Assessing corn rootworm (CRW) beetle pressure is an important part of assembling a management plan. Here are six ways to make the most of monitoring.
1. Start with the Right Trap
- Use yellow sticky traps that are about 6” x 12” with grids to make counting quicker
- Look for non-pheromone traps with a hanging mechanism
- Ensure traps are sturdy enough to withstand wind
2. Placement Matters
- Install traps at ear height and space them evenly throughout the field
- Use a minimum 12 traps per field
- Space traps out across field as much as possible
- Place traps at least 100 feet from field edges
- Avoid placing traps near waterways or field boundaries
3. Timing Is Key
- Begin monitoring when first beetles emerge (usually early-mid July)
- Continue monitoring for 6-8 weeks
- Record dates and beetle counts consistently
- Do not stop monitoring until trap numbers begin to decline
4. Maintain Your Traps
- Replace traps weekly regardless of condition
- Remove debris that could reduce trap effectiveness
- Check for damage from weather/equipment
- Store unused traps properly
5. Document the Results
- Record counts by species (Western vs. Northern)
- Note weather conditions
- Track field history and rotation
- Document patterns in adjacent fields
- Map trap locations for future reference
6. Put the Results To Work
- Use established economic thresholds to guide management decisions
- Western CRW: 2 beetles/trap/day
- Northern CRW: 1.5 beetles/trap/day
- Calculate weekly averages
- Consider historical pressure