil so that injury may occur in a subsequent crop) longer in high pH soils.

Allelopathy - The adverse effect on the growth of plants or microorganisms caused by the action of chemicals produced by other living or decaying plants.

Allergic Effects - A hypersensitivity to a specific substance, often called the allergen. An allergy may cause dermatitis, blisters, or hives. It could also cause illness, asthma, or life-threatening shock. Often the entire body is affected. Pesticide allergy symptoms are similar to other allergy symptoms—reddening and itching of the eyes, respiratory discomfort, and asthma-like symptoms.

Annual - A plant that completes its life cycle in one growing season or a single year. The seed germinates and the plant grows, blooms, fruits/sets seed, and dies all in one growing season. The phrase “grow as an annual” or “treat as an annual” refers to technically perennial plants that are most attractive only during their first year and, hence, are better grown as new plants each year. See Summer Annual and Winter Annual.

Antidote - Substance used as a medical treatment to counteract pesticide poisoning.

Anti-Siphoning Device - A hose attachment designed to prevent backflow of a pesticide mix from the spray tank into a water source.

Aquifer - A sand, gravel or rock formation capable of storing or conveying water; an underground geological formation or group of formations containing usable amounts of groundwater that can supply wells or springs.

Aquifer, Confined - Soil or rock below the land surface that is saturated with water. There are layers of impermeable material both above and below it and it is under pressure so that when the aquifer is penetrated by a well the water will rise over the top of the aquifer.

Aquifer, Unconfined - An aquifer containing water that is not under pressure; the water level in the associated well is the same as the water table outside the well. Conversely, confined aquifers are under pressure.

Available Nutrients - Minerals or chemicals in forms that plants can absorb and utilize for growth.


Backflow - The reversal of water flow from its normal or intended direction of flow.

Back-Siphoning - Occurs when there is a partial vacuum (negative pressure) in a water supply system, which draws the water from a contaminated source into a potable water supply.

Bacteria - Single-celled microorganisms that lack chlorophyll. Some bacteria are capable of causing human, animal or plant diseases; others are essential in pollution control because they break down organic matter in the air and water.

Bed - (1) A ridge of soil for planting crops above furrows on each side. (2) An area in which seedlings or transplants are grown for planting in the field later.

Best Management Practices (BMPs) - Procedures or controls other than effluent limitations to prevent or reduce pollution of surface water (includes runoff control, spill prevention, and operating procedures). See Syngenta and Water.

Biennial - A plant that completes its life cycle in two years. Typically, seeds germinate and plants grow plants grow vegetatively during the first year, forming a rosette. In the second year of growth, biennials send up a flowering stalk. After flowering and seed production, biennials die. Biennials can have large taproots, which sometimes causes people to confuse them with perennials.

Bioaccumulation - An increase in the concentration of a chemical in a biological organism over time, compared to the chemical's concentration in the environment. Compounds accumulate in living things any time they are taken up and stored faster than they are broken down (metabolized) or excreted. Understanding the dynamic process of bioaccumulation is very important in protecting human beings and other organisms from the adverse effects of chemical exposure, and it has become a critical consideration in the regulation of chemicals. See also Bioconcentration and Biomagnification.

Bioassay - A laboratory test which determines the strength or biological effects of a substance, such as a drug, hormone or chemical; the test is done by comparing the experimental substance's effects with those of a known substance on a culture of living cells or a test organism.

Bioavailability - How easily a plant or animal can take up a particular substance from the environment.

Bioconcentration - The specific bioaccumulation process by which the concentration of a chemical in an organism becomes higher than its concentration in the air or water around the organism. Although the process is the same for both natural and manmade chemicals, the term bioconcentration usually refers to chemicals foreign to the organism. For fish and other aquatic animals, bioconcentration after uptake through the gills (or sometimes the skin) is usually the most important bioaccumulation process.

Biodegradable - Capable of decomposing under natural conditions.

Biodegradation - The breaking down of a chemical by organisms in the environment.

Biodiversity - Refers to the variety and variability among living organisms and the ecological complexes in which they occur. Diversity can be defined as the number of different items and their relative frequencies. For biological diversity, these items are organized at many levels, ranging from complete ecosystems to the biochemical structures that are the molecular basis of heredity. Thus, the term encompasses different ecosystems, species, and genes.

Biological Control/Biocontrol -Pest management using predators, parasites, or pathogens. It may be naturally occurring or introduced.

Biological/Biochemical Oxygen Demand (BOD) - An indirect measure of the concentration of biologically degradable material present in organic wastes. It usually reflects the amount of oxygen consumed in five days by biological processes breaking down organic waste.

Biomagnification - Describes a process that results in the accumulation of a chemical in an organism at higher levels than are found in its food. It occurs when a chemical becomes more and more concentrated as it moves up through a food chain (the dietary linkages between single-celled plants and increasingly larger animal species). A typical food chain includes algae eaten by the water flea eaten by a minnow eaten by a trout and finally consumed by an osprey (or human being). If each step results in increased bioaccumulation, that is, biomagnification, then an animal at the top of the food chain, through its regular diet, may accumulate a much greater concentration of chemical than was present in organisms lower in the food chain. This is illustrated by a study of DDT which showed that, where soil levels were 10 parts per million (ppm), DDT reached a concentration of 141 ppm in earthworms and 444 ppm in robins. Through biomagnification, the concentration of a chemical in the animal at the top of the food chain may be high enough to cause death or adverse effects on behavior, reproduction, or disease resistance and thus endanger that species, even when levels in the water, air, or soil are low. Fortunately, bioaccumulation does not always result in biomagnification.

Bioremediation - (1) Process of using the enzymatic actions of microbes to degrade contaminants. (2) Process of transforming pesticide waste to less toxic products using microbial activity. (3) Use of plants to remove pollutants from soil or water by root or foliar uptake followed by removal and disposal of the plant.

Biotechnology - Techniques that use living organisms or parts of organisms to produce a variety of products (from medicines to industrial enzymes) to improve plants or animals or to develop microorganisms to remove toxins from bodies of water, or to act as pesticides.

Bloom - A proliferation of algae and/or higher aquatic plants in a body of water; often related to pollution or excessive nutrients, especially when they accelerate growth, but can also be a natural part of a life cycle.

Breakdown - See Degradation.

Breakthrough - The penetration of pesticide through PPE, such as a liquid through gloves or a gas through a respirator. If this happens, the PPE is no longer protective.

Broadleaf - Plant with broad, rounded, or flattened leaves with netted veins.

Buffers - Adjuvants used to slow chemical degradation of some pesticides by lowering the pH of alkaline water and maintaining the pH within a narrow range, even with the addition of acidic or alkaline materials.

Buffer Strip - Narrow area of permanent vegetation often planted at the edge of a field, typically to slow the flow of water, slow the velocity of the wind, or to filter sediment and chemicals from runoff. Placed around fields, they can enhance wildlife habitat, improve water quality, and enrich aesthetics on farmlands. Various types of buffers include contour buffer strips, filter strips, riparian buffers, field borders, windbreaks/shelterbelts, hedgerows, grassed waterways, and alley cropping.


Carcinogen - A substance or agent capable of causing cancer.

Carrier - (1) An inert liquid, solid, or gas added to an active ingredient to make a pesticide formulation. (2) The material, usually water or oil, used to dilute the formulated product for application.

Carryover - Persistence of pesticide residues in soil after use in one crop, such that injury may occur in a subsequent more sensitive crop. Carryover potential is higher in soils high in clay, organic matter, cation exchange capacity, and pH and lower in soils high in microbial and chemical activity. Certain pesticide characteristics increase potential for carryover. Carryover potential can be reduced by uniformly applying the lowest recommended rate, accurately determining acreage and measuring chemical, and properly calibrating sprayer. Banding of pesticides, early-season application, tillage and cultivation, tank mixtures to reduce the rate of the persistent partner, and selection of a tolerant rotational crop or variety help minimize carryover problems.

Certified Applicator - A person qualified to apply or supervise the application of restricted-use pesticides.

Chemical Degradation - The breakdown of pesticides by a chemical process, usually by a chemical reaction with water (hydrolysis) or with UV light (photolysis).

Chemical Fallow (Eco-fallow) - A special kind of fallowing in which all vegetative growth is killed or prevented by use of chemicals; tillage for other purposes may or may not be used.

Chemical Name - The technical term for the active ingredient(s) found in the formulated product. This complex name is derived from the chemical structure of the active ingredient.

Chemical-Resistant - In reference to personal protective equipment, a material that allows no measurable movement of the pesticide being used through it during use.

Chemigation - The application of pesticides or fertilizers to a target site in irrigation water. Also known as injector systems when used in greenhouses.

CHEMNET® - A network of for-hire contractors (primarily in the U.S.) for CHEMTREC registrants who may need the services of an emergency response contractor at the scene of an incident involving a registrant’s product.

CHEMTREC® - The Chemical Transportation Emergency Center. It supports a toll-free number (800-424-9300) that provides 24-hour information for chemical emergencies, such as a spill, leak, fire, or accident.

Child Hazard Warning - The “Keep out of Reach of Children” (KOOROC) statement which appears on almost all end-use pesticide products except those pesticides that are intended for use on children or where it is demonstrated that children will not come in contact with the product.

Chlorosis - Yellowing or bleaching of normally green plant tissue usually caused by the loss of chlorophyll.

Chronic Exposure - Multiple exposures occurring over an extended period of time or over a significant fraction of an animal's or human's lifetime (usually seven years to a lifetime).

Chronic Toxicity - (1) The ability of small amounts of pesticide from repeated, prolonged exposure to cause injury. (2) Effects that persist over a long period of time whether or not they occur immediately upon exposure or are delayed.

Code of Federal Regulations (CFR) - Document that codifies all rules of the executive departments and agencies of the federal government. It is divided into fifty volumes, known as titles. Title 40 of the CFR (referenced as 40 CFR) lists all environmental regulations.

Commercial Applicator - A certified applicator who uses or supervises the use of pesticides for purposes other than those covered under a private applicator certification.

Common Name - (1) A name given to a pesticide active ingredient by a recognized committee on pesticide nomenclature. Although many pesticides are known by a number of trade or brand names, each active ingredient has only one recognized common name, e.g., propiconazole is the common name for 1-((2-(2,4-Dichlorphenyl)-4-propyl-1,3-dioxolan-2-yl)methyl)-1H-1,2,4-triazole. (2) A non-Latin name for a plant species.

Community Water System (CWS) - A public water system which serves at least 15 service connections used by year-round residents, or regularly serves at least 25 year-round residents.

Companion Crop/Nurse Crop - One crop sown with another, used particularly of the small grains with which forage crops are sown. “Companion crop” is the preferred term.

Compatibility Agent - An adjuvant used to enhance the mixing of two or more pesticide products and/or fertilizers.

Compatible - When two or more chemicals are mixed without reducing the effectiveness or characteristics of any individual chemical.

Composting - The controlled biological decomposition of organic material in the presence of air to form a humus-like material. Controlled methods of composting include mechanical mixing and aerating, ventilating the materials by dropping them through a vertical series of aerated chambers, or placing the compost in piles out in the open air and mixing it or turning it periodically.

Concentrate - A pesticide formulation before it is diluted. Compare to Dilute .

Concentrated Flow - A relatively large water flow over or through a relatively narrow course.

Concentration - The amount of active ingredient in a given volume or weight of formulated product.

Confidential Business Information (CBI) - Material that contains trade secrets or commercial or financial information that has been claimed as confidential by its source (e.g., a pesticide or new chemical formulation registrant). EPA has special procedures for handling such information.

Confidential Statement of Formula (CSF) - A list of the ingredients in a new pesticide or chemical formulation. The list is submitted by the registrant at the time for application for registration or change in formulation.

Conservation - The use, protection, renewal, and improvement of natural resources according to principles that will ensure their highest economic or social benefits.

Conservation Buffers - Strips or other areas with trees or grass that help control pollutants, erosion, or other environmental concerns.

Conservation Easement - Easement restricting a landowner to land uses that are compatible with long-term conservation and environmental values.

Conservation Reserve Program (CRP) - A federal program under which producers voluntarily retire environmentally sensitive crop land for 10 to 15 years in return for annual rental payments through which the government shares the cost of establishing approved conservation practices. Payments are through the USDA Commodity Credit Corporation.

Conservation Tillage - (1) Any of several farming methods that provide for seed germination, plant growth, and weed control yet maintain effective ground cover throughout the year and disturb the soil as little as possible. The aim is to reduce soil loss and energy use while maintaining crop yields and quality. No-till is the most restrictive (soil-conserving) form of conservation tillage. (2) Any tillage and planting system that covers 30 percent or more of the soil surface with crop residue, after planting, to reduce soil erosion by water. Where soil erosion by wind is the primary concern, any system that maintains at least 1,000 pounds per acre of flat, small grain residue equivalent on the surface throughout the critical wind erosion period. Reduced till is not necessarily a type of conservaion tillage, but it could be.

  • No Till (Zero Till) - A procedure whereby a crop is planted directly into the soil with no primary or secondary tillage since harvest of the previous crop; usually a special planter is necessary to prepare a narrow, shallow seedbed immediately surrounding the seed being planted. Weed control is accomplished primarily with crop protection products.
  • Strip Till - Tillage operations performed in isolated bands separated by bands of soil essentially undisturbed by the particular tillage equipment.
  • Mulch Till - Tillage or preparation of the soil in such a way that plant residues or other materials are left to cover the surface; also, mulch farming, trash farming, stubble mulch tillage, plowless farming; operationally, a full-width tillage or tillage and planting combination that leaves > 30% of the surface covered with crop residue. Tillage tools such as chisels, field cultivators, disks, sweeps, or blades are used.
  • Ridge Till - The soil is left undisturbed from harvest to planting except for strips up to 1/3 of the row width. Planting is completed on the ridge and usually involves the removal of the top of the ridge. Planting is completed with sweeps, disk openers, coulters, or row cleaners. Residue is left on the surface between ridges. Weed control is accomplished with crop protection products (frequently banded) and/or cultivation. Ridges are rebuilt during row cultivation.
  • Zone Till - Sometimes called vertical tillage. Must leave >30% residue to be considered conservation tillage

Containment Pad - An impermeable mat used for mixing and loading pesticides and cleaning equipment that is designed to catch spills, leaks, overflows, and wash water for reuse or disposal.

Contour Buffer Strips - Permanent, narrow bands of grasses/legumes planted on the contour (across or perpendicular to a slope) between wider strips of crops farmed on the contour. They are designed to reduce soil erosion and runoff on sloped fields. To serve this purpose, contour buffer strips must stay in the same location where originally established, i.e., they cannot rotate as part of a crop rotation.

Contour Farming - Field operations such as plowing, planting, cultivating, and harvesting on the contour, or at right angles to the natural slope, to reduce soil erosion, protect soil fertility, and use water more efficiently.

