New varieties of Bt corn are being developed to control corn rootworm pests. Movement rates of adults between Bt and refuge fields of the target insect are key parameters for designing a effective insect resistance management (IRM) plan. We modified a method originally developed by Dempster to estimate movement rates of adult northern corn rootworm, Diabrotica barberi Smith and Lawrence, and adult male and female western corn rootworm, D. virgifera virgifera LeConte. Continuous corn fields (planted to corn for two consecutive years) were identified as source fields, and first year corn fields (rotated into corn from a different crop the previous year) were destination fields. Destination fields were chosen at varying distances from source fields, and rootworm populations in these fields were assumed to have emigrated from source fields. Population densities were counted at nine points in each field. Samples were taken by visual counts of corn rootworms on plants in early morning when flight activity was low. The data were analyzed to calculate the diffusivity of each type of corn rootworm. Results from 2001 indicate female western corn rootworm had the highest diffusivity (382 ± 119 m2/day), and male western corn rootworm and northern corn rootworm adults had diffusivities that were similar (140 ± 18 and 103 ± 16 m2/day, respectively). These movement rates can be used to facilitate modeling the characteristics of Bt corn fields and refuges to delay corn rootworms evolving resistance to Cry toxins.
Species 1: Coleoptera Chrysomelidae Diabrotica barberi (northern corn rootworm)
Species 2: Coleoptera Chrysomelidae Diabrotica virgifera virgifera (western corn rootworm)
Keywords: corn rootworm, movement
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