Farm Progress released on May 11 a guide outlining four key steps to improve corn rootworm management for farmers. The publication recommends annual checks for corn rootworm feeding and potential root injury in all cornfields, including both non-Bt and Bt-traited hybrids, to help determine if management strategies should be adjusted the following year.
Corn rootworm can cause significant damage to crops, impacting yields and farm profitability. Effective monitoring and timely intervention are crucial for managing this pest. According to Farm Progress, the optimum period for scouting is from mid-July through mid-August, with particular attention given to continuous cornfields or those showing Bt performance issues. Fields following soybeans should also be evaluated as a precaution against future concerns.
The article highlights that western corn rootworm variants in Iowa can overcome crop rotation by laying eggs outside of cornfields, while northern variants use extended diapause—delaying egg hatching by two or three years. “It’s important to note that northern CRW does not lay eggs outside of cornfields,” the article says.
Farmers are advised first to track egg hatch using growing degree days; research indicates that half of egg hatch occurs between 684 and 767 accumulated degree days (base 52°F soil). Corn rootworm egg hatch in Iowa typically peaks around June 6 in central regions. Resources such as the Iowa Environmental Mesonet and the Iowa Pest Alert Network provide updates on local conditions.
Second, examining roots for injury about two weeks after peak hatch is recommended. Using a zero-to-three node-injury scale developed by Iowa State University entomologists helps assess larval damage; every node lost can reduce yield by up to 17%. Ratings above specific thresholds indicate unacceptable injury levels according to U.S. Environmental Protection Agency standards.
Third, farmers can confirm larvae presence with a float test: placing uprooted plants with soil into water will cause larvae near roots to float up. Fourth, monitoring adult beetle populations using sticky traps provides additional data on pest activity across Iowa through networks coordinated by ISU Extension specialists.
Summing up their recommendations, Farm Progress states: “Farmers should adjust their management approaches to keep larval feeding injury below the economic injury level.” The group notes that greater-than-expected injuries may suggest resistance but require laboratory confirmation.
According to the official website, Farm Progress supports agricultural communities with market updates and educational programs as part of Informa PLC’s Informa Markets Division. The organization distributes content via regional publications and digital platforms under eighteen brands nationwide and organizes events such as the Farm Progress Show and Husker Harvest Days.
