Development of an artificial diet for the western corn rootworm

The Western Corn Rootworm, Diabrotica virgifera (WCR; Coleoptera: Chrysomelidae), is a serious pest of maize, causing approximately one billion dollars a year in losses and control costs. The insect has become resistant to several chemical controls and growers have asked for a control solution based on genetically-enhanced resistant varieties. Key to the production of genetically-enhanced germ plasm is the ability to use artificial diets for bioassays to identify proteins with activity against the target insect. However, artificial diets currently used for WCR bioassay do not support good WCR larval development because they were developed and optimized for the Southern Corn Rootworm (SCR). The present study was conducted to understand the nutritional physiology of WCR by altering the dietary constituents of a SCR diet and measuring the subsequent effects on WCR growth. Alteration of most dietary constituents had surprisingly little effect on WCR larval growth. The most significant factors affecting WCR growth on artificial diet were removal of formalin, addition of plant adjuvant, and adjustment of dietary pH to 9.0. These dietary changes resulted in larval WCR growth rates that were nearly double those in standard SCR rootworm diets. In some cases, WCR larvae fed on the improved diet obtained larval masses approaching those of larvae fed on maize roots.