Laboratory evaluation of the susceptibility of the cornfield wireworm, Melanotus communis, to U.S. commercial Beauveria and Metarhizium strains

The cornfield wireworm, Melanotus communis (Coleoptera: Elateridae), is an economically important pest of potatoes in the mid-Atlantic with feeding holes left on tubers resulting in reduced marketable yield, and increased susceptibility to phytopathogens. Insecticide use is limited due to environmental policy but mycoinsecticides can provide an alternative option for management of this pest. Entomopathogenic fungi, in general, can be efficacious for many common soil dwelling pests. A number of insect pathogenic fungi have been registered and commercialized in the U.S. for insect control but there is little data regarding efficacy against wireworms, and almost none for M. communis in particular. We conducted a series of soil incorporation and  immersion bioassays of the principle commercial Beauveria and Metarhizium strains (B. bassiana GHA, PPRI5339, ANT-03, ERL386, and M. brunneum F52), derived from their formulations, to better understand their potential efficacy for M. communis. Larvae were unusually resistant to infection in bioassays that paralleled methods and doses commonly used with other insects. Nevertheless, use of the best of these strains not as soil drenches but on nutritive granules that allow the applied rates to magnify as the fungi grow out and sporulate on the granules in soil, may still provide a useful management approach. The reported work is the first step in evaluating potential of any of these fungi for managing M. communis.