Entomopathogenic Fungi from Minnesota Are Virulent Against Emerald Ash Borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), Adults in a Laboratory Autodissemination Device Assay

The emerald ash borer (EAB; Agrilus planipennis Fairmaire) is a deadly pest of ash trees (Fraxinus spp.) in North America. Chemical and biological control methods are already in use against EAB, but additional integrated pest management (IPM) strategies are needed to reduce EAB populations in remote, northerly forests on the edge of the infestation front, such as those in northern Minnesota, USA. One entomopathogenic fungus (EPF) isolate, Beauveria bassiana (Bals.-Criv) Vuill. CFL-A, deployed in autodissemination devices (ADDs) has previously shown promise in reducing EAB population growth. Additionally, EPF has been found to be associated with EAB in Minnesota. This study assessed the suitability of ten Minnesota-indigenous, and one commercial, EPF strains for potential use in ADDs targeting EAB adults. Fungal isolates spanned five genera, including Beauveria, Purpureocillium, Metarhizium, Clonostachys, and Samsoniella. Of those tested, Beauveria pseudobassiana S.A. Rehner and Humber EAB 16.8, Beauveria bassiana GHA, Metarhizium sp. Meta, and Purpureocillium sp. EAB 59-16-2 consistently reduced the mean survival time (MST) and probability of survival over time for EAB adults dropped into an EPF-containing ADD in the laboratory. Furthermore, these fungi were readily recovered from surface-sterilized EAB cadavers. Future ADD field trials using these isolates are warranted to validate their ability to reduce EAB population growth.