Scouting for Corn Rootworm Beetles with Sticky Traps

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Estimating Corn Rootworm Populations

Counting corn rootworms in the summer allows growers to make better informed decisions regarding management options the following season.
Pioneer and university research has shown that yellow sticky traps are an easy, convenient, and reliable method for estimating corn rootworm populations within a cornfield.

Use Yellow Sticky Traps

PHEROCON® AM/NB traps* (no bait) are the preferred product for trapping corn rootworm beetles.
Trapping should begin at the blister stage (R2) after silking.
Count the beetles on each trap at 7-day intervals.
- If the count averages more than 50 beetles, no more trapping is needed.
- If the beetle count is below a 50 beetle per trap average, place new traps in the field and continue another 7 days.
- Continue trapping for 4 weeks, or until traps average >50 beetles per trap, whichever comes first.

Trap Placement

Place 6 traps per field, arranged down 1 row and the length of the field.
Traps should be at least 100 feet from the field edge; beetle populations at field edges may not accurately represent the overall field population.
- Attach the trap to the stalk directly above the ear.
- Fold the trap with the sticky side out around the stalk and fasten using a twist tie; lock the trap tab in the lower corner of the trap.
- Remove nearby leaves that may get caught on the trap.
- Mark the row where the traps are located.

Action Thresholds

Contact your local Pioneer sales professional for best management practices for corn rootworm.

Traps average fewer than 21 beetles per trap per week.

Low rootworm populations anticipated next year.
Select an option for low populations:
- Rotate to another crop.
- Plant non-Bt rootworm product with P1250.
- Plant non-Bt rootworm product with soil insecticide.
- Plant corn rootworm Bt corn product.

Traps average 21-50 beetles per trap per week.

Moderate rootworm populations anticipated next year.
Select a control option for moderate populations:
- Rotate to another crop.
- Plant corn rootworm Bt corn product.
- Apply soil insecticide at planting for larvae.
- Apply foliar insecticide in the current year to control adult beetles prior to egg-laying.

Traps average >50 beetles per trap per week.

High rootworm populations anticipated next year.
Select a control option for high populations:
- Rotate to another crop (best for soybean variant beetles or extended diapause beetles.)
- Apply foliar insecticide in the current year to control adult beetles prior to egg-laying and use a rootworm resistant Bt corn or soil-applied insecticide the following year.
- Plant corn rootworm Bt corn product and consider adding a soil-applied insecticide.
- Use a pyramided corn rootworm Bt product; if in Cry3Bb1 or mCry3A problem areas, consider adding a soil-applied insecticide.

Corn Rootworm Beetle Identification

The western corn rootworm has 3 stripes, or 1 broad stripe, on the wing covers. The legs are partially black, but not banded.
The northern corn rootworm lacks stripes or spots on the wing covers. It is solid green, tan, or light yellow in coloration.