Effect of cold storage on the viability of Exorista japonica (Townsend) (Diptera: Tachinidae) pupae of an important parasitoid of noctuid larvae

摘要

Exorista japonica (Townsend) is a polyphagous parasitoid that attacks several lepidopteran pest species and it has been well known as a powerful natural enemy showing the high parasitism on noctuid larvae. For usage of this parasitoid in biological control of insect pest larvae, we established the effective storage condition for stockpiling this parasitoid. Emergence rate of E. japonica pupae stored at 4.0 degrees C, emergence rate was higher than that at other cold storage temperature conditions. Storage at 10.0 degrees C was deleterious to the parasitoids' emergence below 50.0% emergence rate. Preconditioning by exposing pupae to 10.0 degrees C for 72 h before storage at 4.0 degrees C showed a significant low emergence rate, even though female longevity was relatively high. Cold storage durations had a significant effect on emergence, fecundity, and female longevity. After 4 weeks storage at 4.0 degrees C, emergence rate significantly decreased. The fecundity and longevity of female significantly decreased even though pupae were stored at 4.0 degrees C for only 1 week. Cold storage had an effect on sex ratio, fecundity, and female longevity of F1 progeny. The proportion of females in F1 progeny produced by cold stored individuals was much higher than that of the control. Cold storage may decrease the quality of parasites. However, E. japonica pupae can be successfully stored up to 3 weeks so that sufficient supply of this parasitoid at a release time would be possible through a mass production with a cold storage.