A variant of the western corn rootworm (WCR, Diabriotica virgifera virgifera LeConte) that lays eggs in soybeans has caused significant damage when a corn-soybean rotation is practiced. We previously determined that advancing corn phenology increases WCR acceptance of soybeans for feeding. Given that corn phenology influences WCR movement within cornfields, we suggest that WCR response to advancing corn phenology may also result in dispersal from corn. In landscapes dominated by a corn-soybean rotation, subsequent movement to and oviposition in soybean fields would increase survival. To test this model, we designed a no-choice assay to characterize WCR dispersal from corn leaves or tassels. The influence of corn phenology on WCR dispersal was evaluated with corn leaves from two unique growth stages (vegetative and reproductive stages) and a sham leaf control. We used WCR from a lab colony reared within a single cohort. We counted the number of WCR that remained on the treatment leaf and the surface area eaten during 24 hr. We observed greater dispersal from reproductive stage corn leaves than the sham (chi-square=15.69, df=1, P=0.001) and from vegetative stage corn leaves than the sham (chi-square=21.17, df=1, P=0.001). Though nearly twice as much leaf area was eaten from vegetative than reproductive corn leaves and fewer WCR remained on reproductive corn after 24 hr, there was not a significant difference in beetle retention between the two stages (chi-square=0.66, df=1, P=0.41). However, there were more WCR (chi-square=11.64, df=1, P=0.001) retained on tassels shedding pollen (VT-R1 stage) than those no longer producing pollen (R2 stage). Future research will investigate if variant WCR differ in their response to corn phenology and if nutritional status affects WCR dispersal.
Species 1: Coleoptera Chrysomelidae Diabrotica virgifera (western corn rootworm)
Keywords: dispersal, corn
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA