|Ellsbury, Michael - RETIRED ARS|
Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 11, 2008
Publication Date: April 20, 2009
Citation: Lundgren, J.G., Nichols, S.J., Prischmann, D.A., Ellsbury, M. 2009. Seasonal and Diel Activity Patterns of Generalist Predators Associated with Diabrotica Virgifera Immatures (Coleoptera: Chrysomelidae). BioControl Science and Technology. 19(3):327-333. Interpretive Summary: Western corn rootworm (Diabrotica virgifera) is a serious pest of corn in North America and Europe. Little is known of the predators that help to reduce the egg and larval populations of this pest. We used degree day models to predict the occurrence of egg and larval populations of rootworms, and time-sorting pitfall traps to monitor the activity patterns of predators over the pest’s life cycle and over the 24-hour diel cycle. A diverse and abundant predator community overlapped with rootworms, including harvestmen, rove beetles, spiders, and carabid beetles. Major results were that 1) the egg stage of the pest overlaps with more predators than the larval stage, 2) the predator community changes dramatically over the life cycle of the pest, and 3) predators are easily categorized as day- and night-active species. These results are a first step in developing conservation biological control programs for the rootworm
Technical Abstract: Diabrotica virgifera is one of the worst pests of agriculture worldwide, but little is known of the predator community associated with the soil-dwelling immature stages of the pest. This study describes the epigeal generalist predator community associated with the egg stage and 1st-3rd stadia of D. virgifera. Time-sorting pitfall traps were employed to determine the diel activity patterns of main predator groups (operational taxonomic units; OTU). Seventeen predominant OTUs were captured concurrently with the immature stages of D. virgifera, including carabids, staphylinids, spiders, harvestmen, crickets, and mites. The egg stage is substantially longer than the larval stages, and is exposed to more predator OTUs. Predators (except Gryllus pennsylvanicus) were easily categorized as day- (n = 7 OTUs) and night- (n = 4 OTUs) active guilds; the remaining 5 OTUs were composites of multiple species and as such their activity patterns were not easily defined. An abundant and diverse epigeal predator community is associated with D. virgifera immatures, and seasonal and diel partitioning of the season may contribute to the maintenance of this community structure within cornfields.