The mating and oviposition behavior of the invasive emerald ash borer (Agrilus planipennis), with reference to the influence of host tree condition

Emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is an invasive wood-boring beetle first detected in North America in 2002. Relatively little is known about the factors affecting the mating and oviposition behavior of EAB, even though they could have implications for the management of this species. Consequently, we conducted field surveys in Michigan to observe the diurnal behavior of EAB adults, in addition to examining how their behaviors associated with reproduction varied in relation to the size and condition of host trees. We observed most EAB adults between 11:00 and 15:00, and this pattern was the same for both sexes and for all of the specific behaviors examined (feeding, flying, mating, resting, and walking). Regarding host tree size and crown condition, we consistently found that the most EAB eggs, adults, mating pairs, and ovipositing females were observed on intermediately stressed trees with 40-60 % crown reductions (likely resulting from earlier EAB infestations). Additionally, host tree crown condition appeared to be a more important factor than diameter at breast height. Our results therefore provide support to the hypothesis that host tree crown (stressing) condition influences EAB oviposition behavior. Determining which trees are likely to contain the most EAB eggs should help to guide efforts for releasing and promoting the establishment of parasitoids utilized in biologic control. However, future work should attempt to experimentally test the hypothesis that host tree condition (e.g., crown reduction) drives EAB oviposition behavior, and investigate the fitness implications of these host choices.