Western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), resistant to crop rotation frequently move between corn, Zea mays L., and soybean, Glycine max L. Merril, fields, laying eggs in both crops. By comparing the behavioral and reproductive responses of beetles experiencing mixed corn and soybean diets to those provided with a continuous corn diet, the cost of mixing diets was measured. Larvae were collected near Urbana, IL (rotation-resistant population) and Monmouth, IL (rotation susceptible population) and reared to adults in the laboratory. Females from each population were assigned to alternating corn and soybean diets of different durations. Beetles were more likely to feed on corn if it followed soybean than if they had continuous access to corn. The cost of moving between corn and soybean are minimal; the fecundity of beetles given alternating diets of corn and soybean was similar to that of beetles given daily access to corn diets. Beetles laid more eggs on days when they had access to soybean than on days with corn, suggesting dietary stress can induce oviposition. The only behavioral difference detectable between the two populations was a difference of activity in response to soybean. We found no evidence that rotation-resistant adult D. v. virgifera have been selected to preferentially feed or oviposit in soybean. Instead, D. v. virgifera we hypothesize that periods of exposure to a non-host plant results in nutritional stress that induces oviposition, lowers the threshold for feeding, and increases beetle activity.
Species 1: Coleoptera Chrysomelidae Diabrotica virgifera (western corn rootworm)
Keywords: crop rotation, diet-mixing
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