Protection of North American ash against emerald ash borer with biological control: ecological premises and progress toward success

Authors: Duan, Jian; GOULD, JULI - Animal And Plant Health Inspection Service (APHIS); QUINN, NICOLE - University Of Massachusetts, Amherst; PETRICE, TOBY - Us Forest Service (FS); SLAGER, BEN - Animal And Plant Health Inspection Service (APHIS); POLAND, THERESA - Us Forest Service (FS); BAUER, LEAH - Us Forest Service (FS); RUTLEDGE, CLAIRE - Agricultural Experiment Station, Connecticut; ELKINTON, JOE - University Of Massachusetts, Amherst; VAN DRIESCHE, ROY - University Of Massachusetts, Amherst

Submitted to: BioControl
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2023
Publication Date: 2/3/2023
Citation: Duan, J.J., Gould, J., Quinn, N.F., Petrice, T., Slager, B., Poland, T., Bauer, L.S., Rutledge, C., Elkinton, J., Van Driesche, R. 2023. Protection of North American ash against emerald ash borer with biological control: ecological premises and progress toward success. BioControl. https://doi.org/10.1007/s10526-023-10182-w.
DOI: https://doi.org/10.1007/s10526-023-10182-w

Interpretive Summary: The emerald ash borer (EAB) was accidentally introduced from Northeast Asia to the United States in the 1990s from wood-packaging materials in international cargoes. It has since spread to 35 U.S. states and killed tens of millions of ash trees in the United States and Canada. A biocontrol program was initiated against this destructive beetle in 2007 after U.S. federal regulatory agencies approved release of three Chinese parasitic wasps in EAB-invaded areas. In 2015, a fourth parasitic wasp from the Russian Far East was also approved for releases against EAB in the U.S. We reported the progressive suppression of this invasive beetle to conserve surviving North American ash communities in several northeastern states (Connecticut, Massachusetts, and New York) and Michigan, where the parasitic wasps were first released. Three of the four introduced biocontrol agents have successfully established, spread widely, and have suppressed EAB to low densities, which may allow surviving ash trees to regenerate and canopies to recover. This research contributed to the development of biocontrol-based, sustainable EAB management strategy.

Technical Abstract: The emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), an exotic wood-boring beetle native to Asia, was first discovered in 2002 in southern Michigan where it was causing widespread ash (Fraxinus spp.) mortality. Soon thereafter, a classical biological control program was initiated against this destructive pest. In 2007, after approvals were granted by federal regulatory agencies and the state of Michigan, releases of three EAB hymenopteran parasitoids from China began: Tetrastichus planipennisi Yang (Eulophidae), Spathius agrili Yang (Braconidae), and Oobius agrili Zhang and Huang (Encyrtidae). A fourth EAB parasitoid, Spathius galinae Belokobylskij (Braconidae) from the Russian Far East, was approved and first released in 2015. Currently, the four introduced parasitoids have been mass-reared and released in over 350 counties in 31 EAB-infested states. We examine the ecological premise of EAB natural enemy introductions and review progress in the development, implementation, and impact evaluation of the EAB biocontrol program for North American ash recovery. We also identify challenges in conserving native Fraxinus using biocontrol in the aftermath of EAB invasion and provide suggestions for program improvements as EAB spreads throughout North America. We conclude that the successful establishment, spread, and impact of T. planipennisi, S. galinae, and O. agrili in Michigan and several Northeastern states (Connecticut, Massachusetts, and New York) have resulted in low EAB densities, which may allow surviving ash to regenerate and recovery to canopy trees.