Oviposition behaviors in relation to rotation resistance in the western corn rootworm.

ABSTRACT

Across a large area of the midwestern United States Corn Belt, the western corn rootworm beetle (Diabrotica virgifera virgifera LeConte, Coleoptera Chrysomelidae) exhibits behavioral resistance to annual crop rotation. Resistant females exhibit increased locomotor activity and frequently lay eggs in soybean (Glycine max L.) fields, although they also lay eggs in fields of corn (Zea mays L.) and other locations. The goals of this study were (1) to determine whether there were any differences in ovipositional behavior and response to plant cues between individual rotation-resistant and wild-type females in the laboratory and (2) to examine the roles of, and interaction between, host volatiles, diet, and locomotor behavior as they related to oviposition. Because rootworm females lay eggs in the soil, we also examined the influence of host plant roots on behavior. In the first year of the study, rotation-resistant beetles were significantly more likely to lay eggs in the presence of soybean foliage and to feed on soybean leaf discs than wild-type females, but this difference was not observed in the second year. Oviposition by rotation-resistant females was increased in the presence of soybean roots, but soybean herbivory did not affect ovipositional choice. Conversely, ovipositional choice of wild-type females was not affected by the presence or identity of host plant roots encountered, and wild-type females consuming soybean foliage were more likely to lay eggs.