Influence of anthranilic diamide insecticides on emerald ash borer (Coleoptera: Buprestidae) larvae and establishment of introduced parasitoids in central Kentucky.

Abstract

Emerald ash borer (EAB) (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae) is an invasive pest of ash trees (Fraxinus spp.) in the United States. EAB is best managed via insecticides and biological control by wasps and woodpeckers. Neonicotinoids are often used for EAB due to cost and ease of use but are becoming restricted worldwide and are toxic to beneficial insects. Anthranilic diamides, a newer insecticide class, can manage beetle larvae with limited off-target effects. If diamides control EAB, they could replace neonicotinoids. We tested if drenches of chlorantraniliprole and cyantraniliprole at 3 rates controlled EAB larvae without affecting parasitoids in 41 recruit-sized white ash, Fraxinus americana L. (mean ± SE = 11.0 ± 0.7 cm diameter at breast height (DBH)) in central Kentucky 6 months after application. Only the high chlorantraniliprole rate (0.157 g a.i./L per cm DBH) significantly reduced EAB densities (1.3 ± 0.5 larvae per m2) relative to controls (9.5 ± 4.2 larvae per m2). Three treatments reduced parasitism by Phasgonophora sulcata Westwood relative to controls while no treatment affected nonnative parasitism or woodpecker predation. Thirty-six percent of larvae were parasitized even though the nearest parasitoid releases were over 20 km away and occurred 7 years prior. Spathius galinae Belokobylskij & Strazanac parasitism, never released in Kentucky at the time of this project, averaged 7.8 ± 2.9 % and is the furthest south this species has established in the United States. Chlorantraniliprole may control EAB in small diameter ash and reduce parasitism by P. sulcata but not introduced parasitoids.