Comparative Efficacy of Three Techniques for Monitoring the Establishment and Spread of Larval Parasitoids Recently Introduced for Biological Control of Emerald Ash Borer, Agrilus planipennis (Coleoptera: Buprestidae)

Authors: RUTLEDGE, CLAIRE - Agricultural Experiment Station, Connecticut; VAN DRIESCHE, ROY - University Of Massachusetts, Amherst; Duan, Jian

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/2/2021
Publication Date: 7/5/2021
Citation: Rutledge, C.E., Van Driesche, R.G., Duan, J.J. 2021. Comparative efficacy of three techniques for monitoring the establishment and spread of larval parasitoids recently introduced for biological control of Emerald Ash Borer, Agrilus planipennis (Coleoptera: Buprestidae). Journal of Economic Entomology. 161:1-8. https://doi.org/10.1016/j.biocontrol.2021.104704.
DOI: https://doi.org/10.1016/j.biocontrol.2021.104704

Interpretive Summary: The emerald ash borer (EAB) is a serious invasive forest pest that has killed tens of millions of ash trees in the United States and Canada. Two parasitic wasps (Tetrastichus planipennisi and Spathius galinae) attacking EAB larvae have been introduced from Northeast Asia to the U.S. for biocontrol of the pest. Determining if these introduced beneficial wasps have established, spread, and persisted in the released forests requires reliable and efficient techniques to recover released natural enemies. We compared three sampling techniques for detection of these three beneficial wasps: 1) debarking the lower trunk of ash trees, 2) yellow pan traps, and 3) sentinel logs containing EAB larvae. Debarking trees was the most efficient method for detecting S. galinae and sentinel logs were the most efficient sampling method for detecting T. planipennisi.

Technical Abstract: We compared three methods for detection of two larval parasitoids introduced for the control of the emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae): Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) and Spathius galinae Belokobylskij and Strazanac (Hymenoptera: Braconidae). These methods were 1) debarking the lower 2 m of ash trees, 2) yellow pan traps (YPT), and 3) sentinel logs containing manually inserted late-instar EAB larvae. The parasitoids studied were released in a mixed hardwood forest in Cromwell, Connecticut from 2015 – 2017 and had established self-sustaining populations before this experiment. In 2019, we deployed all three detection methods along two transects (4.6 km and 5.7 km long, respectively) radiating out from the parasitoid release area. All three methods detected both parasitoid species. Tetrastichus planipennisi was detected at the furthest transect site on both transects and S. galinae was detected at the terminus of the 4.6 km transect. Sentinel logs were the most efficient method for capturing T. planipennisi, with a labor requirement of 2.4 h /detection (139 h / 57 broods). Debarking, in contrast, was the most efficient method for S. galinae, with a labor requirement of 3.6 h /detection (172 h / 48 broods). YPT were the least efficient technique, capturing only 15 T. planipennisi and 9 S. galinae wasps for the entire trapping period at Cromwell, a labor requirement of 18.7 h / per detection (280 h /15 adults) and 31.1 h /detection (280 h /9 adults), respectively. We discuss the advantages and disadvantages of these three techniques.