The seasonality of two parasitoids (<i>Spathius agrili</i> and <i>Tetrastichus planipennisi</i>) of the emerald ash borer, <i>Agrilus planipennis</i>, and a survey for native natural enemies of the Emerald Ash Borer in eastern Tennessee

The emerald ash borer (EAB), Agrilus planipennisi Fairmaire (Coleoptera: Buprestidae), is an invasive species of bark borer native to eastern Asia whose primary habitat and food sources are trees in the genus Fraxinus. EAB is a major pest of all North American Fraxinus species and is responsible for mortality of millions of trees across its current North American range of 23 U.S states and 2 Canadian providences. After the discovery of EAB in Tennessee in 2010, parasitoid releases were started under the national EAB Biological Control Program. A research project was initiated in 2012 to 1) study the seasonality of the gregarious larval ectoparasitoid Spathius agrili Yang and the gregarious larval endoparasitoid Tetrastichus planipennisi Yang in the climate of eastern Tennessee, 2) determine the overwintering ability of the parasitoids in field releases, and 3) survey for potential native natural enemies of EAB. In 2013 a single generation of S. agrili developed from egg to pre-pupa in ca. 22 days before overwintering. Adult individuals of S. agrili from the same generation were found to have successfully overwintered in July 2014. No T. planipennisi successfully parasitized or overwintered. In 2013, S. agrili were successfully recovered from two field sites for the first time in eastern Tennessee after a single year of releases and successfully overwintering, indicating the ability of this species to establish. As in the previous study, no T. planipennisi were recovered. Three native parasitoids, Spathius floridanus Ashmead, an undetermined species of Spathius, and Atanycolus cappaerti Marsh & Strazanac, all known to be associated with EAB, were recovered at field sites. These recoveries represent the first documentation of these three native species associated with EAB in the southern U.S. These findings will help demonstrate the utility of S. agrili in the southern U.S. as a part of the national EAB Biological Control Program.

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