Abstract
Simple SummaryRearing of many hymenopteran egg parasitoids requires a reliable supply of host eggs. The parasitoid Paratelenomus saccharalis can be reared on eggs produced from field collected kudzu bug, Megacopta cribraria, however field-collected hosts obtained during reproductive diapause do not readily produce eggs and must be reared under a long day-length photoperiod to terminate diapause. In this study we found that an exogenous application of pyriproxyfen was able to terminate diapause, leading to a significant increase in egg production. The eggs produced by pyriproxyfen-treated M. cribraria were accepted by the egg parasitoid Paratelenomus saccharalis, however parasitoid emergence was reduced when compared to eggs from untreated hosts. When the effects of pyriproxyfen treatment on egg production and parasitoid emergence were evaluated together, the net increase in parasitoid yield due to pyriproxyfen treatment was approximately 87%. This method has the potential to increase parasitoid yield and reduce production costs in egg parasitoid rearing programs.The mass rearing of hymenopteran egg parasitoids requires an abundant supply of host eggs. The onset of reproductive diapause and subsequent decline in egg production poses a challenge for parasitoid rearing when using host colonies augmented by field-collected insects. We investigated the application of pyriproxyfen, a juvenile hormone analog, to induce oviposition in diapausing adult kudzu bugs, Megacopta cribraria (Fabricius) (Heteroptera: Plataspidae), and the use of eggs produced by pyriproxyfen-treated kudzu bugs to rear the egg parasitoid, Paratelenomus saccharalis (Dodd) (Hymenoptera: Scelionidae). The effects of pyriproxyfen and photoperiod treatments on host mortality, egg production, and rates of parasitoid eclosion from the eggs were used to calculate the parasitoid yield for the different treatment regimes. A combination of pyriproxyfen and a long-day photoperiod increased the parasitoid yield by 87% compared to acetone and a long-day photoperiod. The general applicability of JH-analog mediated egg production for parasitoid rearing is discussed.
Highlights
Hymenopteran egg parasitoids are frequently employed in biological control programs against a variety of native and adventive pest species [1,2,3,4,5]
We evaluated the application of pyriproxyfen to terminate diapause in M. cribraria and increase egg production and determined if pyriproxyfeninduced host eggs produce viable offspring
Differences in M. cribraria mortality between treatments were apparent in the SeptemDifferences in M. cribraria mortality between treatments were apparent in the Sepber collection, with survival curves diverging after approximately 20 days (Figure 3)
Summary
Hymenopteran egg parasitoids are frequently employed in biological control programs against a variety of native and adventive pest species [1,2,3,4,5]. The use of field collected insects as a source of host eggs is not feasible on a year-round basis for many Heteroptera due to reproductive diapause, as egg production is terminated during this period [11,12]. The hymenopteran egg parasitoid Paratelenomus saccharalis (Dodd) (Scelionidae) is a biological control agent of interest due to its known association with the invasive kudzu bug, Megacopta cribraria (Fabricius) [17]. The mass rearing of P. saccharalis as a biological control agent of M. cribraria requires a consistent and abundant supply of host eggs. As photoperiods below 12 h are present for much of the year reproductive diapause can be a substantial obstacle when field collected specimens are used for host egg production. We evaluated the application of pyriproxyfen to terminate diapause in M. cribraria and increase egg production and determined if pyriproxyfeninduced host eggs produce viable offspring. We estimated the parasitoid yield resulting from pyriproxyfen treatments using a model that combines the treatment effects on host fecundity and parasitoid eclosion in order to determine whether exogenous application of pyriproxyfen can be utilized to significantly increase parasitoid production
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