Contour Strip-Cropping - Crop rotation and contouring combined in equal-width strips of row crop (typically corn or soybeans) planted on the contour and alternated in a planned rotation with equal-width strips of close-growing crops such as forages, small grains, or sod, all arranged systematically across a field and down a slope on the contour to reduce soil erosion and run-off. Rotating the crops from corn to legumes allows nutrient-needy crops to benefit from the nitrogen added to the soil by legumes.

Conventional Reduced-Risk Pesticide Program - Program that expedites the review and regulatory decision-making process of conventional pesticides that pose less risk to human health and the environment than existing conventional alternatives. The goal of this program is to quickly register commercially viable alternatives to riskier conventional pesticides such as neurotoxins, carcinogens, reproductive and developmental toxicants, and groundwater contaminants. Participants in the program include the chemical companies and state or federal agencies that submit to the Agency initial registration and amended registration applications for pesticide products. While most reduced risk discussions refer to conventional reduced risk pesticides, a reduced risk decision is actually made at the use level, for a pesticide/use combination.

Cover Crop - A crop grown between periods of regular production of the main crop for the purposes of protecting the soil from erosion and improving soil productivity, health, and quality.

Critical Area Planting - Establishing permanent vegetation on sites that have, or are expected to have, high erosion rates, and on sites that have physical, chemical or biological conditions that prevent the establishment of vegetation with normal practices.

Crop Residue Management (CRM) - A year-round system beginning with the selection of crops that produce sufficient quantities of residue and may include the use of cover crops after low-residue-producing crops. CRM includes all field operations that affect residue amounts, orientation and distribution throughout the period requiring protection. Site-specific residue cover amounts needed are usually expressed in percentage but may also be in pounds. CRM is an “umbrella” term encompassing several tillage systems including no-till, ridge-till, mulch-till, and reduced-till.

Crop Rotation - System of cultivation where different crops are planted in consecutive growing seasons to maintain soil fertility.

Crop Scouting - A regular and systematic field-sampling program that provides field-specific information on pest pressure and crop injury that is essential to the appropriate selection and application of pest management procedures and an essential part of Integrated Pest Management.

Cross-resistance - When a pest population that is already resistant to one pesticide becomes resistant to a related chemical with a similar mode of action.

Cultivation - Shallow tillage operations performed to create soil conditions conducive to improved aeration, infiltration, and water conservation, or to control weeds. See Tillage.

Cultural Weed Control - The establishment of competitive and desired vegetation to prevent or slow down invasion by weedy species is a key component of successful weed management. Success often depends on proper species selection suitable for a particular soil type, moisture regime, and growing season.

Cumulative Risk - Probability of any defined harmful effect occurring through a common toxic effect associated with concurrent exposure by all relevant pathways and routes of exposure to a group of chemicals that share a common mechanism of toxicity.


Data Call-In - A part of the Office of Pesticide Programs (OPP) process of developing key required test data, especially on the long-term, chronic effects of existing pesticides, in advance of scheduled Registration Standard reviews. Data Call-In from manufacturers is an adjunct of the Registration Standards program intended to expedite re-registration.

Data Compensation - Under U.S. law, companies who are the original submitters of data to support product registrations are entitled to receive financial compensation for the data when their competitors rely on such data to obtain their own or substantially similar pesticide registrations (e.g., generic or “me-too” registrations). For a new active ingredient, FIFRA 3(c)(1)(F) entitles the original data submitter to 10 years exclusive use protection plus 5 years of data compensation. For all other eligible data, 15 years of data compensation is allowed from the date of the submission.

Decontaminate - To remove or degrade a chemical residue from the skin or a surface.

Degradation - The process by which a chemical compound is broken down into simpler compounds by the action of microorganisms, water, air, sunlight, or other agents. Degradation products are usually — but not always — less toxic than the original compound. See Chemical Degradation, Hydrolysis, Microbial Degradation, and Photodegradation.

Delayed Effects - Illnesses or injuries that do not appear immediately (within 24 hours) after exposure to a pesticide. The effects may be delayed for weeks, months, or even years.

Dermal Exposure - Contact between a chemical and the skin.

Dermal Toxicity - Ability of a pesticide or other chemical to poison people or animals by contact with the skin.

Dermatitis - The inflammation, itching, irritation, or occurrence of a rash after exposure to a chemical or an irritant such as poison ivy or poison oak.

Detection Limit - The lowest concentration of a chemical that can reliably be distinguished from a zero concentration.

Detention Time - The time required for a volume of water to pass through a tank at a given rate of flow; in storage reservoirs, the length of time water will be held before being used.

Development Effects - Adverse effects such as altered growth, structural abnormality, functional deficiency, or death observed in a developing organism.

Diluent - Any liquid or solid material serving to dilute or carry an active ingredient. Diluents may aid in mechanical application of a formulated pesticide, but do not directly influence their toxicity (e.g. water in sprays, oils in sprays, finely-ground inert materials in dust).

Dilute - Made less concentrated by the addition of a liquid such as water. Also see Concentrate.

Direct Filtration - A filtration method of treating water which consists of the addition of coagulant chemicals, flash mixing, coagulation, minimal flocculation, and filtration. The flocculation facilities may be omitted, but the physical-chemical reactions will occur to some extent. The sedimentation process is omitted.

Disease Cycle - In a disease caused by a biotic agent, the cyclical sequence of host and pathogen development and interaction that result in disease, in reproduction or replication of the pathogen, and in the readying of a new generation of the pathogen for infection.

Disk - A type of cultivator made up of many circular blades used for weed control and soil preparation.

Dispersing Agent - An adjuvant that facilitates the mixing and suspension of a pesticide formulation in water.

Disposal - Final placement or destruction of toxic, radioactive, or other wastes; surplus or banned pesticides or other chemicals; polluted soils; and drums containing hazardous materials from removal actions or accidental releases. Disposal may be accomplished through means such as use of approved secure landfills, surface impoundments, land farming, deep-well injection, ocean dumping, or incineration.

Dissipation - Loss of pesticide residues from an environmental compartment due to degradation and transfer to another environmental compartment.

Dissolved Oxygen (DO) - Amount of oxygen gas dissolved in a given quantity of water at a given temperature and atmospheric pressure. It is usually expressed as a concentration in parts per million or as a percentage of saturation.

Dissolved Solids - Inorganic material contained in water or wastes. Excessive dissolved solids make water unsuitable for drinking or industrial uses.

Distributor - A company which sells a registrant’s product under their own name and address under a supplemental distribution agreement. The distributor, also known as a sub-registrant, is considered an agent of the registrant, and both the registrant and the distributor may be held liable for violations pertaining to the distributor product.

Diversion - A channel to slow, divert or collect water and/or reduce runoff. Diversions may be used to protect bottomland from hillside runoff, divert water away from active gullies, or protect buildings from runoff.

Dormancy - State of inhibited seed germination or growth of a plant organ when in an environment normally conducive to growth.

Dose-Response Relationship - Relationship between the amount of a pesticide (or agent) administered to, taken up or absorbed by an organism, system, or (sub-) population and the change developed in that organism, system, or (sub-) population in reaction to the pesticide (or agent).

Double-Cropping - Growing two crops subsequently on the same piece of land during a single year. For example, winter wheat may be harvested and immediately followed by a short-season soybean variety.

Drag - To draw planks or other heavy, rigid implements with wide surfaces across the soil surface to crush clods and level or smooth the surface.

Drag-Off - Cultivation (by harrowing) of the hill before the crop (especially potatoes) emerges. Herbicides may be applied after drag-off for control of un-emerged weeds.

Drift - The airborne movement of a pesticide spray, dust, particle, or vapor beyond the target area.

Drift Control Agent/Additive - An adjuvant added to a spray mixture to reduce drift.

Drinking Water State Revolving Fund (DWSRF) - The Fund provides capitalization grants to states to develop drinking water revolving loan funds to help finance system infrastructure improvements, assure source-water protection, enhance operation and management of drinking-water systems, and otherwise promote local water-system compliance and protection of public health.


EC50 - Median effective concentration. Statistically derived concentration of a pesticide in an environmental medium expected to produce a certain effect in 50 % of the test organisms in a given population under defined conditions.

Ecological Risk Assessment - A process in which EPA evaluates the likelihood that exposure to one or more pesticides may cause harmful ecological effects. The effects can be direct (e.g., fish die from a pesticide entering waterways, or birds do not reproduce normally after ingesting contaminated fish), or indirect (a hawk becomes sick from eating a mouse dying from pesticide poisoning). The likelihood of harmful effects is based on scientific measurements and scientific judgment.

Economic Threshold - A level of pest population or damage at which the cost of control action equals the crop value gained from control action.

Ecosystem - Assembly of populations of different species (often interdependent on and interacting with each other) together with non-living components of their environment.

Emergence - The event in seedling establishment when a shoot becomes visible by pushing through the soil surface.

Emergency Exemptions - Under Section 18 of FIFRA, EPA can allow state and federal agencies to permit the unregistered use of a pesticide in a specific geographic area for a limited time if emergency pest conditions exist. Usually this arises when growers and others encounter a pest problem on a site for which there is either no registered pesticide available or there is a registered pesticide that would be effective but is not yet approved for use on that particular site. Exemptions can also be approved for public health and quarantine reasons. Due to their nature, they include expiration dates.

Emulsifier - A chemical that aids in the suspension of one liquid in another that normally would not mix together.

Emulsion - A mixture of two liquids that are not soluble in each other. One is suspended as very small droplets in the other with the aid of an emulsifier. An example is emulsifiable concentrate in water.

Endangered Species - Animals, birds, fish, plants, or other living organisms threatened with extinction by man-made or natural changes in their environment. In the United States, the requirements are contained in the Endangered Species Act.

End-use Product - A pesticide formulation for field or other end use. The label has instructions for use or application to control pests or regulate plant growth. The term excludes products used to formulate other pesticide products.

Enhanced Degradation - Increased rate of degradation of a pesticide in soil or other environmental matrix by a population of microorganisms that has adapted to metabolize it through previous exposure to it or a similar chemical.

Enrichment - The addition of nutrients such as nitrogen and phosphorous from wastewater effluent or agricultural runoff to surface water. Enrichment greatly increases the growth potential for algae and other aquatic plants.

Environment - The sum of all external conditions affecting the life, development, and survival of an organism.

Environmental Fate - The interaction of pesticides with soils, air, sunlight, surface water, and ground water. Studies are used to answer basic questions like: (1) How fast and by what means does a pesticide degrade? (2) What are the breakdown chemicals? (3) How much of the pesticide or its breakdown chemicals will travel from the application site? Do they accumulate in the environment? If so, where?

Environmental Protection Agency (EPA) - The federal agency responsible for implementing pesticide rules and regulations and registering pesticides.

Eradication - A pest management strategy that attempts to eliminate all members of a pest population from a defined area, often attempted with invasive pests, e.g., the Mediterranean fruit fly.

Erodibility - (1) The degree or intensity of a soil's state or condition of, or susceptibility to, being erodible. (2) The K factor in the Universal Soil Loss Equation.

Erosion - The wearing away of the land surface by wind, water, ice or other geologic agents. Erosion occurs naturally from weather or runoff but is often intensified by human land use practices.

Eutrophication - Degradation of water quality due to enrichment by nutrients, primarily nitrogen (N) and phosphorous (P), which results in excessive plant (principally algae) growth and decay. When levels of N: P are about 7:1, algae will thrive. Low dissolved oxygen (DO) in the water is a common consequence.

Eutrophic Lakes - Biologic productivity is high and the nutrient load is also high. Lack of dissolved oxygen may occur in the deeper parts of a eutrophic lake because of thermal stratification. When lake temperatures are homogenous or the surface water is colder than the deep water, mixing occurs. If the deep water is colder than the surface water, no mixing will occur and the deeper water is essentially isolated from the oxygen and nutrients of the surface. This stratification is normally seasonal and occurs during the summer months. The evolution of natural lakes is normally from oligotrophic to eutrophic. An increase in sediment delivery to lakes can accelerate the eutrophication process because of nutrients that bind to fine sediments. Continued filling with sediments leads to advanced eutrophication, swampy or marshy conditions, and finally total infilling of the prior lake environment. See Oligotrophic Lakes and Mesotrophic Lakes.

Exemption - State or EPA permission for a water system not to meet a certain drinking water standard. An exemption allows a system additional time to obtain financial assistance or make improvements in order to come into compliance with the standard. The system must prove that: (1) there are compelling reasons (including economic factors) why it cannot meet a Maximum Contaminant Level (MCL) or Treatment Technique; (2) it was in operation on the effective date of the requirement, and (3) the exemption will not create an unreasonable risk to public health. The state must set a schedule under which the water system will comply with the standard for which it received an exemption. See Variance.

Experimental Use Permit (EUP) - Under Section 5 of FIFRA, EPA can allow manufacturers to field-test pesticides under development. Manufacturers of conventional pesticides must obtain experimental use permits before testing new pesticides or new uses of pesticides if they conduct experimental field tests on ten acres or more of land or one acre or more of water. Biopesticides also require EUPs when used in experimental settings.

Exposure - (1) How a biological system (i.e., ecosystem), plant, or animal comes in contact with a chemical. (2) Concentration or amount of a pesticide (or agent) that reaches a target organism, system, or (sub-) population in a specific frequency for a defined duration. (3) Unwanted contact with pesticides or pesticide residues by people, other organisms, or the environment.

Eyewash Dispenser - Commercially available system for flushing contaminants out of the eyes.


Fallow - The practice of leaving land uncropped and weed-free or with volunteer vegetation during at least one period when a crop would normally be grown; the objective may be to control weeds or to accumulate water and/or available plant nutrients.

Farm Pond - A pool of water formed by a dam or pit, to supply water for livestock, recreation and wildlife, and to control gully erosion. A typical farm pond is formed by building a dam across an existing gully or low lying area. Earth for the dam is dug out above the dam with heavy machinery to form a bowl. Generally the ponded area fills with water within a year. An overflow pipe is installed through the dam to control the water level and allow water to spill through the dam without causing erosion.

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) - The Federal Insecticide, Fungicide, and Rodenticide Act was enacted in June 25, 1947. The Act instructs the EPA to regulate: 1) the registration of all pesticides used in the United States, 2) the licensing of pesticide applicators, 3) re-registration of all pesticide products, 4) the storage, transportation, disposal and recall of all pesticide products. FIFRA's home page ( provides many more details.

Federal Register - The official daily publication for rules, proposed rules, and notices of federal agencies and organizations, as well as executive orders and other presidential documents. Access the FR online (

Filter Strip - Strip or area of vegetation used for removing sediment, organic matter, and other pollutants from runoff and wastewater.

Finished Water - Water that has passed through a water treatment plant; all the treatment processes are completed or "finished." This water is ready to be delivered to consumers.

