Natural Enemies of Wood-boring Beetles in Northeastern Temperate Forests and Implications for Biological Control of the Emerald Ash Borer (Coleoptera: Buprestidae) in North America

The emerald ash borer (hereafter EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a wood-boring beetle accidentally introduced into North America during the 1990s, and has since been killing millions of ash trees, Fraxinus spp. L. (Lamiales: Oleaceae), as it spreads across Canada and the USA. Native North American natural enemies, especially parasitoid wasps, are important mortality factors of EAB, but little information is available on their arrival and detection in EAB-infested regions, and their feasibility for augmentative biological control against EAB is uncertain. Two important native parasitoid groups, Phasgonophora sulcata Westwood (Hymenoptera: Chalcididae) and Atanycolus spp. Foerster (Hymenoptera: Braconidae), were investigated to determine (1) factors influencing their capacity to disperse, (2) vegetation and habitat characteristics influencing their local abundance and role in EAB mortality, (3) whether their populations can be augmented to increase parasitism of EAB, and (4) how best to detect and monitor their populations as EAB continues to spread. The weak dispersal capacity of P. sulcata suggests it should be released as pupae close to EAB if used in an augmentative biological control program. Forest vegetation and habitat structure determine local abundance of P. sulcata and Atanycolus spp., and tree biomass, tree condition, and floral resource availability are important predictors of high parasitism on EAB. Relocating parasitoid-infested ash logs to EAB-infested sites can significantly augment populations of native parasitoids to increase EAB parasitism by 64.8 ± 18.1 % three years after introduction. Purple prism traps can be used to detect and monitor changes in populations of relocated P. sulcata and Atanycolus spp. These findings improve our understanding of the role of native natural enemies in suppressing EAB population growth and slowing ash tree mortality in North America.Ph.D