Protective effects of emamectin benzoate trunk injection on neighboring ash trees against emerald ash borer (Coleoptera: Buprestidae): potential benefits to classical biological control

Authors: Duan, Jian; CRANDALL, RYAN - University Of Massachusetts, Amherst; GROSMAN, DON - University Of Massachusetts, Amherst; Schmude, Jonathan; QUINN, NICOLE - University Of Massachusetts, Amherst; CHANDLER, JENNIFER - University Of Massachusetts, Amherst; ELKINTON, JOSEPH - University Of Massachusetts, Amherst

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2023
Publication Date: 4/21/2023
Citation: Duan, J.J., Crandall, R.S., Grosman, D., Schmude, J.M., Quinn, N., Chandler, J.L., Elkinton, J.S. 2023. Protective effects of emamectin benzoate trunk injection on neighboring ash trees against emerald ash borer (Coleoptera: Buprestidae): potential benefits to classical biological control. Journal of Economic Entomology. 116(3): 848–854. https://doi.org/10.1093/jee/toad074.
DOI: https://doi.org/10.1093/jee/toad074

Interpretive Summary: The emerald ash borer (EAB), a serious invasive forest pest, has killed millions of ash trees in the United States and Canada. Protecting North American ash trees against EAB has primarily relied on releasing and establishing introduced natural enemies (parasitic wasps). However, effective insecticide treatments are also needed for immediate protection of large, high-value North American ash trees against EAB. We determined whether ash trees injected with a systemic insecticide could protect untreated neighboring ash trees and whether the selective treatment of ash trees with the insecticide had adverse effects on the introduced natural enemies. Our findings indicate that the systemic insecticide treatment is effective in protecting treated trees against EAB infestation but not sufficient in protection of neighboring (untreated) trees. However, the selective treatment of ash trees with the insecticide has no adverse impacts on the establishment and abundance of introduced natural enemies and thus may be safely integrated with EAB biocontrol.

Technical Abstract: The emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is the most destructive invasive pest on ash (Fraxinus spp.) in the United States. We determined whether ash trees injected with emamectin benzoate (EB) could protect untreated neighboring ash trees within a 25-m radius. We also determined whether the selective treatment of ash trees with EB injections had adverse effects on the establishment and abundance of introduced larval parasitoids Tetrastichus planipennis Yang, and Spathius galinae Belokobylskij & Strazenac. In experiment one, trees were treated with EB and then retreated three years later. Five years post initial treatment, we found that 90% of treated ash trees retained healthy crowns, significantly higher than those of untreated control ash trees (16%). For experiment two, trees only received one treatment of EB and after two years 100% of treated ash trees retained healthy crowns, significantly higher than those of untreated ash trees (50%). In both experiments, we found that as distance from the central EB-treated tree increased, probability of a healthy canopy decreased and probability of symptoms of EAB infestation increased in neighboring (untreated) ash trees. However, such relationships did not result in significant differences in the proportion of neighboring (untreated) ash trees retaining healthy crowns between EB treatment and control radius plots. The introduced EAB biological control agents appeared to have established equally well between treatment and control plots. Findings are discussed in the context of integration of EB trunk injection with biological control for protection of North American ash.