Food Quality Protection Act (FQPA) - 1996 update/amendment to the U.S. Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) and the Federal Food Drug and Cosmetic Act (FFDCA). FQPA fundamentally changes the way EPA regulates pesticides to “establish a more consistent, protective regulatory scheme, grounded in sound science”. FQPA mandates a single, health-based standard for all pesticides in all foods; provides special protections for infants and children; expedites approval of safer pesticides; creates incentives for the development and maintenance of effective pesticides; and requires periodic re-evaluation of pesticide registrations and tolerances to ensure that the scientific data supporting pesticide registrations will remain up to date in the future. Also see Risk Cup.

Formulation - (1) A pesticide product as purchased, containing a mixture of one or more active ingredients, carriers (inert ingredients), and other additives diluted for safety and ease of application. (2) Process, carried out by manufacturers, of preparing pesticides for practical use.

Fungus - A multicellular lower plant lacking chlorophyll, such as mold, mildew, smut, or rust. The fungus body normally consists of filamentous strands called mycelium and reproduces through dispersal of spores.

Furrow - (1) An opening left in the soil after a plow or disk has opened a shallow channel at the soil surface. (2) A shallow channel cut in the soil surface, usually between planted rows, for controlling surface water and soil loss, or for conveying irrigation water.


Generally Recognized as Safe (GRAS) - Designation by the FDA that a chemical or substance (including certain pesticides) added to food is considered safe by experts, and so is exempted from the usual food additive tolerance requirements.

Genetic Engineering - The process of using recombinant DNA (rDNA) technology to alter the genetic makeup of an organism. Traditionally, humans have manipulated genomes indirectly by controlling breeding and selecting offspring with desired traits. Genetic engineering involves the direct manipulation of one or more genes. Most often, a gene from another species is added to an organism's genome to give it a desired phenotype, e.g., golden rice was developed by transforming rice with two beta-carotene biosynthesis genes from daffodil and a soil bacterium.

Germination - The sprouting of a seed or the production of a germ tube (mycelium) from a fungus spore.

Good Agricultural Practice (GAP) / Directions for Use (DFUs) - The officially recommended or nationally authorized uses of pesticides under actual conditions necessary for effective and reliable pest control. It encompasses a range of levels of pesticide applications up to the highest authorized use applied in a manner which leaves a residue that is the smallest amount practicable.

Grade Control Structure - A dam, embankment or other structure built across a grassed waterway or existing gully to control and reduce water flow. The structure drops water from one stabilized grade to another and prevents overfull gullies from advancing up a slope.

Grassed Waterway - Natural or constructed watercourse or outlet that is shaped or graded and planted in suitable vegetation for the disposal of runoff water without erosion.

Grasses - In general, monocotyledonous, parallel-veined grasses of the botanical family Gramineae.

Green Manure - Any crop or plant grown and plowed under to improve the soil, by adding organic matter and subsequently releasing plant nutrients, especially nitrogen.

Groundwater - Water within the earth that supplies wells and springs; water in the zone of saturation where all openings in rocks and soil are filled, the upper surface of which forms the water table.

Groundwater Under the Direct Influence of Surface Water (GWUDISW) - Any water beneath the surface of the ground with either 1) significant occurrence of insects or other microorganisms, algae, or large-diameter pathogens or 2) significant and relatively rapid shifts in water characteristics such as turbidity, temperature, conductivity, or pH which closely correlate to climatological or surface water conditions. Direct influence is determined for individual sources in accordance with criteria established by a state.

Gully - A deeply eroded channel caused by the concentrated flow of water.


Handler - See Pesticide Handler.

Harmonization - The process and result or adjusting differences or inconsistencies to bring tolerances and/or pesticide registrations between different countries into agreement. Regulatory authorities benefit since compliance and enforcement will be simplified. In addition, harmonization benefits the grower, consumer, and the pesticide industry.

Health Advisory Level (HAL) - A non-regulatory health-based reference level of chemical traces (usually in ppm) in drinking water at which there are no adverse health risks when ingested over various periods of time. Such levels are established for 1 day, 10 days, long-term and lifetime exposure periods. They contain a wide margin of safety. See Maximum Contaminant Level.

Hill - To place soil up to and around crops, usually planted in rows.

Hormone - A product of living cells that circulates in the animal or plant fluids and that produces a specific effect on cell activity remote from its point of origin.

Host - A plant or animal that provides sustenance for another organism.

Hydrolysis - Breakdown of a chemical in the presence of water.

Hypoxia/Hypoxic Waters - Waters with dissolved oxygen concentrations of less than 2 ppm, the level generally accepted as the minimum required for most marine life to survive and reproduce.


Illegal Residue - (1) A quantity of pesticide remaining on or in the crop/animal at harvest/slaughter that is above the set tolerance. (2) Detection of any level of pesticide when there is no established tolerance.

Incompatibility - A condition that prevents pesticides from mixing together properly to form a uniform solution or suspension. The formation of flakes, crystals, oily clumps, or severe separation is unacceptable and may clog application equipment and limit even distribution of active ingredients in the spray tank, which prevents good pesticide coverage. Tank mixes should always be evaluated with a compatibility test before mixing.

Incorporation - Mixing of materials found on or spread upon the soil surface (e.g. fertilizers, pesticides, or crop residues) into the soil volume via tillage.

Incubation Period - The period of time between the penetration of a host plant by a pathogen and the first appearance of symptoms on the host.

Inert Ingredients - FIFRA 2(m) defines inert ingredient as "an ingredient which is not active." Inert ingredients may be solvents, carriers, perfumes, dyes, perfumes, and surfactants. They include any substance (or group of structurally similar substances) other than the active ingredient(s) that are intentionally included in a pesticide product. Inert ingredients are regulated under both FIFRA and FFDCA.

Infection - The interaction of parasite with host; the beginning of that interaction.

Infiltration - Flow of water from the land surface into the subsurface.

Infiltration Gallery - A sub-surface groundwater collection system, typically shallow in depth, constructed with open-jointed or perforated pipes that discharge collected water into a watertight chamber from which the water is pumped to treatment facilities and into the distribution system. Usually located close to streams or ponds.

Ingredient Statement - The portion of the label on a pesticide container that gives the name and amount of each active ingredient and the total amount of inert ingredients in the formulation.

Inhalation Toxicity - The ability of a pesticide to harm humans or animals when breathed in through the nose and mouth into the lungs.

Injection Well - As defined by the U.S. EPA, any bored, drilled or driven shaft, dug pit, or hole in the ground into which waste or fluid is discharged, and any associated subsurface appurtenances, the depth of which is greater than the largest surface dimension of the shaft, pit, or hole.

In-Line Filtration - Pre-treatment method in which chemicals are mixed by the flowing water; commonly used in pressure filtration installations. Eliminates need for flocculation and sedimentation.

Inoculum - That part of a pathogen that can cause disease in a host.

In-row Subsoiling - Use of subsoiling in conjunction with traffic control or where the subsoiler tool is an integral part of the planter implement, for the purpose of having zones of maximum soil shattering located directly beneath the planted row in order to maximize root exploration or penetration of a restrictive zone shattered by the subsoiling operation.

Insects - Arthropods characterized by a body composed of three segments and three pairs of legs.

Integrated Pest Management (IPM) - The use of all suitable pest control methods to keep pest populations below the economic injury level. Methods include cultural practices; use of biological, physical, and genetic control agents; and the selective use of pesticides.

Intercropping - The growing of two crops simultaneously in the same field.

Inter-Regional Project 4 (IR-4) - A federal-state agricultural research collaboration headquartered at Rutgers University that was established by the USDA and the State Agricultural Experiment Station Directors in 1963. Since its beginnings, it has been the primary entity generating research data to allow registration of pest-management products for specialty crop growers and for minor uses on major crops.

Interseeding - Seeding between sod plugs, sod strips, rows, or sprigs, or seeding into turf to improve the stand or alter its composition.

Invasive Species - Species that are imported into a new ecosystem, either accidentally or intentionally, from their original ecosystem. They can out-compete native species as the invaders often do not have predators or other factors to keep them in check. The zebra mussel in the Great Lakes is an example of an invasive species.

Inversion - Reversal of vertical order of occurrence of layers of soil. Also see Temperature Inversion.

Invertebrate - A class of animals that lack backbones. Examples include insects, spiders, nematodes, snails, and slugs.


Juvenile Hormones - Compounds, either natural or synthetic, which block development of the growing insect.


Label - The written, printed, or graphic matter on, or attached to, the pesticide or device or any of its containers or wrappers.

Labeling - All labels and all other written, printed, or graphic matter (a) accompanying the pesticide or device at any time or (b) to which reference is made on or in literature accompanying the pesticide or device, except current official publications of Federal or State agencies.

Land Forming - Tillage operations which move soil to create desired soil configurations. Forming may be done on a large scale such as gully filling or terracing, or on a small scale such as contouring, ridging, or bedding.

Larvae - Immature forms of insects that undergo complete metamorphosis; developmental stages are egg, larva, pupa, and adult.

LC50 - The concentration of a pesticide, usually in air or water, that can kill 50% of a population of test animals. LC50 is usually expressed in parts per million (ppm). The lower the LC50 value, the more acutely toxic the chemical. Also called median lethal concentration.

LD50 - The dose or amount of a pesticide that can kill 50% of a population of test animals when eaten or absorbed through the skin. LD50 is expressed in milligrams of chemical per kilogram of body weight (mg/kg) of the test animal. The lower the LD50 value, the more acutely toxic the chemical. Also called median lethal dose.

Leaching - The movement through soil of a pesticide or other chemical that is dissolved in water.

Lesion - A localized area of diseased or damaged tissue.

Life Cycle - The series of stages that an organism passes through during its life. Many pest species, both plants and animals, pass through several life stages during which their susceptibility to or tolerance of pesticides varies greatly.

Lifetime Exposure - Total amount of exposure to a substance that a human would receive in a lifetime (usually assumed to be 70 years).

Limit of Detection (LOD) - The minimum concentration of a substance being analyzed that has a 99 percent probability of being identified.

Lowest Observed Adverse-Effect Level (LOAEL) - Lowest concentration or amount of a substance (dose), found by experiment or observation, which causes an adverse effect on morphology, functional capacity, growth, development, or life-span of a target organism distinguishable from normal (control) organisms of the same species and strain under defined conditions of exposure.


Mandatory Statements - Label directions that a pesticide handler must follow to legally use the pesticide.

Margin of Exposure (MOE) - The ratio of the no observed adverse effect level (NOAEL) to the estimated exposure dose.

Margin of Safety (MOS) - Ratio of the highest estimated or actual level of exposure to an agent (e.g., pesticide) and the highest nontoxic dose threshold (usually the NOEC or NOEL).

Market Basket Survey - Pesticide residue monitoring on a wide range of food items collected from consumer points of sale and in proportions approximating consumption patterns in the local population.

Maximum Contaminant Level (MCL) - The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to the MCLG as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards. See Health Advisory Level.

Maximum Contaminant Level Goal (MCLG) - Under the Safe Drinking Water Act, a non-enforceable concentration of a drinking water contaminant, set at the level at which no known or anticipated adverse effects on human health occur and which allows an adequate safety margin. The MCLG is usually the starting point for determining the regulated Maximum Contaminant Level.

Maximum Residue Level (MRL) - Comparable to a U.S. tolerance level, the enforceable limit on food pesticide levels in some countries. Levels are set by the Codex Alimentarius Commission, a United Nations agency managed and funded jointly by the World Health Organization and the Food and Agriculture Organization. See Tolerance (2).

Mechanical Weed Control - Physical control of weeds by using implements ranging from the hoe to large field cultivators.

Median Lethal Concentration - See LC50.

Median Lethal Dose - See LD50.

Mesotrophic Lakes - Lakes in transition between oligotrophic and eutrophic lakes.

Metabolite - In pesticides, a compound derived from changes in the active ingredient through chemical, biological, or physical reactions. The metabolite may be simpler or more complex and may or may not be more toxic than the original chemical.

Metamorphosis - A change in the shape, size, and/or form of animals as they develop from eggs to adults.

Microbial Degradation - Breakdown of a chemical by microorganisms.

Minimum Tillage - The minimum use of primary and/or secondary tillage necessary for meeting crop production requirements under the existing soil and climatic conditions, usually resulting in fewer tillage operations than for conventional tillage.

Minor Use - The use of a pesticide on an animal, on a commercial agricultural crop or site, or for the protection of public health where: (1) the total United States acreage for the crop is less than 300,000 acres, as determined by the Secretary of Agriculture; or (2) EPA, in consultation with USDA, determines that, based on information provided by an applicant for registration or a registrant, the use does not provide sufficient economic incentive to support the initial registration or continuing registration of a pesticide for such use and — (a) there are insufficient efficacious alternative registered pesticides available for the use; (b) the alternatives to the pesticide use pose greater risks to the environment or human health; (c) the minor use pesticide plays or will play a significant part in managing pest resistance; or (d) the minor use pesticide plays or will play a significant part in an integrated pest management program.

Miscible Liquids - Two or more liquids capable of being mixed in any proportions and of remaining mixed under normal conditions. Water and ethyl alcohol are miscible; water and oil are not.

Mite - A small arthropod similar to an insect but with eight legs, two body parts, and no antennae.

Mode of Action (MOA) - The way in which a pesticide affects the target plant, animal, or microorganism.

Molting - In invertebrates (such as insects, spiders, and mites), the process of shedding the outer body covering or exoskeleton. Molting allows the animal to grow larger.

Monitoring Well - A well that is used to obtain water quality samples or measure groundwater levels.

Monoclonal Antibodies (MABs) - Single species of immunoglobulin molecules produced by culturing a single clone of a hybridoma cell. MABs recognize only one chemical structure, i.e., they are directed against a single epitope of the antigenic substance used to raise the antibody. MABs are commonly used in immunoassays (e.g., ELISA test kits) to identify and characterize pesticide residues or metabolites within complex matrices (e.g., ground water, soil, etc.).

Municipal Water System - See Public Water System.

Mutagen - Agent that can induce heritable changes (mutations) of the genotype in a cell as a consequence of alterations or loss of genetic material.

Mycelium - The mass of filaments that forms the body of a fungus.

Mycoplasma - A genus of various extremely small bacteria that lack cell walls, are usually non-motile, and are often pathogenic or parasitic.

Mycotoxin - A toxin produced by a fungus under special conditions of moisture and temperature. Mycotoxins are common contaminants of harvested food and feed crops which can have dramatic adverse effects on humans and animals.


NAFTA Minor Use Joint Reviews - EPA and Health Canada Pest Management Regulatory Agency (PMRA) worked together to develop a registration process that will permit a regulatory decision of pesticide uses for the minor use grower communities in both countries simultaneously.

