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Emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae), is rapidly invading North America and has inflicted extensive ash, Fraxinus spp., mortality in affected areas, altering composition and structure of wildland and urban forests. Insecticides can effectively protect ash on a small scale and classical biological control efforts have been implemented. In the U.S. emerald ash borer kills native ash so quickly, and populations are so mobile, that establishing an effective biological control program is challenging. Consequently, we assessed the compatibility of using reduced rates of the insecticide imidacloprid applied as a soil drench coupled with releases of three species of parasitic wasps. In this way we hope to slow the process of ash decline and prolong the window of opportunity to allow biological control agents to become established. We compared the efficacy and effects of i) full strength imidacloprid applications, ii) reduced rates of imidacloprid coupled with classical biological control, iii) classical biological control alone, and iv) untreated controls. We monitored emerald ash borer adult activity through trapping and destructive sampling for larvae, evaluated larval parasitization rates, and also assessed the native hymenopteran communities. Chemical treatments were not adequate to prevent ash canopy decline, but they also did not impede parasitization of emerald ash borer eggs or larvae. Two of the three classical biological control agents, Oobius agrili and Tetrastichus planipennisi , were recovered from trees treated with imidacloprid, demonstrating that they were successfully reproducing and indicating the compatibility of the two management strategies. Non-target hymenopterans appeared unaffected by the insecticide applications. Importantly we found no negative effects of the imidacloprid applications on native pollinators. Collectively these data suggest that judicious use of insecticides coupled with classical biological control may be an effective and potentially sustainable approach to managing invading populations of emerald ash borer. [ABSTRACT FROM AUTHOR]

Agrilus planipennis Fainnaire (Coleoptera: Buprestidae) is a wood-boring pest of Asian origin that has caused widespread mortality of ash, Fraxinus spp., in North America since its accidental introduction in the 1990s. Studies conducted at the epicenter of the infestation in the Great Lakes region have discovered several species of native parasitoids capable of utilizing A. planipennis-, however, little is known of how these natural enemy complexes vary across the shifting forest types and habitats encompassed by the expanding infestation. We characterized the assemblage of native natural enemies being recruited to A. planipennis at five sites in north-central Kentucky, where infestations have been documented since 2009. Through destructive sampling, dissection, and rearing of infested ash material, 12 native parasitoid morpho-species were found being recruited to A. planipennis, nine of which have not been reported previously. Catogenus rufus (F.) (Coleopter: Passandridae), Phasgonophora sulcata Westwood (Hymenoptera: Chalcididae), and Leluthia asgtigma (Ashmead) (Hymenoptera: Braconidae) have been discovered utilizing A. planipennis in more northerly infested regions of North America and were present in our study. Native hymenopteran parasitoid responses to A. planipennis presence and associated ash decline, measured using visual assessments of canopy decline, revealed a positive correlation between parasitoid guilds and ash decline. [ABSTRACT FROM AUTHOR]

RNA interference (RNAi) is a naturally occurring process inhibiting gene expression, and recent advances in our understanding of the mechanism have allowed its development as a tool against insect pests. A major challenge for deployment in the field is the development of convenient and efficient methods for production of double stranded RNA (dsRNA). We assessed the potential for deploying bacterially produced dsRNA as a bio-pesticide against an invasive forest pest, the emerald ash borer (EAB). EAB feeds on the cambial tissue of ash trees (Fraxinus spp.), causing rapid death. EAB has killed millions of trees in North America since its discovery in 2002, prompting the need for innovative management strategies. In our study, bacterial expression and synthesis of dsRNA were performed with E. coli strain HT115 using the L4440 expression vector. EAB-specific dsRNAs (shi and hsp) over-expressed in E. coli were toxic to neonate EAB after oral administration, successfully triggering gene silencing and subsequent mortality; however, a non-specific dsRNA control was not included. Our results suggest that ingestion of transformed E. coli expressing dsRNAs can induce an RNAi response in EAB. To our knowledge, this is the first example of an effective RNAi response induced by feeding dsRNA-expressing bacteria in a forest pest. [ABSTRACT FROM AUTHOR]