Comparison of the efficacy of Beauveria bassiana GHA to field collected isolates in sterile and soil-based assays

Western corn rootworm, Dibrotica virgifera virgifera (LeConte) (Coleoptera: Chrysomelidae), a major pest of corn, causes root injury and economic damage in its larval stage. Some populations of western corn rootworm have developed resistance to traditional methods of management, such as the use of transgenic traits and crop rotation. This resistance creates a need for a broader suite of management tools to reduce the reliance on traditional methods. One such tool includes entomopathogenic fungi (EPF), such as Beauveria bassiana (Hypocreales: Cordycipitaceae), which are ubiquitous in agricultural field soil. While EPF are used as biopesticides for pest management in greenhouse settings, widespread use of EPF for field crops such as corn has not been adopted. This study focuses on interactions between B. bassiana and western corn rootworm. In one laboratory assay, the effect of B. bassiana on western corn rootworm was tested by exposing 3rd instar larvae to treated filter paper for 24 hours and measuring mortality over 7 days. In a second assay system, we exposed neonate larvae to germinated corn seeds previously soaked in a solution of B. bassiana and covered in soil collected from agricultural fields. Larvae were allowed to feed on the roots for 10 days before assessing mortality. Identifying EPF isolates effective in causing mortality to western corn rootworm larvae will lead to a reduced reliance on traditional methods of management and further delay resistance to transgenic traits and crop rotation.