National Estuary Program - A program established under the Clean Water Act Amendments of 1987 to conserve and manage estuaries, restore and maintain their chemical, physical, and biological integrity, and control point and non-point pollution sources.

National Institute for Occupational Safety and Health (NIOSH) - A federal agency that conducts research on health and safety concerns, tests and certifies respirators, and trains occupational safety and health professionals.

Necrosis - Localized death of cells or tissues.

Nematodes - More or less elongate, spindle-shaped, worm-like animals ranging in size from less than a millimeter to several meters in length, living as saprophytes in soil or water or as parasites of plants or animals.

Neurotoxin - A substance or agent able to cause disorders of the nervous system.

Nitrogen Fixation - The process in which bacteria convert biologically unusable nitrogen gas (N2) into biologically usable ammonia (NH3) and nitrates (NO3-)

Non-Community Water System - A public water system that has at least 15 connections used by travelers or transients at least 60 days a year or serves 25 or more people daily for at least 60 days a year. Examples include separate water systems which serve motels, restaurants, campgrounds, etc.

Non-Point Source (NPS) Pollution discharged over a wide land area, not from one specific location. These are forms of diffuse pollution caused by sediment, nutrients, organic and toxic substances originating from land-use activities, which are carried to lakes and streams by surface runoff. Non-point source pollution is contamination that occurs when rainwater, snowmelt, or irrigation washes off plowed fields, city streets, or suburban backyards. As this runoff moves across the land surface, it picks up soil particles and pollutants, such as nutrients and pesticides. Compare to Point Source Pollution.

Nonporous - Something which does not allow water or air to pass through it.

Non-Potable Water - Water that is unsafe or unpalatable to drink because it contains pollutants, contaminants, minerals, or infective agents.

Non-Target Organism - Organism unintentionally exposed to a pesticide, although not an intended object of its use, which could be affected by the pesticide.

Non-Transient Non-Community Water System (NTNCWS) - A public water system that is not a community water system and regularly serves at least 25 of the same persons per day over six months per year.

No Observed Adverse Effects Concentration (NOAEC) - The highest level of a chemical stressor in a toxicity test that did not cause harmful effect in a plant or animal. While NOAELs and NOAECs are similar, they are not interchangeable. A NOAEL refers to a dose of chemical that is ingested, while a NOAEC refers to direct exposure to a chemical (e.g., through gills or the skin).

No Observed Adverse Effects Level (NOAEL) - An exposure level at which there are no statistically or biologically significant increases in the frequency or severity of adverse effects between the exposed population and its appropriate control; some effects may be produced at this level, but they are not considered as adverse, or as precursors to adverse effects. In an experiment with several NOAELs, the regulatory focus is primarily on the highest one, leading to the common usage of the term NOAEL as the highest exposure without adverse effects.

No Observed Effects Level (NOEL) - An exposure level at which there are no statistically or biologically significant increases in the frequency or severity of any effect between the exposed population and its appropriate control.

Noxious weed - A plant defined by law as being particularly troublesome, undesirable, and difficult to control.

Nozzles - Atomizing devices attached to sprayers that produce droplets that form the spray pattern.

Nymph - The developmental state of insects with gradual metamorphosis that hatch from the egg. Nymphs become adults.


Occasional Pest - An organism that causes intermittent damage as a result of changing environmental conditions or fluctuations in populations of natural enemies.

Occupational Safety and Health Administration (OSHA) - A federal agency that issues and enforces regulations for workplace health and safety.

Office of Pesticide Programs (OPP) - The Office of Pesticide Programs (OPP) regulates the use of all pesticides in the United States and establishes maximum levels for pesticide residues in food, thereby safeguarding the nation's food supply. See

Office of Prevention, Pesticides, and Toxic Substances (OPPTS) - EPA's Office of Prevention, Pesticides and Toxic Substance (OPPTS) plays an important role in protecting public health and the environment from potential risk from toxic chemicals for now and for generations to come. OPPTS promotes pollution prevention and the public's right to know about chemical risks. See

Offsite - Outside the target area of a pesticide application.

Oligotrophic Lakes - Low in biological productivity and total nutrient availability, these are typically deep, cold lakes with limited phytoplankton. The evolution of natural lakes is normally from oligotrophic to eutrophic. Some lakes, such as glacial lakes or very large, deep lakes, remain oligotrophic; however, human activity has caused an acceleration of eutrophication even for lakes that would normally remain oligotrophic. See Eutrophic Lakes.

Oncogen - A substance or agent able to induce tumors (not necessarily cancerous) in living tissues.

Oral Toxicity - Toxicity of a compound when given by mouth. Usually expressed as number of milligrams of chemical per kilogram of body weight of animal (white rat) when given orally in a single dose that kills 50 percent of the animals. The smaller the number, the greater the toxicity. See LD50.

Organic Farming - "Organically grown" food is grown and processed using no synthetic fertilizers or pesticides. Pesticides derived from natural sources (such as biological pesticides) may be used in producing organically grown food. The Organic Foods Production Act of 1990 requires the Secretary of Agriculture to establish a National List of Allowed and Prohibited Substances. This list identifies synthetic substances that may be used, and the non-synthetic substances that cannot be used, in organic production and handling operations. The Organic Materials Review Institute (OMRI) is an international nonprofit organization that determines which input products are allowed for use in organic production and processing.

Organic Matter - Plant and animal residues, or substances made by living organisms. All are based upon carbon compounds.

Organophosphate (OP) Alternative - A conventional pesticide use that represents a significant alternative to a chemical or chemicals belonging to the organophosphate (OP) class of insecticides. OPs are a group of closely related pesticides used in agriculture and non-agricultural sites that affect functioning of the nervous system. They were among EPA’s first priority group of pesticides to be reviewed under the Food Quality Protection Act.

Organophosphates - A large group of pesticides that contain the element phosphorus. Most are non-persistent insecticides, miticides, and nematicides. Many are highly toxic. Examples include malathion, parathion, diazinon, and chlorpyrifos.

Overland Flow - A land application technique that cleanses wastewater by allowing it to flow over a sloped surface. As the water flows over the surface, contaminants are absorbed and the water is collected at the bottom of the slope for reuse.

Overseeding - Seeding into an existing turf. Winter overseeding means seeding cool-season turfgrasses over warm-season turfgrasses at or near their start of winter dormancy; it is used in mild climates to provide green, growing turf during the winter period when the warm-season species are brown and dormant.

Overwintering / Oversummering - How a pathogen survives during low winter temperatures and/or the hot, dry weather of summer, whether host plants are actively growing or dormant. For example, fungi and bacteria may survive in infected plant tissues, including fallen leaves and fruit, as resting or other spores, as sclerotia, in soil, in seeds or other propagative parts such as tubers, or on another or alternate host. Viruses may survive in insect or nematode hosts. Some nematodes may survive as eggs or cysts in the soil.

Oxidizer - A highly reactive chemical that is potentially explosive and a fire hazard under certain conditions.


Parasite - An organism living in or on another living organism (host) from which it extracts nutrients.

Particle Drift - The airborne movement of particles such as pesticide dusts and pesticide-contaminated soil from the application site.

Particulate Matter - A suspension of fine solid or liquid particles in air, such as dust, fog, fume, mist, smoke, or sprays.

Pathogen - A disease-producing agent; usually applied to a living organism. Generally, any viruses, bacteria, or fungi that cause disease.

Penetrant - (1) An adjuvant added to a spray mixture to enhance the absorption of a pesticide. (2) Oil added to a spray to enable it to penetrate the waxy insect cuticle more effectively.

Percolation - The movement of water through the subsurface soil layers, usually continuing downward to the groundwater or water table reservoirs.

Perennial - A plant which lives for many years and does not die after flowering. All perennials have underground parts that store food over the winter and allow them to reemerge in the spring. One way to tell if a weed is a perennial is to dig it up and look for these underground parts.

Permeability - The ease with which water and dissolved pesticides can flow through porous materials, such as soil, gravel, or sand.

Persistence - The term applied to chemicals that remain active for a long period of time after application.

Personal Protective Equipment (PPE) - Any chemical-protective clothing or device placed on the body to prevent contact with, and exposure to, an identified chemical substance or substances in the work area. Examples include, but are not limited to, chemical-protective clothing, aprons, hoods, chemical goggles, face splash shields, or equivalent eye protection, and various types of respirators. Barrier creams are not included in this definition. Pesticide labels indicate what types of PPE are required.

Pest - An undesirable organism (e.g., insect, bacterium, fungus, nematode, weed, virus, or rodent) that injures or harms humans, desirable plants or animals, manufactured products, or natural products.

Pesticidal Pollution - Pesticides affecting the environment in undesirable ways, including effects on non-target organisms (plants, wildlife, humans, etc.) or sites (lakes, rivers, groundwater, etc.) through over-application, drift, carryover, run-off, and leaching. Many stewardship practices involving farm management and pesticide handling can reduce the potential for contamination. Many stewardship techniques prevent or minimize pollution, such as integrated pest management; careful selection, measuring, mixing, loading, disposal, and storage of pesticides; accurate calibration and maintenance of application equipment; careful consideration of the vulnerability of the area; proper location and upkeep of wells; use of best management practices; and delaying application if heavy or sustained rain is predicted.

Pesticide - Substance or mixture of substances intended for preventing, destroying, or controlling any pest, including vectors of human or animal disease, unwanted species of plants or animals causing harm or otherwise interfering with the production, processing, storage, transport, or marketing of food, agricultural commodities, wood, wood products, or animal feedstuffs, or which may be administered to animals for the control of insects, mites/spider mites, or other pests in or on their bodies. The term includes substances intended for use as a plant growth regulator, defoliant, desiccant, or agent for thinning fruit or preventing the premature fall of fruit, and substances applied to crops either before or after harvest to protect the commodity from deterioration during storage or transport.

Pesticide Application Types - Pesticide applications can be classified by timing, location, or both.

  • Aerial Application - Pesticide treatment applied from the air, usually with the use of an airplane or helicopter.
  • Band(ed) Application – A pesticide or other material applied in or beside a crop row instead of over the entire field. It is done at planting over a closed seed furrow, post-plant over the row, or post-emergent, often as a side-dress application. They are usually superficially incorporated into the soil with drag chains or tines.
  • Basal Application – Herbicide application directed to the lower portions of plant stems or trunks.
  • Broadcast Application – Application of a pesticide made uniformly to an entire area or field.
  • Chemigation – The application of pesticides or fertilizers to a target site in irrigation water. Also known as injector systems when used in greenhouses.
  • Crack-and-Crevice Application – Placement of small amounts of pesticide into cracks and crevices in buildings, such as along baseboards and in cabinets, where pests commonly hide or enter a structure.
  • Delayed Dormant Application - An application made when a plant, typically a fruiting tree, is still dormant but about to enter the pre-bloom stage.
  • Directed Application - A pesticide precisely applied to a specific area or site. Examples include a basal application to woody plants or a crack-and-crevice treatment in a building.
  • Directed Band Application - An application made in a continuous narrow strip while contacting no more than the lower part of the stems of row crops.
  • Directed-Spray Application – Specifically targeting pests to minimize pesticide contact with non-target plants and animals.
  • Dormant Spray - A pesticide application made in late winter or early spring before plants resume active growth.
  • Drip Application - Slow, monitored release of pesticide through drip irrigation equipment to conserve water.
  • Early Pre-Plant (EPP) - Herbicide application two weeks or more before planting the crop. Products that can be applied early pre-plant as well as pre-plant and pre-emergence give the grower a wider application window, making adverse weather conditions like rainy weather less likely to hinder or prevent an application. Stewardship is also aided by products that give growers the flexibility to wait instead of spraying prior to adverse weather conditions such as heavy rain.
  • Fall Pre-Plant Application – Herbicide application made in the fall, prior to planting the crop the following spring. Timing is critical relative to soil freeze-up, to ensure that product does not degrade or move in the environment during the fall or winter months.
  • Fog Treatment – The application of a pesticide as a fine mist or fog.
  • Foliar Application – Application of a pesticide to the leaves or foliage of plants.
  • Frill Treatment - Placement of herbicide into a series of overlapping axe cuts made through the bark in a ring around the trunk of a tree.
  • Fumigation - The application of smoke, vapor, or gas for the purpose of disinfecting or destroying pests or microorganisms.
  • Incorporated - A pesticide application that is mixed into the soil mechanically or by irrigation, to improve control of soil organisms or germinating weeds, or reduce the pesticide's loss by surface runoff, volatility, and/or photodecomposition. However, this practice may increase the amount of pesticide that leaches through the soil.
  • In-Furrow Application – Application done at planting where the granules or liquids are applied into an open seed furrow just before it is closed by the press wheel.
  • Non-Incorporated - A pesticide application to the soil surface, which enters the soil only by rainfall.
  • Post-Emergence (Post) Application - Application after emergence of the specified weed or crop. Usually used to specify the timing of herbicide applications.
  • Post-Harvest Application – (1) An application of an insecticide or fungicide to the harvested commodity prior to or in storage. (2) An application of herbicide to fallow (unplanted) ground after crop harvest.
  • Pre-emergence (Pre) Application - Application of a pesticide before the weed or crop plants have appeared through the soil, usually used to specify the timing of herbicide applications.
  • Pre-Plant Application – Application made before planting or transplanting a crop, either as a foliar application to control existing vegetation or as a soil application. Most commonly refers to herbicides. The application is usually broadcast over the entire field.
  • Pre-Plant Incorporated (PPI) Application – Pre-plant application that is broadcast over the entire field and incorporated.
  • Rope-Wick / Wiper Treatments – An application in which a pesticide is released onto a device that is wiped onto weeds taller than the crop, or wiped selectively onto individual weeds.
  • Soil Application – Application of a pesticide directly on or in the soil instead of on a growing plant.
  • Soil Drench – Applying a chemical mixed with water to the soil around the base of a tree so that its roots can absorb the chemical. Soil drenches are commonly used to apply water-soluble systemic insecticides or fungicides to combat pests or diseases attacking a tree. Soil drenches are most beneficial against boring insects, root rots and other problems that are difficult to treat with chemicals applied to the leaves and stems.
  • Soil Incorporation – Use of tillage, rainfall, or irrigation equipment to move pesticide into the soil.
  • Soil Injection – The placement of a pesticide under pressure below the surface of the soil. This is a common application method for fumigants and termiticides.
  • Space Spray (Space Treatment) – A pesticide applied as a fine spray or mist to a confined area.
  • Spot Treatment – An application to a small, localized area where pests are found.
  • Sub-Slab Injection – Technique used for treating soil beneath foundation slabs for the control of subterranean termites.
  • T-Band – A banded application at planting over an open seed furrow.
  • Tree Injection – Application of pesticides under the bark of trees.

