Corn Earworm Management Guidelines
New Corn Earworm Dynamic Management Tool
In 2024 and 2025, commercial farmers saw extensive injury to sweet corn ears. In 2024, two Iowa fields had 57% and 100% pyrethroid (Group 3A) resistant corn earworm. Assays from 2025 collections are pending.
Resistance issues prompt questions about profitable and sustainable solutions to manage CEW. We developed a dynamic tool to help farmers implement integrated pest management (IPM) practices and use decision-making tools to improve their return on investment (ROI).
Read our 2026 poster
We presented a poster for the 2026 Northcentral Branch of the Entomological Society of America Meeting in Des Moines. The poster highlights three management scenarios to manage corn earworm in sweet corn.
Corn Earworm Management Plan in Sweet Corn
Monitor moth flights
Corn earworms migrate to Iowa every year. The peak activity and intensity can be variable between fields and growing seasons. Using pheromone-baited traps to monitor for adults will help understand local activity and risk. For best results, invest in a mesh Heliothis trap (right) and replace lures every 2-3 weeks.
Spray effective foliar insecticides based on thresholds
Alternate insecticide group numbers to prolong the effectiveness of labeled products. Avoid pyrethroids (Group 3A) if possible due to poor performance.
Use effective Bt seed genetics
Use Bt hybrids, if they are acceptable to consumers, for late-season plantings. Consider sweet corn hybrids with the Attribute II or Attribute Plus trait packages since Vip3A is the only Bt protein without widespread documented resistance for corn earworm.
Recommended Insecticides
The brands listed are not all-inclusive, but are meant to provide examples of products for sweet corn in Iowa. Always check the label before you apply pesticides. Review the application guidelines, safety information, personal protective equipment, and pre-harvest intervals.