Northern corn rootworm
- Adult: Small bug; color varies from cream to pale green.
- Larvae: Slender, about ½" long and white with a brown head and dark spot on the posterior end.
- Eggs: White, football-shaped and very tiny.
Timing of damage: V8 to R5
Type of damage: Larvae feed on and tunnel into roots. Adults feed on and clip corn silks.
Scouting: For larvae, dig up 10 randomly chosen plants and check soil for rootworms. For adults,
count the number of beetles on five plants each in five separate locations.
Economic threshold: For larvae, treat if two or more are found per plant. For adults, treat if silks are clipped to ½" or less before 50% of plants have been pollinated when beetles are present.