Pesticide Formulation - Pesticide product offered for sale. It generally consists of active ingredient(s), adjuvant(s), and other inert ingredients combined to render the product useful and effective for the purpose claimed.

Pesticide Formulation Types - Pesticides are formulated in different ways based on their solubility characteristics and their intended uses.

  • Aerosol – A chemical stored in a container under pressure. An extremely fine mist is produced when the material, dissolved in a liquid, is released into the air.
  • Bait – Active ingredient mixed with food or other attractive substance. Pests are killed by eating the bait that contains the pesticide. Baits are available in dry or liquid forms.
  • Dispersible Granule (DG) - Dry granular pesticide formulation that will separate or disperse to form a suspension when added to water.
  • Dry Flowable (DF) – See Water-Dispersible Granule.
  • Dust - A finely ground, dry pesticide formulation containing a small amount of active ingredient and a large amount of inert carrier or diluent, such as clay or talc.
  • Emulsifiable Concentrate (EC) – A pesticide formulation produced by mixing an active ingredient and an emulsifying agent in a suitable petroleum solvent. When combined with water, a milky emulsion is usually formed.
  • Flowable – A pesticide formulation in which a very finely ground solid particle, composed of both active and inert ingredients, is suspended in a liquid carrier. These formulations are mixed with water before spraying.
  • Granule or Granular – A dry pesticide formulation in which the active ingredient is either mixed with or coated onto an inert carrier to form a small, ready-to-use, low-concentrate particle that is not normally a drift hazard. Pellets differ from granules only in their precise uniformity, larger size, and shape.
  • Invert Emulsion – A mixture in which water droplets are suspended in an oil instead of oil droplets being suspended in water.
  • Microencapsulated Pesticide – A formulation in which the pesticide active ingredient is encased in plastic capsules. When the capsules start to break down after application, the pesticide is slowly released.
  • Pastes and Gels – Formulations commonly used in the pest-control industry for controlling ants and cockroaches.
  • Pellet – A pesticide formulation consisting of dry active and inert ingredients pressed into a uniformly sized and shaped ready-to-use material. Pellets are larger than granules.
  • Ready-to-Use (RTU) – Low-concentrate formulations that require no further dilution before application.
  • Soluble Concentrate (SC) - Liquid formulation that forms a solution when added to water.
  • Soluble Powder – Powder formulation that dissolves readily in water and forms a true solution that requires no additional agitation after mixing. Few pesticides are available in this formulation because few active ingredients are readily soluble in water.
  • Suspension – A pesticide mixture consisting of fine particles dispersed or floating in a liquid, usually water or oil. Examples include wettable powders or flowables in water.
  • Water-Dispersible Granule (WDG) – A dry, granular formulation that breaks apart and disperses to form a suspension when added to water.
  • Water-Soluble Concentrate – A liquid pesticide formulation that dissolves in water to form a true solution.
  • Water-Soluble Packet – Wettable powder or soluble powder formulation packaged in a special type of plastic bag that dissolves and releases its contents when placed in water.
  • Wettable Powder (WP) - Pesticide formulation of active ingredient mixed with inert dust and a wetting agent that mixes readily with water and forms a short-term suspension (requires tank agitation).

Pesticide Handler - A person who works directly with pesticides, such as during mixing, loading, transporting, cleaning, storing, disposing, and applying, or who repairs pesticide application equipment.

Pesticide Registration Notice (PR Notice) - Pesticide Registration Notices are issued by EPA’s Office of Pesticide Programs to inform pesticide registrants and other interested persons about important policies, procedures, and regulatory decisions. They do not create new legally binding requirements. Each PR Notice is given a unique number that identifies it according to both the year and the sequence of issue within the year of issue. For example "PR Notice 98-7" was the 7th notice issued in 1998.

Pesticide Stewardship - The careful and responsible management of pesticides, which results in protection of the environment and people and extension of pesticide product life.

Pesticide Types - Pesticides can be grouped in many ways, such as by their target pests, their spectrum of activity, the source of the active ingredient, etc.

  • Biochemical Pesticides - Chemicals that are either naturally occurring or identical to naturally occurring substances such as hormones, pheromones, and enzymes. Biochemicals function as pesticides through non-toxic, non-lethal modes of action, such as disrupting the mating pattern of insects, regulating growth, or acting as repellants. Since biochemicals tend to be environmentally compatible, they are important to Integrated Pest Management programs.
  • Biopesticide - A pest control product derived from such natural materials as animals, plants, bacteria, and certain minerals. Biopesticides fall into three major classes: (1) Microbial pesticides, (2) Plant-Incorporated-Protectants (PIPs), (3) Biochemical pesticides.
  • Botanical Pesticide - A pest control product produced from naturally occurring chemicals in plants. Examples include nicotine, pyrethrum, and rotenone.
  • Broad-Spectrum Pesticide - A pest control product that is effective against a wide range of pests.
  • Contact Herbicide - Herbicide that causes injury to only the plant tissue to which it is applied or which is not appreciably translocated within plants.
  • Curative Pesticide - A pest control product that can inhibit or kill a disease-causing organism after it is established in the plant or animal.
  • Defoliant - A chemical that initiates the premature drop of leaves, often as an aid in harvesting a crop, e.g., cotton plants may be defoliated with paraquat prior to harvest.
  • Desiccant - (1) A chemical that promotes drying or loss of moisture from leaves or other plant parts. (2) A chemical that removes water from arthropods or destroys the waxy covering that protects these organisms from water loss.
  • Fumigant - Liquid or solid chemical that forms vapors that kill organisms. Fumigants are often used in the treatment of areas difficult to penetrate with sprays or other pesticidal formulations, such as in structural pest control in food- and grain-storage facilities, in regulatory pest control, in soil, in greenhouses, and in granaries and grain bins.
  • Fungicide - A chemical used to control fungi.
  • General-Use Pesticide - A pest control product that can be purchased and used by the public.
  • Generic Pesticide - Pesticide for which the original manufacturer’s patent on the active ingredient has expired in a certain geographic area and production is now also occurring via one or more secondary manufacturers.
  • Growth Regulator - Chemical, often a natural or synthetic hormone, used to modify or regulate the growth and development of a plant or insect, sometimes for the purpose of control. See also Insect Growth Regulator.
  • Harvest Aid Chemical - A chemical material applied to a plant before harvest to reduce the amount of plant foliage.
  • Inorganic Pesticides - Pest control products of mineral origin that do not contain carbon.
  • Insect Growth Regulator (IGR) - A type of insecticide that controls certain insects by disrupting their normal growth process from immature to adult.
  • Insecticide - A pesticide used to control or prevent damage caused by insects and related arthropods.
  • Larvicide - A pesticide used to kill insect larvae. Commonly used to control mosquito and black fly larvae.
  • Microbial Pesticide - Microorganism that is used to control a pest. A common one is Bt, which contains the spores and toxic crystals of the naturally occurring bacteria Bacillus thuringiensis.
  • Minimum-Risk Pesticides - Products that pose a minimal risk to humans and the environment and thus are exempt from federal registration.
  • Miticide - A pesticide used to control mites.
  • Narrow-Spectrum Pesticide - A pest control product that is effective against only one or a few species of pests. Usually associated with insecticides and fungicides.
  • Nematicide - A pesticide used to control nematodes.
  • Non-Persistent Pesticide - A pest control product that does not remain active in the environment more than one growing season.
  • Non-Selective Pesticide - A pest control product that is toxic to a wide range of plants or animals without regard to species. For example, a non-selective herbicide can kill or damage all plants it contacts.
  • Ovicide - A material that destroys eggs.
  • Persistent Pesticide - A pesticide chemical (or its metabolites) that remains active in the environment more than one growing season. Some compounds can accumulate in animal and plant tissues or remain in the soil for years.
  • Plant Growth Regulator (PGR) - A pesticide used to regulate or alter the normal growth of plants or the development of their parts.
  • Plant-Incorporated Protectants - Pesticidal substances and the genetic material needed to produce them by plants that have been genetically modified so the plant is protected from certain insect pests. For example, scientists can take the gene for the Bt pesticidal protein from the bacterium and introduce that gene into the plant's own genetic material. Then the plant manufactures the substance that destroys the pest. EPA regulates the protein and its genetic material, but not the plant itself. It also includes any inert ingredient contained in the plant, or product thereof. A peer review by the FIFRA Science Advisory Panel (SAP) may or may not be required for a given action -- this is determined on a case-by-case basis.
  • Protectant - A pesticide applied to a plant or animal before infection or attack by a pest to prevent infection or injury by the pest. See also Seed Protectant.
  • Pyrethroid - A synthetic insecticide that mimics pyrethrin, a naturally occurring pesticide derived from certain species of chrysanthemum flowers.
  • Reduced-Risk Pesticide - Pesticide product, the use of which yields comparatively lower risks to human health and/or the environment than others generally available. Advantages of reduced-risk pesticides include: low impact on human health, lower toxicity to non-target organisms (birds, fish, and plants), low potential for groundwater contamination, low use rates, low pest-resistance potential, and compatibility with IPM practices.
  • Residual Pesticide - A pest control product that remains effective on a treated surface or area for an extended period following application.
  • Restricted-Use Pesticide - A pesticide that can be applied only by certified applicators, because of its inherent toxicity or potential hazard to the environment.
  • Seed Protectant - A pesticide applied to seeds before planting to protect them from insects, fungi, and other soil pests.
  • Selective Herbicide - Chemical that is more toxic to some plant species than to others. Kills or significantly retards growth of an unwanted plant species without significantly damaging desired plant species.
  • Selective Pesticide - A pest control product that is toxic to some pests but has little or no effect on other, similar species. Examples include some fungicides that control only powdery mildews and no other fungi.
  • Soil Fumigant - Pesticide that, when applied to soil, form a gas to control pests that live in the soil and can disrupt plant growth and crop production. Soil fumigants are used on many high-value crops and provide benefits to growers in controlling a wide range of pests, including nematodes, fungi, bacteria, insects, and weeds. As gases, however, fumigants move from the soil to the air at the application site and may move off site at concentrations that produce adverse health effects in people from hours to days after application. These health effects range from mild and reversible eye irritation to more severe and irreversible effects, depending on the fumigant and the level of exposure. EPA has implemented important safety measures to increase protection for agricultural workers and bystanders.
  • Soil Residual Pesticide - A chemical or agent that prevents the growth of all organisms present in the soil; a nonselective pesticide. Soil persistence may be temporary or permanent, depending on the chemical.
  • Stomach Poison - A pesticide that must be eaten by an animal to be effective (does not kill on contact).
  • Systemic (Translocated) Pesticide - A pesticide that moves inside a plant through absorption; the movement is usually upward and outward. There are systemic insecticides, fungicides, and herbicides.
  • Termiticide - An insecticide used to control termites.

Pesticide Volatilization - Volatilization occurs when pesticide surface residues change from a solid or liquid to a gas or vapor after a pesticide application. Once airborne, volatile pesticides can come into contact with applicators or move long distances off site. Not all pesticides are volatile, and the higher the vapor pressure of a given chemical, the higher its volatility will be. Some environmental conditions (high temperature, low relative humidity, air movement, wet soil) increase volatilization. A pesticide tightly adsorbed to soil particles is less likely to volatilize; thus, soil texture, organic matter content, and soil moisture influence pesticide volatilization. Labels often provide warnings if there is a volatility hazard under certain conditions and may suggest incorporation or irrigation within a certain time period. Low-volatile formulations are also available for some pesticides.

Pest Management - The control of pests such as insects, nematodes, plant diseases, and weeds.

Pest Management Regulatory Agency (PMRA) - The branch of Health Canada responsible for pesticide regulation in Canada, created in 1995 under authority of the Pest Control Products Act. Pesticides are stringently regulated in Canada to ensure they pose minimal risk to human health and the environment.

Petiole - The stalk that attaches the leaf blade to the stem.

pH (Soil) - potential Hydrogen ions. Acidity or alkalinity of the soil is measured by pH. The scale ranges from 0 to 14, with 0 being more acid, 7 as neutral, and greater than 7 as alkaline (basic).

Pheromone - A substance secreted by an insect to the exterior causing a specific reaction in the receiving insects.

Photodegradation - Breakdown of a chemical by sunlight.

Phytotoxicity - Chemical injury to plants.

Plasmid - In many types of prokaryotic and eukaryotic cell: a linear or covalently closed circular molecule of DNA (distinct from chromosomal DNA, mtDNA, ctDNA, or kDNA and commonly dispensable to the cell), that can replicate autonomously (i.e., independently of other replicons).

Plow Layer - The greatest depth of soil exhibiting mixing or inversion by surface tillage operations. It is always desirable to retain pesticides which reach the soil in the plow layer, where biological and chemical reactions can degrade them to simple compounds like water and carbon dioxide.

Point of Runoff - When a spray starts to run or drip from the leaves and stems of plants, or from the hair or feathers of animals.

Point-Source Pollution - The contamination of water and soil from a specific, identifiable place or location, such as a spill site or a permanent mixing, loading, and cleaning site. Compare to Non-Point Source Pollution.

Pollinator - Animals or insects that transfer pollen from plant to plant. They are responsible for assisting over 80% of the world's flowering plants. Animals that assist plants in their reproduction as pollinators include species of ants, bats, bees, beetles, birds, butterflies, flies, moths, wasps, as well as other unusual animals. Wind and water also play a role in the pollination of many plants.

Porous - Something which allows water or air to pass through it.

Potable Water - Water that is safe and suitable for drinking and cooking. Compare to Safe Water.

Precautionary Statements - Labeling statements designed to provide the pesticide user with information regarding the toxicity, irritation, and sensitization hazards associated with the use of a pesticide, as well as treatment instructions and information to reduce exposure potential, including Signal Word, Child Hazard Warning, Hazards to Humans and Domestic Animals, First Aid, Personal Protective Equipment, User Safety Requirements, Engineering Controls, User Safety Recommendations, Environmental Hazards, and Physical or Chemical Hazards. These statements occur on pesticide product labels before the Directions for Use.

Precision Agriculture - A management system that is information and technology based, is site specific, and uses one or more of the following sources of data: soils, crops, nutrients, pests, moisture, or yield, for optimum profitability, sustainability, and protection of the environment.

Predator - An organism that attacks, kills, and feeds on other organisms.

Pre-Harvest Interval (PHI) - The minimum number of days between the last pesticide application and the harvest date of the crop, as allowed by the pesticide product label.

Premix - A pesticide product formulated by the manufacturer with more than one active ingredient.

Pressure Rinse - The process of decontaminating an empty pesticide container with water by using a special high-pressure nozzle to rinse the container.

Primary Infection - The first infection of a plant by the overwintering or oversummering pathogen.

Primary Inoculum - The overwintering or oversummering pathogen or its propagules that cause primary infection.

