Use of Entomopathogens against Invasive Wood Boring Beetles in North America

Abstract

Anoplophora glabripennis and Agrilus planipennis are wood-boring beetles introduced from China to North America that are capable of killing healthy trees; A. glabripennis is polyphagous but attacks on maples (Acer spp.) are of major concern in North America, and A. planipennis attacks ash trees (Fraxinus spp.). Bioassays against A. glabripennis with entomopathogenic fungi identified that a strain of Metarhizium anisopliae (F 52) is virulent against adults. The primary deployment method investigated is propagation of the fungus within bands of non-woven fiber material. The fungal bands are then wrapped around tree trunks or branches, where wandering adults become contaminated with spores when walking across bands. Bands retain concentrations of viable conidia above the LC 50 for >3 months. Infections also decrease reproduction before females die, resulting in fewer offspring. A strain of the entomopathogenic fungus Beauveria bassiana (GHA) sprayed on infested ash trees causes mortality of adult A. planipennis as they emerge from tree trunks. Cover sprays also result in fungal infections of A. planipennis larvae, pupae and adults that have not yet emerged, due to bark splits that form over the larval galleries providing points of entry for fungal inoculum under the tree bark. In addition, recent bioassays identified a strain of Bacillus thuringiensis virulent against A. planipennis. Development of this microbial control agent for aerial application is planned to target adult beetles that feed throughout their lives on ash foliage in the tree canopy.