Assessment of entomopathogenic fungi for endophytism in corn and as a mortality factor for western corn rootworm larvae

Western corn rootworm, Diabrotica virgifera virgifera (LeCont) (Coleoptera: Chrysomelidae), is a serious pest of corn. Corn rootworm larvae reside in the soil and feed on corn roots, which in turn reduces yield. Because western corn rootworm has developed resistance to several management techniques, such as crop rotation and transgenic corn, new approaches to manage this pest would be of value. Entomopathogenic fungi (EPF) such as Beauveria spp. and Metarhizium spp. naturally occur in soil and have been used for pest management in other systems. The natural occurrence of entomopathogenic fungi in the soil and evidence of endophytic and rhizospheric competencies raises the possibility that these species may be useful for managing corn rootworm larvae. We studied the effects of Beauveria bassiana (GHA) and field-collected isolates of Beauveria and Metarhizium on the mortality of western corn rootworm larvae. Western corn rootworm larval mortality from Beauveria and Metarhizium isolates was assessed in both sterile and soil-based bioassays. Additionally, corn seeds were inoculated with B. bassiana, and plants were evaluated for endophytism by B. bassiana and the persistence of B. bassiana in the rhizosphere. Results from these studies will provide a better understanding of interactions among corn, corn rootworm, and EPF, and cast light on the potential for EPF to be used in the management of rootworm.