Evaluation of recovery and monitoring methods for parasitoids released against Emerald Ash Borer

Authors: PARISIO, M. - State University Of New York- College Of Environmental Science And Forestry; GOULD, J. - Animal And Plant Health Inspection Service (APHIS); Vandenberg, John; BAUER, L. - Us Forest Service (FS); FIERKE, M. - State University Of New York- College Of Environmental Science And Forestry

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/22/2016
Publication Date: 12/24/2016
Citation: Parisio, M.S., Gould, J.R., Vandenberg, J.D., Bauer, L.S., Fierke, M.K. 2016. Evaluation of recovery and monitoring methods for parasitoids released against Emerald Ash Borer. Biological Control. 106:45-53.

Interpretive Summary: The emerald ash borer (EAB) is an invasive insect pest and the target of an extensive biological control campaign designed to minimize ash tree mortality. Three species of wasp parasites from the native range of EAB in northeast Asia are currently being released as biological control agents in North America. One parasitizes EAB eggs and the others attack larvae. In this study we compared methods used to monitor the wasps. These included destructive sampling of entire trees, the deployment of sentinel logs baited with EAB larvae, and traps. We recovered all three wasps after tree felling and examination of tree bark and phloem. We recovered only one of two larval parasites using bait logs, but all three wasp species were recovered using yellow pan traps. We found the traps to be as effective as both the bait logs and the labor-intensive tree-felling. We also found that the yellow pan traps were effective in recovering the egg parasite and one of the larval parasites at distances of 20 meters from release points. Because of their low cost and relative ease of deployment, we recommended that yellow pan traps be used as the preferred method for parasitoid recovery as monitoring efforts increase and the scale of the EAB biological control program continues to expand.

Technical Abstract: The emerald ash borer (Agrilus planipennis Fairmaire, EAB) is an invasive insect pest, and the target of an extensive biological control campaign designed to mitigate EAB driven ash tree (Fraxinus spp.) mortality. Since 2007, environmental releases of three species of hymenopteran parasitoids of EAB from China are being released as EAB biological control agents in North America: Oobius agrili (Hymenoptera: Encyrtidae), an egg parasitoid; Tetrastichus planipennisi (Hymenoptera: Eulophidae), a larval endoparasitoid; and Spathius agrili (Hymenoptera: Braconidae), a larval ectoparasitoid. Following release, current methods to document presence and establishment and to monitor dispersal of parasitoids in the field were simultaneously evaluated, including destructive sampling of entire trees, and deployment of egg sentinel logs (ESLs), egg sentinel cups (ESCs), larval sentinel logs (LSLs), and yellow pan traps (YPTs). Spathius agrili was the only species to be recovered using the sentinel log method (LSLs), however, all three species of parasitoids were recovered using YPTs and destructive sampling of trees. Results indicate YPTs are as effective as LSLs for S. agrili detection and as effective as destructive sampling of entire trees for detection purposes for O. agrili and S. agrili. YPT trap catches were significantly associated with egg parasitism by O. agrili, however, this was not true for larval parasitoids. Additional research indicated YPTs are effective in recovering O. agrili and T. planipennisi at distances of ~20 m from release points. It is therefore recommended that YPTs be used as the preferred method for parasitoid recovery as monitoring efforts increase and the scale of the EAB biological control program continues to expand.