Effects of cold storage on field and laboratory performance of Trichogramina carverae (Hymenoptera: Trichogrammatidae) and the response of three Trichogramina spp. (T-carverae, T. nr. brassicae, and T-funiculatum) to cold

Delaying emergence of Trichogramma spp. is critical for commercial production. Here, diapause induction was considered for three species (Trichogramma nr. brassicae Bezdenko, Tri-chogramma carverae Oatman & Pinto, and Trichogramma funiculatum Carver), and the effect of storage temperature (4degreesC, 8degreesC, and 10degreesC) and tune (1-8 wk) was investigated for T carverae. For all species, percentage of emergence was lowered after an initial diapause induction period (28 d at 14degreesC and a photoperiod of 8:16 [L:D] h) and lowered further after 1-mo storage at 3degreesC and a photoperiod of 0:24 (L:D) h. No wasps emerged after 2 mo of storage, suggesting that true diapause was not induced. The effect of 1-8-wk storage on wasp quality, vas investigated for T carverae both in the laboratory and the field. Initial fieldwork suggested that this species could be successfully stored at 10degreesC under Continuous light (after 5-d development at 25degreesC and a photoperiod of 16:8 [L:D] h) without reducing the ability. of wasps to parasitize eggs in the field. In a second experiment, storage temperatures lower than 10degreesC and storage times 3 wk or longer had a negative impact on emergence and longevity, and effects were not additive. Negative effects may partly, reflect size changes, because size decreased in response to storage time, and there was an interaction between time and temperature effects oil size. Storage time was the major factor influencing fecundity and field success; both fitness measures,were reduced after storage of 3 wk or longer. T carverae can therefore be successfully stored for Lip to 2 wk without detrimental effects, and 10degreesC is the preferred storage temperature. T carverae seems to Survive unfavorable temperature conditions by entering a state of quiescence.