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Western corn rootworm, Diabrotica virgifera virgifera LeConte, biology is tied to the continuous availability of its host (corn, Zea mays L.). Annual rotation of corn with a nonhost, like soybean (Glycine max (L.) Merrill) was a reliable tactic to manage western corn rootworm. Behavioral resistance to annual crop rotation (rotation resistance) allowed some eastern U.S. Corn Belt populations to circumvent rotation by laying eggs in soybean and in cornfields. When active in soybean, rotation-resistant adults commonly consume foliage, in spite of detrimental effects on beetle survival. Rotation-resistant beetle activity in soybean is enabled by the expression of certain proteinases and an adapted gut microbiota that provide limited protection from soybean antiherbivore defenses. We investigated the effects of corn and soybean herbivory on rotation-resistant female survival and initiation of flight using mortality assays and wind tunnel flight tests. Among field-collected females tested with mortality assays, beetles from collection sites in a cornfield survived longer than those from collection sites in a soybean field. However, reduced survival due to soybean herbivory could be restored by consuming corn tissues. Field-collected beetles that fed on a soybean tissue laboratory diet or only water were more likely to fly in a wind tunnel than corn-feeding beetles. Regardless of collection site and laboratory diet, 90.5% of beetles that flew oriented their flights upwind. Diet-related changes in the probability of flight provide a proximate mechanism for interfield movement that facilitates restorative feeding and the survival of females previously engaged in soybean herbivory. [ABSTRACT FROM AUTHOR]

Western corn rootworms, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), with resistance to crop rotation, frequently move between fields of corn, Zea mays L., and soybean, Glycine max L. Merril, 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 (typical 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 a mixed corn and soybean diet was minimal; the fecundity of females given alternating diets of corn and soybean was similar to that of beetles given daily access to corn diets. Females laid more eggs on days when they had access to soybean than on days with access to corn, suggesting dietary stress can induce oviposition. The only behavioral difference between the populations was a greater sensitivity to daily alternation of corn and soybean diets among beetles from the rotation-susceptible population. We found no evidence that rotation-resistant adult D. v. virgifera have any greater inclination or capacity to feed on soybean tissue than rotation-susceptible adults. Instead, periodic exposure to soybean results in nutritional stress that increases oviposition rate, lowers the threshold for feeding, and increases beetle activity. [ABSTRACT FROM AUTHOR]

The role of soybean, Glycine max (L.) Merril (Fabaceae), in the circumvention of crop rotation was evaluated by observing the effects of soybean herbivory on western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) survival and oviposition. Field collected D. virgifera adults resistant to annual rotation of corn, Zea mays (L.) (Poaceae), and soybean were given the opportunity to feed on a soybean pre-treatment diet prior to diet combinations of corn, soybean, and/or water. The number of days that the adults survived after removal of the diet combinations was used as a measure of insect vigor and diet quality. Willingness to feed on a soybean foliage pre-treatment did not indicate greater ability to benefit nutritionally from soybean herbivory. Adult D. virgifera previously feeding on corn, soybean, or water survived starvation for 8.3 ± 0.15 days, 5.1 ± 0.13 days, and 3.9 ± 0.14 days, respectively. Diabrotica virgifera recover from 2 days of starvation or poor diet if subsequently given access to corn tissues for 2 days. Eggs were laid within 1 day of access to poor diet or starvation. Other D. virgifera, captured as they flew from a cornfield into a soybean field, were maintained on soybean foliage or only water until they died. Of the beetles with access to soybean foliage, 24% fed within 24 h after capture and survived 1 day longer than insects given only water. Only 20% of these D. virgifera were able to lay eggs without consuming additional corn prior to death. Few D. virgifera enter soybean fields capable of immediate oviposition. Female reproductive status and diet quality influence the likelihood of oviposition following exposure to stress. The effects of soybean herbivory may contribute to the proximate mechanism of resistance to crop rotation. [ABSTRACT FROM AUTHOR]