Pest Control · July 2025 · 5 min read
Corn rootworm is the most economically damaging corn pest in the United States, costing growers billions annually in yield losses and control expenses. Effective prevention starts with understanding species behavior and combining cultural and chemical strategies.
The western and northern corn rootworm are the primary species affecting U.S. corn production. Adults lay eggs in corn fields during late summer, and larvae hatch the following spring to feed on corn roots. Western corn rootworm variants have developed extended diapause and rotation-resistant egg-laying behavior, making management more complex.
Bt hybrids expressing Cry3Bb1, Cry34/35Ab1, or mCry3A proteins provide rootworm larval control but should be rotated among trait families annually. Crop rotation to soybeans or other non-host crops remains the most reliable cultural control, breaking the larval feeding cycle. In areas with rotation-resistant western corn rootworm, adult scouting and soil insecticides supplement rotation.
Planting the same Bt trait year after year in continuous corn has driven field-evolved resistance in multiple states. Use integrated pest management by rotating traits, incorporating soil-applied insecticides like tefluthrin or bifenthrin in high-pressure fields, and planting structured refuges. Monitor root damage ratings annually — a score above 0.5 on the Iowa State node-injury scale warrants a management change.
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