Private Applicator - A certified applicator who uses or supervises the use of restricted-use pesticides to produce an agricultural commodity on his or her own land, leased land, or rented land or on the lands of his or her employer.

Probable Effects Concentration (PEC) - The level of a concentration in the media (surface water, sediment, soil) to which a plant or animal is directly exposed that is likely to cause an adverse effect.

Probable Effects Level (PEL) - A chemical concentration in some item (dose) that is ingested by an organism, which is likely to cause an adverse effect. The ingested item is usually food, but can be soil, sediment, or surface water that is incidentally (accidentally) ingested.

Propagule - Any disseminative unit of an organism (e.g., a spore, a mycelial fragment, a sclerotium).

Publicly Owned Treatment Works (POTW) - A wastewater treatment plant that is owned by a state, unit of local government or Indian tribe, usually designed to treat domestic wastewaters. The term also may include devices and systems used by those entities in the storage, treatment, recycling, and reclamation of municipal sewage or liquid industrial wastes.

Public Policy - An attempt by a government to address a public issue by instituting laws, regulations, decisions, or actions pertinent to the problem at hand.

Public Water System (PWS) - A system for the provision to the public of water for human consumption through pipes or other constructed conveyances, that has at least 5 service connections or which regularly serves at least 25 individuals for 60 days. Also called a municipal water system.

Pump - A device that moves liquid pesticide through hoses and out of the spraying system.

Pupa - A developmental stage of insects that undergo complete metamorphosis that occurs between the larva and the adult.


Qualitative Use Assessment - Report summarizing the major uses of a pesticide including percentage of crop treated and amount of pesticide used on a site.

Quarantine - A regulatory method to prevent the introduction and dissemination of plant and animal pests into new areas. Involves inspections, treatments, and destruction of contaminated plants and animals or their parts.


Raw Agricultural Commodity (RAC) - Part of a crop used as a food or feed commodity directly from the harvested crop without processing.

Raw Water - Intake water prior to any treatment or use.

Reasonable Maximum Exposure - The maximum exposure reasonably expected to occur in a population.

Reasonable Worst Case - A semi-quantitative term referring to the lower portion of the high end of the exposure, dose, or risk distribution. The reasonable worst case has historically been loosely defined, including synonymously with maximum exposure or worst case. As a semi-quantitative term, it is sometimes useful to refer to individual exposures, doses, or risks that, while in the high end of the distribution, are not in the extreme tail. For consistency, it should refer to a range that can conceptually be described as above the 90th percentile in the distribution, but below about the 98th percentile.

Recharge - The periodic natural replacement of groundwater resources.

Recharge Rate - The quantity of water per unit of time that replenishes or refills an aquifer.

Recharge Zone - The area where a formation allows available water to enter the aquifer.

Recombinant Bacteria - A microorganism whose genetic makeup has been altered by deliberate introduction of new genetic elements. The offspring of these altered bacteria also contain these new genetic elements, i.e., they "breed true."

Recombinant DNA - The new DNA that is formed by combining pieces of DNA from different organisms or cells.

Reference Dose (RfD) - The level of exposure to a specific pesticide that a person could receive every day over a seventy-year period without significant risk of a long-term or chronic non-cancer health effect.

Registered Pesticides - Pest-control products that have been approved by the EPA in the U.S. or PMRA in Canada for the uses listed on the label.

Registrant - Organization or individual that holds the certificate of registration and is thereby responsible for a given pesticide product. A registrant can be a chemical company, government agency, importer, or any person wishing to market a pest control product within a given jurisdiction. The registrant’s name and address must appear on the product label as a legal requirement.

Registration - Pesticides are registered by EPA under Section 3 of FIFRA for use throughout the United States or for more limited use in certain states. Most pesticides are registered this way and contain an official EPA registration number. See also State-Specific Registrations.

Registration Review - An EPA program that periodically reevaluates pesticides to ensure that products currently sold are safe to use. - A U.S. Federal government web site that acts as an internet portal and document repository that allows members of the public to participate in the rulemaking processes of some Federal government agencies.

Renovation - Improvement of turf, usually involving weed control and replanting into existing live and/or dead vegetation. It does not encompass reestablishment or rebuilding.

Remediation - Cleanup or other methods used to remove or contain a toxic spill or hazardous materials from a Superfund site.

Reregistration - The re-evaluation and relicensing of existing pesticides originally registered prior to current scientific and regulatory standards. EPA reregisters pesticides through its Registration Standards Program.

Reregistration Eligibility Document (RED) - EPA’s evaluation of a pesticide database, its conclusions of the potential human health and environmental risks of current product uses, and its decision and conditions under which the uses and products will be eligible for reregistration.

Residue - Specified substances in or on food, agricultural commodities, or animal feed resulting from the use of a pesticide. The term includes any derivatives of a pesticide, such as conversion products, metabolites, reaction products, and impurities considered to be of toxicological significance. Pesticide residue includes residues from unknown or unavoidable sources as well as from known uses of the chemical.

Resistance - (1) Inheritable ability of some pest biotypes within a given population to survive a pesticide treatment that should, under normal use conditions, effectively control populations of that pest. Herbicide resistance is the inherited ability of a plant to survive and reproduce following exposure to a dose of herbicide normally lethal to the wild type. In a plant, resistance may be naturally occurring or induced by such techniques as genetic engineering or selection of variants produced by tissue culture or mutagenesis. (2) In plant pathology, it is the ability of an organism to exclude or overcome, completely or in some degree, the effect of a pathogen or other damaging factor. Compare to Tolerance (1).

Resistance Management - Use of pesticides and alternate pest control measures so as to minimize or delay the development of resistance in the target pest.

Respirator - A safety device that covers at least the mouth and nose and that protects the wearer from inhaling hazardous substances, including pesticides. Different types of respirators and other important terms having to do with respirators are listed below.

  • Chemical Cartridge / Chemical Canister - For air-purifying respirators, the type of purifying element that removes specific gases or vapors by absorbing or adsorbing them.
  • Facepiece (Tight-fitting) - A respirator that forms a complete seal with the face. Examples include particulate-filtering facepieces, half masks, and full facepiece masks.
  • Filter (HEPA) - High-efficiency particulate air filter. A high-efficiency filter is used in power air-purifying respirators. The P100 cartridge used in non-powered APRs is equivalent to a HEPA filter.
  • Filter (Particulate) - For non-powered air-purifying respirators, a purifying element that removes aerosols (solid or liquid particulates) from the air. Particulate filters are rated N, R, or P for oil degradation and 95, 99, or 100 for filtering efficiency.
  • Filter Efficiency - For air-purifying respirators, the collective efficiency of a filter to resist penetration by particulates. Non-powered APR filters are tested and rated at 95%, 99%, and 99.7% efficiency. The higher the number, the more efficient the filter. Powered APR filters are tested and rated as “high efficiency” (HE).
  • Filtering Facepiece Respirator - A type of non-powered APR in which a particulate filter is an integral part of the facepiece (or the entire facepiece is composed of the filtering medium).
  • Fit Test (Qualitative) - A method to assess whether a particular size and brand of respirator adequately fits an individual’s face using a test agent. If the person can detect inside the mask an agent that is outside the mask, there is leakage at the seal and the mask does not fit properly.
  • Fit Test (Quantitative) - A method to assess whether a particular size and brand of respirator adequately fits an individual’s face using instrumentation to numerically measure leakage into the respirator.
  • High-Efficiency Filter - See Filter (HEPA).
  • Powered Air-Purifying Respirator (PAPR) - A safety device that uses a blower to force contaminants through purifying elements.
  • Self-Contained Breathing Apparatus (SCBA) - A type of atmosphere-supplying respirator where the user carries a supply of breathable air. A pressure-demand SCBA is required when the environment is immediately dangerous to life or health (IDLH).
  • Supplied-Air (Airline) Respirator - A type of atmosphere-supplying respirator with a facepiece that delivers air through an air hose connected to a compressor, blower, or compressed-air tank. The air supply is not designed to be carried by the user.

Restricted-Entry Interval (REI) - Waiting interval required by federal law between application of certain hazardous pesticides to crops and the entrance of workers into those crops without protective clothing.

Rinsate - A liquid obtained from rinsing pesticide containers and application equipment. Rinsate from pesticide containers can be added to the spray tank. Rinsate from cleaning application equipment should be sprayed as a means of disposal. If that is not possible, the rinsate should be kept in a storage tank until it can be disposed of according to local regulations.

Riparian Buffer - Trees, shrubs and other vegetation located along the edge of rivers, streams, and other waterways that filter pollution, prevent erosion and provide wildlife habitat.

Riparian Zone - Area adjacent to a river or stream with a high density, diversity, and productivity of plant and animal species. Management of riparian zones is often used in agricultural regions as a means of protecting surface water quality from agricultural runoff. These zones act as a trap for sediments and nutrients, shade streams, thereby lowering water temperature, protect stream banks from collapse, reduce soil erosion, and provide habitat for birds, reptiles, and mammals of the region.

Risk Assessment - Process intended to calculate or estimate the risk to a given target organism, system, or (sub-) population, including the identification of attendant uncertainties, following exposure to a particular pesticide or agent of concern as well as the characteristics of the specific target system. It is the first component in a risk analysis process. The risk assessment process includes four steps: hazard identification, hazard characterization, exposure assessment, and risk characterization.

Risk Assessment - Process intended to calculate or estimate the risk to a given target organism, system, or (sub-) population, including the identification of attendant uncertainties, following exposure to a particular pesticide or agent of concern as well as the characteristics of the specific target system. It is the first component in a risk analysis process. The risk assessment process includes four steps: hazard identification, hazard characterization, exposure assessment, and risk characterization.

Risk Cup - An analogy used by EPA to describe aggregate exposure estimates, based on the concept that the total level of acceptable risk to a pesticide is represented by the pesticide’s Reference Dose (RfD). The full cup represents the total RfD; each use of the pesticide contributes a specific amount of exposure that adds a finite amount of risk to the cup. As long as the cup is not full, i.e., the combined total of all estimated sources of exposure to the pesticide has not reached 100% of the RfD, EPA can consider registering additional uses and setting new tolerances. (2) If it is shown that the risk cup is full, no new uses could be approved until the risk level is lowered. This can be done by the registrant providing new data which more accurately represent the risk or by implementing risk-mitigation measures. EPA will use similar logic to assess acute risk and cancer risk. In cases of possible exposure for which EPA has limited or no actual data (i.e., for non-dietary exposure pathways), EPA will set aside 5-20% of the risk cup based on various characteristics of the pesticide, such as toxicity, mobility and persistence in soils, and use pattern. The remainder of the risk cup will be left for dietary risk for which reliable data are available. Also see Food Quality Protection Act (FQPA).

  • Aggregate Exposure - The combined exposures to a single chemical across multiple routes (oral, dermal, inhalation) and across multiple pathways (food, drinking water, residential). FQPA requires the Office of Pesticide Programs (OPP) to make a finding for each tolerance or tolerance exemption “that there is a reasonable certainty that no harm will result from aggregate exposure to the pesticide chemical residue, including all anticipated dietary exposures and all other exposures for which there is reliable information.” There must be a reasonable certainty that no harm will result to infants and children from aggregate exposure to the pesticide chemical residues.
  • Cumulative Risk - The risk of a common toxic effect associated with concurrent exposure by all relevant pathways and routes of exposure to a group of chemicals that share a common mechanism of toxicity.

Risk to Endangered Species - EPA uses Risk Quotients (RQ) to indicate when a pesticide use as directed on the label has the potential to cause adverse effects on non-target organisms. Endangered animal species may be potentially affected by use if the acute RQ is > 0.05 for aquatic animals or > 0.1 for mammals and birds or through chronic exposure if the chronic RQ is > 1. Potential effects may be seen in endangered plant species if the RQ is > 1.

Risk to Non-Endangered Species - EPA uses Risk Quotients (RQ) to indicate when a pesticide use as directed on the label has the potential to cause adverse effects on non-target organisms.

  • Acute - An acute RQ > 0.5 for aquatic animals, mammals, and birds indicates a potential for acute risk to non-target organisms which may warrant regulatory action in addition to restricted-use classification.
  • Acute Restricted-Use - An acute RQ > 0.1 for aquatic animals or 0.2 for mammals and birds indicates a potential for acute risk to non-target organisms that may be mitigated through restricted-use classification.
  • Chronic Risk - A chronic RQ > 1 for all animals indicates a potential for chronic risk that may warrant regulatory action.
  • Non-endangered Plant Risk - RQ > 1 indicates a potential for effects.

Risk Quotient (RQ) - For most risk assessments, EPA uses a deterministic approach or the quotient method to compare toxicity to environmental exposure. In the deterministic approach, a risk quotient is calculated by dividing a point estimate of exposure by a point estimate of effects. This ratio is a simple, screening-level estimate that identifies high- or low-risk situations. (Risk Quotient = Exposure / Toxicity)

Rosette - A plant form with no central stalk, with all leaves close to the soil surface. Biennial plants form a rosette in the first year of growth.

Route of Exposure - Means by which a chemical enters an organism after contact (e.g., ingestion, inhalation, or dermal absorption.

Runoff - (1) Transport of water and sediment from the surface of an agricultural field to a non-target area such as a stream due to a precipitation event. (2) Loss of a pesticide formulation off the plant foliage during spray application, particularly at high volume. Runoff from agricultural production fields may contain residues of nutrients and pesticides that have been applied to the soil or plant canopy.


Safety Data Sheet (SDS) - An information sheet available from the manufacturer that provides details on chemical properties, toxicity, first aid, hazards, personal protective equipment, and emergency procedures to be followed in the event of a spill, leak, fire, or transportation crisis. Formerly known as Material Safety Data Sheet.

Safener - A chemical added to a pesticide to keep it from injuring plants, e.g., fluxofenim which protects sorghum crops from injury by the herbicide S-metolachlor.

Safe Water - Water that does not contain harmful bacteria, toxic materials, or chemicals, and is considered safe for drinking even if it may have taste, odor, color, and certain mineral problems. Compare to Potable Water.

Saprophyte - An organism that obtains its food from dead or decaying organic matter.

Saturated Zone - The area below the water table where all open spaces are filled with water under pressure equal to or greater than that of the atmosphere.

Scientific Name - The internationally recognized Latin name of an animal or plant species. The scientific name consists of two parts, genus and species, followed by the describer (author) of the species. The scientific names (excluding the author’s names) are always printed in italics. The genus name is always capitalized, while the specific name is not capitalized. For example, the scientific name of barley is Hordeum vulgare L., where the L. stands for Carl Linnaeus, the father of modern taxonomy.

Secondary Infection - Any infection caused by inoculum produced as a result of a primary or a subsequent infection; an infection caused by secondary inoculum.

Secondary Inoculum - Inoculum produced by infections that took place during the same growing season.

Secondary Poisoning - Harmful effects to a predatory bird or mammal that feeds on an animal killed by a pesticide.

