An artificial delay in emergence influences the number but not the fitness of adult emerald ash borer emerging from infested ash wood

Abstract

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.

Introduction and establishment of biological control agents for control of emerald ash borer (Agrilus planipennis) in Canada

“…We sampled trees in the fall at or near the time of leaf abscission or in the spring before green-up. The bolts we collected in spring were placed into a rearing room (24-26 °C, 40-50% relative humidity, 16:8-hour light: dark photoperiod) shortly after collection; bolts collected in the fall were stored either outdoors in an unheated shipping container (Fick and MacQuarrie 2018) or in a controlled environment chamber (4 °C, 0:24-hour light:dark photoperiod) for several months before being brought into the laboratory and placed in the rearing room. In the rearing room, the bolts from an individual tree were placed in cardboard drums (1.3 m height × 40 cm diameter; Greif Lok-Rim Fibre Drums, Delaware, Ohio, United States of America) that were sealed on the bottom with a steel round ring and on the top with a steel lock ring that sealed on the plastic lid and had a modified funnel that emptied into a capture chamber.…”

What makes an insect invasive? An introduction

“…The Emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is an invasive pest of ash trees in North America where it has reached a wide distribution. As infested logs are collected and kept in the laboratory for some time to obtain beetles for study, Fick & McQuarrie () investigated the effects of storage on the beetle's fitness. In contrast to anecdotal previous observations, they do not find strong effects on body condition and adult fitness, although the numbers of emerging beetles decreases after prolonged storage.…”