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Title: Impact of Beauveria bassiana and imidacloprid, alone and in combination, used against emerald ash borer in a newly-infested ash nursery

Author
item Vandenberg, John
item CASTRILLO,, L. - CORNELL UNIVERSITY
item LIU,, H. - MICHIGAN STATE UNIV.
item Griggs, Michael
item BAUER,, L. - USDA-FOREST SERVICE

Submitted to: Proceedings of the Emerald Ash Borer and Asian Longhorned Beetle Research and Development Review 2006
Publication Type: Abstract Only
Publication Acceptance Date: 1/15/2008
Publication Date: 4/1/2008
Citation: Vandenberg, J.D., Castrillo,, L.A., Liu,, H., Griggs, M., Bauer,, L.S. 2008. Impact of Beauveria bassiana and imidacloprid, alone and in combination, used against emerald ash borer in a newly-infested ash nursery. Proceedings of the Emerald Ash Borer and Asian Longhorned Beetle Research and Development Review 2006. p. 50.

Interpretive Summary:

Technical Abstract: We are investigating the potential of Beauveria bassiana (strain GHA), alone or in combination with imidacloprid, for use against the emerald ash borer (EAB), Agrilus planipennis. We treated approximately 400 Fraxinus pennsylvanica and F. americana (height ca. 5-6 m) at a commercial tree nursery with fungus alone, imidacloprid alone at two rates, fungus plus the low rate of imidacloprid, or a formulation blank as control. Imidacloprid (Bayer) was applied as an early season drench in late May, and the fungus (BotaniGard ES, Laverlam) and formulation blank were applied biweekly three times between mid-June and mid-July. Initial EAB infestation was low, but in 2007, more than half the trees had beetle exit holes. We monitored spore deposition and estimated spore persistence on leaves and bark. At least 4 genotypes of B. bassiana were present in soil before any sprays and none of them was strain GHA. After sprays, we readily reisolated strain GHA from leaves (up to 6 weeks post-spray), bark and soil. A drop in fungal persistence with time was less pronounced on bark than on leaves. We have developed a real-time PCR method to quantify fungal DNA from environmental samples. We found efficacy of 1, 4 or 24-hour adult exposures to freshly-treated leaves and bark to be high. Beetles exposed to leaves and bark sampled 1 and 2 weeks after fungal application showed much lower mortality. Mortality of beetles exposured to leaves treated with both imidacloprid and the fungus was equal to, or greater than, that of beetles exposed to leaves treated fungus alone. We have completed 2 seasons of a multi-year study.