Section 3 - See Registration.

Section 5 - See Experimental Use Permits.

Section 18 - See Emergency Exemptions.

Section 24(c) - See State-Specific Registrations.

Semi-Confined Aquifer - An aquifer partially confined by soil layers of low permeability in which recharge and discharge can still occur.

Sensitive Areas - Sites or organisms that are particularly vulnerable to harmful effects from pesticides.

Service Container - A receptacle designed to hold concentrate or diluted pesticide mixtures; not the original pesticide container.

Sheet Erosion - The removal of a relatively uniform thin layer of soil from the land surface by rainfall and largely unchanneled surface runoff (sheet flow).

Shelf Life - The maximum amount of time that a pesticide concentrate can remain in storage before losing some of its effectiveness.

Sidedress - When a readily available form of nitrogen, normally urea, is injected beside the growing row of plants, usually corn.

Signal Word - Term on pesticide label that denotes the relative acute toxicity of the product. The signal words are:

  • DANGER—POISON used with a skull and crossbones symbol for potentially lethal products
  • DANGER for severe skin and eye damage
  • WARNING for moderately toxic
  • CAUTION for slightly toxic compounds
  • A signal word is not required if all five acute toxicity studies fall into the least toxic category. If the use of a signal word is used in that case, it must be CAUTION.

Sink - Place in the environment where a compound or material collects.

Site - The crop, animal, structure, commodity, or area where a pesticide is applied.

Slurry - A thick suspension of a pesticide made from a wettable powder and water.

Soil Conditioner - An organic material like humus or compost that helps soil absorb water, build a bacterial community, and take up mineral nutrients.

Soil Conservation - Methods which reduce soil erosion and retain soil moisture. Major conservation practices include conservation tillage, crop rotation, contour farming, strip cropping, terraces, diversions, and grassed waterways.

Soil Horizon - A layer of soil or soil material approximately parallel to the land surface and differing from adjacent genetically related layers in physical, chemical, and biological properties or characteristics such as color, structure, texture, consistency, kinds and number of organisms present, degree of acidity or alkalinity, etc. Master horizons and layers are listed below.

  • O Horizons - Layers dominated by organic material.
  • A Horizons - Mineral horizons that formed at the surface or below an O horizon that exhibit obliteration of all or much of the original rock structure and (a) are characterized by an accumulation of humified organic matter intimately mixed with the mineral fraction and not dominated by properties characteristic of E or B horizons; or (b) have properties resulting from cultivation, pasturing, or similar kinds of disturbance.
  • E Horizons - Mineral horizons in which the main feature is loss of silicate clay, iron, aluminum, or some combination of these, leaving a concentration of sand and silt particles of quartz or other resistant materials.
  • B Horizons - Horizons that formed below an A, E, or O horizon that are dominated by obliteration of all or much of the original rock structure.
  • C Horizons or Layers - Horizons or layers, excluding hard bedrock, that are little affected by soil formation processes and lack properties of O, A, E, or B horizons. The material of C horizons may be either like or unlike that from which the A and B horizons presumably formed. The C horizon may have been modified even if there is no evidence of soil formation.
  • R Layers - Hard bedrock including granite, basalt, quartzite and indurated limestone or sandstone that is sufficiently coherent to make hand digging impractical.

Soil Persistence - Length of time that a pesticide application on or in soil remains effective.

Soil Texture - Relative proportion of sand, silt, and clay in the soil.

Solubility - The ability of a chemical such as a pesticide to dissolve in a solvent, usually water.

Solution - A mixture of one or more substances in another substance (usually a liquid) in which all the ingredients are completely dissolved. An example is sugar in water.

Solvent - A liquid such as water, oil, or alcohol that will dissolve another substance (solid, liquid, or gas) to form a solution.

Special Local Needs (SLN) Registration - See State-Specific Registrations.

Special Review - Formerly known as Rebuttable Presumption against Registration (RPAR), this is the regulatory process through which existing pesticides suspected of posing unreasonable risks to human health, non-target organisms, or the environment are referred for review by EPA. Such review requires an intensive risk/benefit analysis with opportunity for public comment. If risk is found to outweigh social and economic benefits, regulatory actions can be initiated, ranging from label revisions and use restrictions to cancellation or suspended registration.

Species - The basic category of biological classification, displaying a high degree of mutual similarity determined by a consensus of informed opinion; a subcategory of genus.

Specific Conductance - A measure of the ability of a water to conduct an electrical current. Specific conductance is related to the type and concentration of ions in solution and can be used for approximating the dissolved solids concentration in water.

Spore - A discrete sexual or asexual reproductive unit, usually enclosed by a rigid wall, capable of being disseminated.

Spray Deposit - The amount of pesticide chemical that remains on a sprayed surface after the droplets have dried.

Spray Drift - The off-target movement of a pesticide during a liquid application.

Sprayers - The most common type of pesticide application equipment. Many pesticides are formulated for spraying.

  • Air-Blast (Mist) Sprayer - A type of sprayer that uses both water and air as carriers. Spray droplets are formed by the nozzles under low pressure and delivered to the target by an airstream which shatters the drops into finer droplets and blows them into the target area. Air-blast sprayers are typically used for disease and insect control on fruit trees, vineyards, vegetables, and Christmas trees. Drift is a concern with this type of sprayer.
  • Ultra-Low Volume (ULV) Sprayers - The pesticide is applied at carrier volumes at ½ gallon or less per acre, often with an undiluted formulation. Sprayers may be hand-held or mounted on ground or aerial equipment. The high concentration means increased drift and safety hazards, as well as a greater risk of dosage errors.
  • Hydraulic Sprayer - A type of pesticide application equipment that uses water under pressure to deliver the pesticide to the target site.
  • Large Power-Driven Sprayers (High Pressure / Hydraulic) - Sprayers equipped to deliver large volumes of spray (20-500 GPA) under pressures ranging from 150-400+ PSI. Used to spray through dense foliage, to the tops of tall trees, etc., where high-pressure sprays are necessary for adequate penetration and reach. These sprayers may produce fine droplets that drift easily.
  • Large Power-Driven Sprayers (Low Pressure) - Sprayers designed to distribute dilute liquid pesticides over large areas. They deliver a low to moderate volume of spray (~10-60 GPA) at pressures ranging from 10-80 PSI. The low pressure limits pesticide penetration and reach.

Spreader - An adjuvant used to enhance the spread of a pesticide over a treated surface, thus improving the coverage. May also incorporate functions of a sticker. Also known as a wetting agent.

Spring - An issue of water from the earth; a natural fountain; a source of a body or reservoir of water.

Stability - The ability of a chemical such as a pesticide to resist breaking down into metabolites. A highly stable pesticide can be stored for long periods without loss of activity.

State Lead Agency (SLA) - The agency within a state or territory designated by EPA as having the authority to carry out the provisions of FIFRA.

State Management Plan - Under FIFRA, a plan required by EPA to allow states, tribes, and U.S. territories the flexibility to design and implement ways to protect groundwater from the use of certain pesticides.

State-Specific Registrations - Under Section 24(c) of FIFRA, states can register a new pesticide product for any use, or a federally registered product for an additional use, as long as there is both a demonstrated “special local need” and a tolerance, exemption from a tolerance, or other clearance under FFDCA. EPA can disapprove a state’s special local needs registration. Also called Special Local Need (SLN) Registration.

Static Water Level - Elevation or level of the water table in a well when the pump is not operating; the level or elevation to which water would rise in a tube connected to an artesian aquifer or basin in a conduit under pressure.

Sticker - An adjuvant used to improve the adherence of spray droplets to a plant, animal, or other treated surface.

Strip-Cropping (Field Strip-Cropping) - The growing of crops in a systematic arrangement of strips or bands which serve as vegetative barriers to wind and water erosion. The strips or bands may run perpendicular to the slope of the land or to the direction of prevailing winds. See also Contour Strip-Cropping.

Strip Planting (Strip-Till Planting) - A method of simultaneous tillage and planting in isolated bands of varying width, separated by bands of erect residues essentially undisturbed by tillage. An area 30 to 50 cm wide is tilled sufficiently through living mulch or standing residue to form a seedbed for each row.

Structural Pests - Organisms that attack and destroy buildings and other structures, clothing, stored food, and manufactured or processed goods. Examples include termites, cockroaches, clothes moths, rats, and dry-rot fungi.

Sub-chronic - Of intermediate duration, usually used to describe studies or periods of exposure lasting between 5 and 90 days.

Sub-chronic Exposure - Multiple or continuous exposures lasting for approximately ten percent of an experimental species' lifetime, usually over a three-month period.

Submerged Aquatic Vegetation (SAV) - Aquatic vegetation, such as sea grasses, that cannot withstand excessive drying and therefore live with their leaves at or below the water surface. SAVs provide an important habitat for young fish and other aquatic organisms.

Sub-registrant - See Distributor.

Sub-surface Drainage - The removal of excess water from the soil profile by means of drain tiles, perforated pipes, or other devices.

Summer Annual - Plant that germinates in the spring or summer and completes its life cycle within one year. Summer annual weeds generally emerge as soon as soil temperatures warm in the spring or early summer. Many species continue to germinate throughout the summer under adequate conditions. Summer annual weeds grow, flower, produce seed, and are killed by frost during the fall season. Summer annual weeds are often difficult to manage, as many species are better suited to summer conditions than desirable cool-season turfgrass species. Examples are crabgrass, knotweed, and prostrate spurge.

Super-chlorination / de-chlorination - The addition of a large dose of chlorine to effect rapid disinfection and chemical reaction in water, followed by reduction of excess free chlorine residual.

Superfund - The program operated under the legislative authority of CERCLA and SARA that funds and carries out EPA solid waste emergency and long-term removal and remedial activities. These activities include establishing the National Priorities List, investigating sites for inclusion on the list, determining their priority, and conducting and/or supervising cleanup and other remedial actions.

Supplemental Distribution - An arrangement whereby a registrant licenses another company to market its pesticide product under the second company's registration.

Supplemental Labeling - EPA-approved written, printed, or graphic material supplied by the pesticide manufacturer that provides additional product information not present on the container label. The additional information may include new application sites and rates, safety guidelines, Worker Protection Standard and PPE requirements, and endangered species advisories.

Surface Drainage - The removal of water that collects on the land surface. A surface drainage system consists of an outlet channel, lateral ditches, and field ditches. Water is carried to the outlet channel by lateral ditches, which receive water from field ditches or from the field surface.

Surface Water - Water that is on the Earth's surface, such as in a stream, river, lake, or reservoir.

Surface Water Treatment Rules (SWTRs) - Drinking water requirements for states and public water systems designed to reduce illnesses caused by pathogens in drinking water. The disease-causing pathogens include Legionella, Giardia lamblia, and Cryptosporidium. The SWTRs requires water systems to filter and disinfect surface water sources. Some water systems are allowed to use disinfection only for surface water sources that meet criteria for water quality and watershed protection.

Surfactant - An inert ingredient that improves the spreading, dispersing, and/or wetting properties of a pesticide mixture.

Susceptible Species - (1) Pest populations that can be controlled by pesticides. (2) Lacking the inherent ability to resist disease or attack by a given pathogen or pest.

Suspended Load - Specific sediment particles maintained in the water column by turbulence and carried with the flow of water.

Suspended Solids - The small solid particles in water that cause turbidity. Particles of suspended sediment tend to settle at the channel bottom, but upward currents in turbulent flow counteract gravitational settling.

Sustainable Agriculture - There is no commonly agreed upon definition of sustainable agriculture. The concept has been, and continues to be, surrounded by controversy. At Washington State University the term is used to describe agricultural management practices that are profitable, environmentally sound and socially acceptable. Broadly speaking, the movement to promote this type of agriculture arose from the negative effects of changes in agriculture that were brought about by vast and rapid technological changes introduced with the application of mechanization and chemicals to farming and ranching.

Swamp - A type of wetland dominated by woody vegetation but without appreciable peat deposits. Swamps may be fresh or salt water and tidal or non-tidal.

Swath - The width of the area covered by one sweep of an airplane, ground sprayer, spreader, or duster.

Symptom - (1) Any detectable change in an organism resulting from the activities of a pathogen or other pest. (2) An indication of pesticide poisoning in humans and other animals.

Synergism (Synergy) - Increased pesticidal activity of a mixture of pesticides above that of the sum of the values of the individual components.

Systemic Effects - Poisoning effects that occur at sites other than the entry point into the body.


Tailings – liquid and solid wastes from mining and milling operations.

Tail Water – The runoff of irrigation water from the lower end of an irrigated field.

Tank Mix/Mixture – Mixture of two or more pesticides in the spray tank at time of application. It is the pesticide user’s responsibility to ensure that all products are registered for the intended use. The user should read and follow the applicable restrictions and limitations and directions for use on all product labels involved in tank mixing. Users must follow the most restrictive directions for use and precautionary statements of each product in the tank mixture.

Target – The plants, animals, structures, areas, or pests to be treated with a pesticide application.

Technical Product - The usual form in which a pesticide is prepared and handled prior to formulation, usually at a high level of purity (95–98%) but not completely pure.

Temperature Inversion – A weather-related event that occurs when cool air is trapped near the surface under a layer of warm air. Under these conditions very little vertical mixing of air occurs. Small spray droplets or vapors may remain suspended in the cool air layer for long periods and move with any airflow. Damage from spray drift often occurs under such conditions.

Teratogen – A substance or agent able to produce abnormalities or defects in living human or animal embryos and fetuses. These defects are not usually inheritable.

Teratogenesis - The introduction of nonhereditary birth defects in a developing fetus by exogenous factors such as physical or chemical agents acting in the womb to interfere with normal embryonic development.

Terrace - (1) A raised, generally horizontal strip of earth and/or rock constructed along a hill on or nearly on a contour to make land suitable for tillage and to prevent accelerated erosion. (2) An earthen embankment, ridge or ridge-and-channel built across a slope (on the contour) to intercept runoff water and reduce soil erosion. Terraces are usually built in a series parallel to one another, with each terrace collecting excess water from the area above. Terraces can be designed to channel excess water into grass waterways or direct it underground to drainage tile and a stable outlet.

Theoretical Maximum Residue Contribution (TMRC) - The theoretical maximum amount of a pesticide in the daily diet of an average person. It assumes that the diet is composed of all food items for which there are tolerance level residues of the pesticide. The TMRC is expressed as milligrams of pesticide/kilograms of body weight/day.

Thermal Stratification – The formation of layers of different temperatures in a lake or reservoir.

Thermocline - Fairly thin zone in a lake that separates an upper warmer zone from a lower colder zone.

Thickener – A drift control adjuvant, such as cellulose or gel, used to promote the formation of a greater proportion of large droplets in a spray mixture.

Threatened Species – Organisms (plants or animals) likely to become endangered.

