Reproductive biology and diapause patterns of Oobius agrili, an egg parasitoid of emerald ash borer

Oobius agrili (Hymenoptera: Encyrtidae) is a solitary egg parasitoid of the invasive emerald ash borer (Agrilus planipennis).   We investigated the reproductive biology of O. agrili and characterized the weekly survivorship, fecundity, and diapause patterns of both diapaused and non-diapaused populations of O. agrili under four different temperature-photophase treatments: (1) warm (30^°C) with long-day (16 hr.) photophase, (2) warm (30^°C) with short-day (8hr.) photophase, and (3) cold (20°C) with long-day (16 hr.) photophase, and (4) cold (20°C) with short-day photophase.   Results of our study showed that regardless of the length of photophase, parental wasps of both diapaused and non-diapaused O. agrili survived significantly longer at 20^°C than at 30^°C.  Parental wasps of diapaused O. agrili populations laid similar number of eggs over their lifetime at 30°C and 20^°C.  However, wasps at 30°C deposited their egg load rapidly and those at 20°C laid eggs more steadily over time.  Non-diapaused O. agrili laid significantly fewer eggs at 20^°C than at 30^°C.  Higher proportions of the progeny produced by both diapaused and non-diapaused O. agrili were induced into obligatory diapause by short-day (8 hr) photophase, regardless of rearing temperature.  Specifically the diapaused populations in both short-day photophase treatments induced increasing proportions of diapaused progeny over time.  Relevance of these findings to the optimization of rearing conditions and release strategies for biological control of emerald ash borer is discussed.