Effect of host egg storage condition on the reproductive fitness of Oobius agrili (Hymenoptera: Encyrtidae), an egg parasitoid of the invasive emerald ash borer, Agrilus planipennis Faimaire (Coleoptera: Buprestidae)

Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae) is an important egg parasitoid of the emerald ash borer (EAB), Agrilus planipennis Faimaire (Coleoptera: Buprestidae). Shortly after EAB became a serious invasive forest pest in North America, this parasitoid (along with two species of larval parasitoids) was introduced in 2007 to the United States for biological control of this invasive beetle. In order to ensure successful establishment and spread of this parasitoid, additional releases are needed, requiring optimized laboratory rearing.  The purpose of this study was to determine the effects of relative humidity and EAB egg cold storage duration on host suitability to O. agrili. Laboratory-reared EAB eggs were stored at: 1) either 1.7^o C and 12.8^o C, 2) under high, medium, or low humidity, and 3) for 15, 30, 45, 60, 75, 90 or days, after which they were exposed to O. agrili under normal rearing conditions. Storage temperature did not affect rate of host attacks and parasitoid progeny development to adults or mature diapaused larvae, but reduced humidity and increased storage duration significantly reduced rate of successful parasitism and parasitoid progeny development. Ultimately, these findings can be used to optimize O. agrili rearing and potentially improve release efforts.