Threshold - The lowest dose of a chemical at which a specified measurable effect is observed and below which it is not observed.

Threshold Effects Concentration (TEC) – A concentration in media (surface water, sediment, soil) to which a plant or animal is exposed, above which some effect (or response) will be produced and below which it will not.

Threshold Effects Level (TEL) – A chemical concentration in some item (dose) that is ingested by an organism, above which some effect (or response) will be produced and below which it will not. This item is usually food, but can also be soil, sediment, or surface water that is incidentally (accidentally) ingested as well.

Threshold Level - Time-weighted average pollutant concentration values, exposure beyond which is likely to adversely affect human health.

Threshold Limit Value (TLV) - The concentration of an airborne substance that a healthy person can be exposed to for a 40-hour work week without adverse effect; a workplace exposure standard.

Tidal Marsh - Low, flat marshlands traversed by channels and tidal hollows, subject to tidal inundation; normally, the only types of vegetation present are salt-tolerant bushes and grasses.

Tillage - The mechanical manipulation of the soil profile for any purpose. In agriculture it is usually restricted to modifying soil conditions and/or managing crop residues and/or weeds and/or incorporating chemicals for crop production. Various types of equipment are used for tillage, depending on the objective of the tillage. The type and quality of tillage has important environmental impacts. The goal is always optimum pulverization and partial residue coverage because too little or too much will increase run-off. The goal of the final tillage operation (seedbed preparation) is optimum soil particle size reduction to allow close soil contact with the seed while maintaining pores for water and air movement, and a rough surface that dries rapidly and won't germinate weeds. Cultivation is the preferred term after seeding the crop.

  • Chiseling - Breaking up soil using closely spaced gangs of narrow shank-mounted tools. It may be performed at other than the normal plowing depth. Chiseling at depths >40 cm is usually termed subsoiling.
  • Combined Tillage Operations - The simultaneous operation of two or more different types of tillage tools (on the same implement frame) or implements (subsoiler-lister, lister planter, or plow planter) to simplify control or reduce the number of trips over the field.
  • Contour Tillage - Performing the tillage operations and planting on the contour within a given tolerance.
  • Conventional Tillage / Intensive Tillage – Full-width tillage which disturbs all of the soil surface and is performed prior to and/or during planting. It generally involves plowing or intensive (numerous) tillage trips. There is less than 15 percent residue cover after planting, or less than 500 pounds per acre of small grain residue equivalent throughout the critical wind erosion period. Weed control is accomplished with crop protection products and/or row cultivation. Compare to Conservation Tillage.
  • Harrowing - A secondary broadcast tillage operation which pulverizes, smooths, and firms the soil in seedbed preparation, controls weeds, or incorporates material spread on the surface.
  • Plowing – A primary broadcast tillage operation which is performed to shatter soil with partial to complete inversion, usually to depths greater than 20 cm.
  • Primary Tillage - Tillage at any time which constitutes the initial, major soil manipulation operation. It is normally a broadcast operation designed to loosen the soil or reduce soil strength, anchor or bury plant materials and fertilizers, and rearrange aggregates.
  • Reduced Till – Full-width tillage which involving one or more tillage trips which disturbs all of the soil surface and is performed prior to and/or during planting. There is 15-30 percent residue cover after planting or 500 to 1,000 pounds per acre of small grain residue equivalent throughout the critical wind erosion period. Weed control is accomplished with crop protection products and/or row cultivation.
  • Secondary Tillage - Any of a group of separate or distinct tillage operations, following primary tillage, that are designed to provide specific soil conditions for any reason, such as seeding.
  • Subsoiling – Any treatment to fracture and/or shatter soil with narrow tools below the depth of normal tillage without inversion and with a minimum mixing of the soil. This loosening is usually performed by lifting action or other displacement of soil dry enough so that shattering occurs.

Tillage, Conservation - See Conservation Tillage.

Tip-and-Pour – Pesticide container with a built-in measuring device that fills with a given amount of pesticide when the container is tilted.

Tolerance - (1) (a) Herbicide tolerance is the inherent ability of a species to survive and reproduce after herbicide treatment. This implies that there was no selection or genetic manipulation to make the plant tolerant; it is naturally tolerant. (b) Ability to endure infestation (or infection) by a particular pest (or pathogen) without showing severe symptoms of distress. Compare to Resistance. (2) The maximum permissible residue level for pesticides in raw agricultural produce and processed foods. Any food bearing a pesticide residue for which there is no tolerance or exemption from tolerance in effect is considered adulterated and subject to seizure. Similarly, if a pesticide residue in a food exceeds the applicable tolerance, the food would be considered adulterated and subject to seizure. EPA establishes the tolerances, which are enforced by the Food and Drug Administration and the Department of Agriculture. Before the passage of the Food Quality Protection Act of 1996, established tolerances and exemptions for pesticide chemicals in or on RACs were established in section 408 of FFDCA and tolerances, where needed for processed commodities, were set in section 409. Under FQPA, all tolerances or exemptions will be set under section 408. EPA will not register a pesticide under FIFRA until all needed tolerances have been established. See Maximum Residue Level.

Total Dissolved Solids (TDS) - The sum or all inorganic and organic particulate material. TDS is an indicator test used for wastewater analysis and is also a measure of the mineral content of bottled water and groundwater. There is a relationship between TDS and conductivity.

Total Maximum Daily Load (TMDL) - A calculation of the highest amount of a pollutant that a water body can receive and safely meet water quality standards set by the state, territory, or authorized tribe.

Total Suspended Solids (TSS) - A measure of the suspended solids in wastewater, effluent, or water bodies, determined by tests for “total suspended non-filterable solids.” See Suspended Solids.

Toxicity - The degree to which a substance or mixture of substances can harm humans or animals. Acute toxicity involves harmful effects in an organism through a single or short-term exposure. Chronic toxicity is the ability of a substance or mixture of substances to cause harmful effects over an extended period, usually upon repeated or continuous exposure sometimes lasting for the entire life of the exposed organism. Sub-chronic toxicity is the ability of the substance to cause effects for more than one year but less than the lifetime of the exposed organism. See also Dermal Toxicity and Oral Toxicity.

Toxicity Assessment - Characterization of the toxicological properties and effects of a chemical, with special emphasis on establishment of dose-response characteristics. See Dose-Response.

Toxicity Testing - Biological testing (usually with an invertebrate, fish, or small mammal) to determine the adverse effects of a compound or effluent.

Toxicology – The study of the effects of toxic substances on living organisms.

Toxin – A naturally occurring poison produced by plants, animals, or microorganisms. Examples include the poison produced by the black widow spider, the venom produced by snakes, and the botulism toxin.

Transient Non-Community Water System (TNCWS) - A water system which provides water in a place such as a gas station or campground where people do not remain for long periods of time. These systems do not have to test or treat their water for contaminants which pose long-term health risks because fewer than 25 people drink the water over a long period. They still must test their water for microbes and several chemicals.

Translocation – The movement of materials within a plant or animal from the site of entry. A systemic pesticide is translocated.

Trivial Name - Name in general or commonplace usage.

Trophic Level – This term refers to the position of a species (or in some cases, types of species with similar feeding habitats) within a food chain or food web. For example, in a simplified terrestrial (land-based) ecosystem, plants, which produce their own food, are at the lowest trophic level. Above them in the second trophic level, are herbivores such as small rodents, deer, etc. In the third trophic level are carnivores: animals that eat other animals. In scientific terms, an omnivore is an animal that feeds on organisms from different trophic levels, such as a bear which eats fish and berries. In some cases, either due to a lack of complete information or for the sake of simplicity and clarity, instead of specific species, a food web or food chain will have "generic" groups, such as "small insectivorous mammals" or "piscivorous (fish-eating) birds" reported in the different trophic levels.

Turbidity – The cloudy appearance of water caused by the presence of suspended and colloidal matter. Technically, turbidity is an optical property of the water based on the amount of light reflected by suspended particles. In the waterworks field, a turbidity measurement is used to indicate the clarity of water. Turbidity cannot be directly equated to suspended solids because white particles reflect more light than dark-colored particles and many small particles will reflect more light than an equivalent large particle.


Uncertainty Factor (UF) - One of several factors used in calculating the reference dose from experimental data. UFs are intended to account for (1) the variation in sensitivity among humans; (2) the uncertainty in extrapolating animal data to humans; (3) the uncertainty in extrapolating data obtained in a study that covers less than the full life of the exposed animal or human; and (4) the uncertainty in using lowest observed adverse effect level (LOAEL) data rather than no observed adverse effect level (NOAEL) data.

Underground Sources of Drinking Water – Aquifers currently being used as a source of drinking water or those capable of supplying a public water system. They have a total dissolved solids content of 10,000 milligrams per liter or less, and are not "exempted aquifers."

Unreasonable Risk - Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), "unreasonable adverse effects" means any unreasonable risk to man or the environment, taking into account the medical, economic, social, and environmental costs and benefits of any pesticide.

Unsaturated Zone - The area above the water table where soil pores are not fully saturated, although some water may be present.


Vadose Zone - The zone between land surface and the water table within which the moisture content is less than saturation (except in the capillary fringe) and pressure is less than atmospheric. Soil pore space also typically contains air or other gases. The capillary fringe is included in the vadose zone.

Vapor Drift - The movement of chemical vapors from the application site. Like pesticide spray drift, vapor drift can injure non-target plants or animals.

Vapor Pressure - The property that causes a chemical to evaporate. The higher the vapor pressure, the more volatile the chemical—and the more easily it will evaporate.

Variance – A State with primacy may relieve a public water system from a requirement respecting an MCL by granting a variance if certain conditions exist. These are: 1) the system cannot meet the MCL in spite of the application of best available treatment technology, treatment techniques or other means (taking costs into consideration), due to the characteristics of the raw water sources which are reasonably available to the system, and 2) the variance will not result in an unreasonable public health risk. A system may also be granted a variance from a specified treatment technique if it can show that, due to the nature of the system's raw water source, such treatment is not necessary to public health. See Exemption.

Vector – An animal (e.g., insect, nematode, or mite) or plant (e.g., dodder) that can carry and transmit a pathogen from one host to another.

Volatility – The degree to which a substance changes from a liquid or solid state to a gas at ordinary temperatures when exposed to air.

Volatilization – The transfer of a chemical from the liquid to the gas phase. Solubility, molecular weight, vapor pressure of the liquid, and the nature of the air-liquid interface affect the rate of volatilization. See also Pesticide Volatilization.


Water and Sediment Control Basin (WASCOB) - A small earthen ridge and channel or embankment built across (perpendicular to) a small watercourse or area of concentrated flow within a field. They are commonly built in a parallel series with the first ridge crossing the top of the watercourse and the last ridge crossing the bottom, or nearly so. They are designed to trap agricultural runoff water and sediment as it flows down the watercourse; this keeps the watercourse from becoming a field gully and reduces the amount of runoff and sediment leaving the field. They are similar to terraces in form and function but are generally reserved for fields with irregular topography where contour practices would be difficult to implement or likely to fail.

Waterproof - As specified by the pesticide product label, PPE that is “made of material that allows no measurable movement of water or aqueous solutions through the material during use” [U.S. EPA. 40 CFR 170.240 Personal protective equipment].

Water Quality - The chemical, physical, biological, radiological, and thermal condition of water.

Water Quality Criteria - Scientifically derived ambient limits developed and updated by EPA, under section 304(a)(1) of the Clean Water Act, for specific pollutants of concern. Criteria are recommended concentrations, levels, or narrative statements that should not be exceeded in a waterbody in order to protect aquatic life or human health.

Water Quality Standards - Laws or regulations, promulgated under Section 303 of the Clean Water Act, that consist of the designated use or uses of a water body or a segment of a water body and the water quality criteria that are necessary to protect the use or uses of that particular water body. Water quality standards also contain an anti-degradation statement. Every State is required to develop water quality criteria standards applicable to the various waterbodies within the State and revise them every 3 years.

Watershed - Land area from which water drains toward a common watercourse in a natural basin.

Watershed Approach - A coordinated framework for environmental management that focuses public and private efforts on the highest priority problems within hydrologically defined geographic areas.

Watershed Management - Water resource protection, enhancement, and restoration. Ideally, watershed management means developing a solution for each watershed that considers all its problems, includes all stakeholders in defining the problems, proposing solutions, and participating in implementing a common solution.

Water Table - Level below the earth's surface at which the ground becomes saturated with water. The surface of an unconfined aquifer which fluctuates due to seasonal precipitation.

Water Treatment Lagoon - An impound for liquid wastes, so designed as to accomplish some degree of biochemical treatment of the wastes.

Waterway - Any channel, natural or constructed, in which water flows.

Weed - A plant growing where it is not wanted or where it is in direct conflict with the well-being of humans and their activities.

Weir - A wall or plate placed in an open channel to measure the flow of water; a wall or obstruction used to control flow from settling tanks and clarifiers to ensure a uniform flow rate and avoid short-circuiting.

Well (Water) - an artificial excavation put down by any method for the purposes of withdrawing water from the underground aquifers. A bored, drilled, or driven shaft, or a dug hole whose depth is greater than the largest surface dimension and whose purpose is to reach underground water supplies or oil, or to store or bury fluids below ground.

Well Field - Area containing one or more wells that produce usable amounts of water.

Wellhead Protection - The practice of preventing pollutants from seeping into well water at or near any active or abandoned well.

Wellhead Protection Area - A protected surface and subsurface zone surrounding a well or well field supplying a public water system to keep contaminants from reaching the well water.

Wetland - An area that is saturated by surface water or ground water with vegetation adapted for life under those soil conditions, as in swamps, bogs, fens, marshes, and estuaries.

Wetting Agent - An adjuvant used to reduce the surface tension between a liquid and the contact surface for more thorough coverage.

Winter Annual - A plant that starts germination in the fall, lives over winter, and completes its growth, including seed production, the following season. Winter annuals germinate from seed in the late summer or early fall. Young winter annual plants live through the winter then flower, set seed, and die out the following summer. Winter annuals generally cannot survive the hot summer months. Occasionally, winter annuals will germinate in the spring, but even spring-germinating weeds die out the following summer. Some examples of winter annuals are shepherd's purse, common chickweed, yellow rocket, and annual bluegrass.

Worker Protection Standard (WPS) - A federal regulation that is meant to reduce the risk of pesticide poisoning and injuries among agricultural workers and handlers. The WPS requires agricultural employers to provide protections to workers and handlers, including but not limited to safety training, posting of application sites, and decontamination supplies.


Zero Tolerance - Indicates that no detectable amount of a specified pesticide or other contaminant (such as glass, metal, or plastic) may remain on the raw agricultural commodity when it is sold or utilized.

View list of sources and additional links for important agriculture-related terms.

Below is a list of sources and additional links for important agriculture-related terms.

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