Optimizing application rates of Metarhizium brunneum (Hypocreales: Clavicipitaceae) microsclerotia for infecting the invasive Asian longhorned beetle (Coleoptera: Cerambycidae)

Authors: CLIFTON, ERIC - Cornell University; GARDESCU, SANA - Cornell University; Behle, Robert; HAJEK, ANN - Cornell University

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/2020
Publication Date: 9/25/2020
Citation: Clifton, E.H., Gardescu, S., Behle, R.W., Hajek, A.E. 2020. Optimizing application rates of Metarhizium brunneum (Hypocreales: Clavicipitaceae) microsclerotia for infecting the invasive Asian longhorned beetle (Coleoptera: Cerambycidae). Journal of Economic Entomology. 113(6):2650-2656. https://doi.org/10.1093/jee/toaa222.
DOI: https://doi.org/10.1093/jee/toaa222

Interpretive Summary: The Asian longhorned beetle is an invasive wood-boring beetle that threatens hardwood trees in urban and forest habitats in North America often resulting in tree death. To assist with control and eradication efforts, application rates and formulation treatments of the beneficial insect fungal pathogen known as Metarhizium were studied to provide biological pest control. The study demonstrated that an effective concentration of fungus was obtained by both higher application rates of a standard formulation and by using a concentrated formulation. Demonstrating successful beetle control with applications of this biological fungus validates this environmentally safe technology to protect hardwood resources in the urban and natural landscapes from the damage caused by unwanted invader.

Technical Abstract: The Asian longhorned beetle [Anoplophora glabripennis (Motschulsky)] is an invasive wood-boring beetle that threatens urban trees and forests in North America and Europe. The entomopathogenic fungus Metarhizium brunneum Petch strain F52 can infect and kill A. glabripennis adults, and this fungus is registered for commercial use in the United States. The current study tested different formulations and application rates of M. brunneum microsclerotial granules for management of A. glabripennis adults. Three application rates (1x–3x: 0.03-0.09 g/cm2) of M. brunneum microsclerotial granule formulation were exposed on tree trunks for 4-week periods during May–September. Higher application rates had better retention on the more thickly coated surface, rather than greater weathering loss. Microsclerotia at the 2x application produced 18 times more conidia than 1x, resulting in faster A. glabripennis mortality in quarantine laboratory bioassays. The 3x and 2x rates were not significantly different in retention, conidia, or mortality, but 2x produced the most conidia per gram applied. An augmented 2x formulation, using granules containing 70% M. brunneum by weight rather than 50%, produced significantly greater conidial densities and more rapid beetle mortality.