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Take Control of Tar Spot in Corn

Tar Spot is a relatively new fungal disease facing corn growers in the Midwest.

What is Tar Spot?

From 2018 - 2023, Tar Spot cost U.S. corn
farmers $3 billion.1

Tar Spot can affect corn yield by
up to 60 bushels per acre.

A latency period of up to 14 days
makes it a challenge to control.

Spotting Tar Spot in Corn

  • Tar Spot has been reported in Florida, Georgia, Illinois, Indiana, Iowa, Kentucky, Michigan, Missouri, Nebraska, New York, Pennsylvania and Wisconsin.
  • Spread by wind and machinery, Tar Spot reduces the plant’s ability to take in sunlight.
  • Tar Spot lesions are black spots that have a raised, bumpy texture and do not rub off.
  • The disease begins on the lower leaves and then moves to the upper plant and ear husks.

Controlling Tar Spot

Controlling Tar Spot in corn requires a multifaceted approach.

Select NK hybrids
Apply fungicides
Rotate crops and incorporate tillage

Select the Right NK Corn Hybrid

NK9771-DV

Tremendous Adaptation Across Soil Types Leads to Excellent Yield Potential

  • Proven disease package
  • Great choice for variable and drought-prone soils
  • Very good emergence and excellent vigor allow for early planting

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NK9908-AA    NEW

Shorter Hybrid with Outstanding Yield Potential and Very Good Test Weight

  • Incredible emergence and vigor allow for planting into tough conditions
  • Very strong roots combined with dependable stalks enables season-long standability
  • Strong performance potential in moderate to well drained soils

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NK0123-AA

Excellent Yield Potential and Exceptional Versatility Across Soil Types

  • Very strong emergence and great seedling vigor
  • Superb roots and strong stalks are a consistent strength of this product
  • Above-average drought tolerance delivers dependable results

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NK0252-D

Exceptional Yield Potential and Tremendous Adaptation Across Soil Types

  • Strong choice for first planting with excellent emergence and seedling vigor
  • Outstanding roots and dependable stalks for late-season standability
  • This product delivers dependable performance across variable environments

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NK0415-AA    NEW

Exciting Genetics with a Distinguishing Ear Type and Grain Quality

  • Taller plant type with solid roots and stalks for season-long standability
  • Dependable Goss’s Wilt and Tar Spot tolerance for high disease pressure acres
  • Outstanding emergence with very good early season vigor allows for early planting

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NK0880 - V

Widely Adapted Hybrid Across Soil Types with Very Strong Drought Tolerance

  • Dependable emergence with strong seedling vigor for a quick start
  • Robust plant type supported by superb roots
  • Excellent Tar Spot and Anthracnose Stalk Rot tolerance

View Product Details

To find the right NK corn hybrid for your fields, contact your local retailer.

Find Your Retailer

Apply Fungicide When Needed

  • Early fungicide applications, at or before the first signs of development, have been effective against Tar Spot.
  • If conditions are favorable for Tar Spot development early in the season, consider a two-pass fungicide program.
  • Be sure to use multiple active ingredients.

Consider Crop Rotation and Tillage

  • Rotating to crops other than corn and using tillage to bury residue can help reduce fungus inoculum levels.

Be proactive & get the right seed to manage tar spot

Find the right fit

Tar Spot FAQs

What is Tar Spot in corn?

Tar Spot in corn is a new and emerging fungal disease in the Midwestern U.S. caused by Phyllachora maydis. This is not the same disease that affects maple trees, which is caused by Rhytisma acerinum.

Is Tar Spot a fungus?

Yes, it is a fungal disease of corn that infects and damages the upper and lower leaf surfaces of the plant. When severe, it can appear on husks and leaf sheaths as well.

What does Tar Spot look like?

Tar Spot can be identified on corn leaves by small, raised black circular spots that resemble tar and do not rub off. But in most cases, the plant is infected long before symptoms are visible.

How does Tar Spot affect corn yield?

According to the Crop Protection Network , yield losses due to tar spot can be variable, depending on the time of disease onset, weather conditions and hybrid susceptibility. In severe cases, losses of 50 bushels per acre or more have been observed on susceptible hybrids.

Yield losses are a function of reduced ear weight, poor kernel fill and vivparity (a condition in which the seed germinates while still on the cob).

Stalk rot and lodging may increase when Tar Spot severity is high. Severe Tar Spot also reduces silage corn feed quality by reducing moisture, decreasing digestible components and reducing energy. No associated mycotoxins have been reported for this disease.

How is Tar Spot spread?

Tar Spot is spread by wind-driven rain and storms, plant residue, and machinery.

Does Tar Spot overwinter?

Yes, it overwinters in soil and residue and thrives in cool (60-70 degrees Fahrenheit) and humid conditions with prolonged periods of wet leaves.

How fast does Tar Spot spread?

Tar Spot can infest, form spores and reinfect in approximately 21 days.

How do I manage Tar Spot of corn?

  • Select hybrids with resistance to Tar Spot.
  • Consider applying fungicides.
  • Manage irrigation.
  • Rotate to other crops.
  • Manage residue.
  • Scout for Tar Spot.

Is corn Tar Spot harmful to humans?

To date, there is no evidence to indicate that Tar Spot in corn produces harmful mycotoxins.

What is the best fungicide for Tar Spot?

If conditions are favorable for Tar Spot development early in the season, consider a twopass fungicide program using Trivapro® or Miravis® Neo fungicide at the V4-V8 corn growth stage and the VT/R1 growth stage.

If the risk of Tar Spot is lower, consider an application of Trivapro or Miravis Neo fungicide at the VT/R1 growth stage, which may also combat other yield-reducing corn foliar diseases.

1 https://cropprotectionnetwork.org/publications/corn-disease-loss-estimates-from-the-united-states-and-ontario-canada-2024#:~:text=Tar%20spot%20caused%20the%20greatest,with%20280%20million%20bushels%20lost

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