Phenology of EAB and Parasitoids in Kentucky

This Work Plan reflects a cooperative relationship between the University of Kentucky Research Foundation and Animal and Plant Health Inspection Service (APHIS), Plant Protection and Quarantine (PPQ). It outlines the mission-related objectives and anticipated accomplishments as well as the approach for conducting research investigating how classical biological control agents targeting the emerald ash borer are affected by regional variation in host plant and pest phenology, and the related roles and responsibilities of the parties as negotiated. II. Background – Considerable knowledge of the emerald ash borer (EAB) life cycle and released biological control agents has been generated through life table analyses in historically invaded areas of North America, primarily at northerly latitudes, but our understanding of host-parasitoid dynamics is less complete in the south, in part because of the relatively late arrival of EAB in the region. Although Fraxinus hosts are prevalent, forests in the south differ in composition and structure from their northern counterparts, and clear climatic differences are evident. There appears to be a more compressed one-year life cycle of EAB in the south, calling into question the predictability of parasitoid efficacy relative to what’s known from northern forests. As EAB continues to expand its geographic range in the south, it is critically important that we develop a clear picture of host development and host-parasitoid relationships so as to maximize efforts at effective mitigation through classical biological control. Of the four Asian parasitic wasp species approved and utilized in biological control releases in the US, three (Tetrastichus planipennisi, Spathius agrili, S. galinae) parasitize EAB larvae, and the fourth (Oobius agrili) is an EAB egg parasitoid. Tetrastichus planipennisi and S. galinae emerge in early spring, when mature EAB larvae are only available in the north where EAB often exhibits a two-year life-cycle. When these parasitoids emerge in the spring in the south, all EAB are in the overwintering chambers and are unavailable for parasitization; thus these species are unlikely to establish in more southerly latitudes. Spathius agrili emerges in the summer, >30 d after EAB emergence, and is well synchronized with EAB in the south where the one-year EAB life cycle prevails. Based on these observations, we expect Tetrastichus planipennisi and Spathius galinae to establish in the north (>40° N) and Spathius agrili to establish in the south. Kentucky EAB populations are ideally located (37-40° N) to evaluate this. The primary purpose of this agreement is to provide support to address knowledge gaps that exist for optimizing biological control efforts targeting emerald ash borer in the south. Before allocating additional resources for parasitoid releases in southerly latitudes, we must gain a greater understanding of whether the released insects are establishing, persisting, and building in numbers adequate to contribute to EAB population regulation. III. Objectives – We are conducting life table analyses of EAB in more recently invaded, southerly regions (