An artificial delay in emergence influences the number but not the fitness of adult emerald ash borer emerging from infested ash wood.
Emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is the most significant invasive forest pest in North America. Laboratory research on this species requires sources of adult and larval insects that are of the same fitness as those present in the wild. Production of adult EAB relies on flushing adults from logs which are subject to cold storage for some period prior to use. The effect of this storage on the number of insects emerging or the fitness of those that emerge has not been investigated. We subjected logs of EAB-infested white ash, Fraxinus americana L. (Oleaceae), to 7-14 months of cold storage and quantified the number of insects that emerged, the time to emergence, and the body condition of adults as a measure of fitness. Body condition was evaluated using Soxhlet fat extraction and water weight. No published methods for Soxhlet fat extraction were available for this species so we developed extraction protocols. The number of insects emerging decreased with time, but fitness (i.e., fat and water content) did not decrease. Time to emergence did increase but only in the longest storage treatment, whereas a comparison of male vs. female emergence provides evidence for protandry in EAB. Rearing programs for EAB using wood from cold storage should adjust the amount used to produce a given number of insects but the quality of those individuals emerging will not be affected. We suggest that those insects that perished during storage were of lower quality when entering diapause and thus would serve as poor-quality host in rearing programs for natural enemies of EAB. These data also provide evidence for one pathway of introduction for EAB, suggesting that refrigeration in transit was required for EAB to remain viable and establish its beachhead in North America.