Behavioral and Feeding Assays Reveal a Western Corn Rootworm (Coleoptera: Chrysomelidae) Variant That is Attracted to Soybean

Abstract

Economic injury by western corn rootworm, Diabrotica virgifera virgifera Le-Conte, larvae to corn grown in rotation with soybean has been increasing in areas of northwestern Indiana and east central Illinois. To ascertain whether behavioral changes in adults are resulting in larval damage to corn in these areas, the attractiveness of soybean, corn, and associated cropping environments to western corn rootworm beetles from Indiana, Iowa, and Nebraska was compared using laboratory assays. In a 6-choice host preference assay, beetles from Indiana preferred soybean without crop residue and pollinated corn more than water wicks, corn residue, pollinating corn, or soybean with corn residue. Beetles from Nebraska favored pollinating and pollinated corn. Western corn rootworm beetles from Indiana selected soybean without residue more than beetles from either Iowa or Nebraska. In a no-choice feeding assay, beetles from Indiana consumed a greater amount of soybean leaf area than did beetles from either Iowa or Nebraska. Results were obtained using laboratory assays and thus may not always be applicable to the field. However. findings indicated that a western corn rootworm variant may be present in a portion of the population in northwestern Indiana. This variant preferred soybean environments over corn environments. Risk of economic injury to corn planted after soybean may be greater where this variant is prevalent.