Iowa farmer perception of corn rootworm resistance
click image to zoomFigure 4. Percent of respondents who suspected a corn rootworm trait failure in at least one of their cornfields in 2012. To understand where most of the perceived Bt trait failures were occurring within Iowa, we grouped responses by region. About one-third of people in northeast Iowa suspected a Bt trait failure in 2012 (Figure 4). Most of the positive verifications were in north central Iowa, with approximately one-third of people reporting Bt trait failures (Figure 5).
click image to zoomFigure 5. Percent of respondents who positively verified corn rootworm trait failure. If you find injury to Bt corn on more than one node, consider diversifying pest management for that field. Severe injury may be due to western corn rootworm that has developed Bt resistance, and resistance should be suspected in these cases. The Department of Entomology at Iowa State University is working to understand the extent of resistance within the state and to develop management recommendations for Bt-resistant populations of western corn rootworm. Please contact Aaron Gassmann or Erin Hodgson to report fields with suspected resistance.