Low temperature induced quiescence in parasitoids Trichogramma evanescens Westwood and Trichogramma chilonis Ishii reared on Plodia interpunctella (Hübner): Its utilization as quality control for mass rearing

Abstract

Egg parasitoid, Trichogramma spp. is an important potential biological control agent for wide range of lepidopteran pests. Cold storage of host eggs has been proposed as a valuable technique for ensuring the release of sufficient parasitoid numbers whenever it is needed. Thus, the impact of low temperatures to induce quiescence in Trichogramma evanescens and Trichogramma chilonis was studied using eggs of Plodia interpunctella as hosts. Prepupae of the parasitoids Trichogramma evanescens and T.chilonis were stored for 15, 30, 45, 60 and 75 d at 4°C, following a 7 d period of acclimation at 10°C. Both parasitoid species seem to survive unfavorable temperature conditions by entering a state of quiescence. Parasitism, adult emergence, female proportion relative to male and F1 adult emergence were not affected by cold storage in either parasitoid for up to 30 d of storage. Parasitized host eggs of P. interpunctella can be stored for up to 60 d at 4°C for both parasitoids, but there was no emergence at 75 d. Results clearly show that there are specific intervals of cold storage during which the parasitoids can remain unaffected for relatively long periods of time. Although we observed some adverse effect in longevity and parasitism rates, the technique described here can be further utilized in mass rearing strategies of egg parasitoids for relatively long periods that will allow shipment and application in biological control programs.