Effects of cold storage, rearing temperature, parasitoid age and irradiation on the performance of Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae)

In this study, the effects of cold storage, rearing temperature, parasitoid age, and irradiation on the performance of the egg parasitoid Trichogramma evanescens were investigated. Pupae of T evanescens can be stored at 4 degrees C for up to 3 weeks without much loss of performance. The longevity and walking speed of adults emerging from chilled pupae significantly decreased after longer storage periods. The F, generation of adults which emerged from pupae stored up to 3 weeks was able to parasitize as well as the control. The parasitization rate was similar at 24, 27, and 30 degrees C, but significantly decreased at 33 and 36 degrees C. Although T evanescens developed to the pupal stage at 36 degrees C, no adult emergence was observed at this temperature. Developmental periods were longer at 24 degrees C than at higher temperatures. The optimum age for T evanescens to successfully parasitize host eggs ranged from 24 to 90h. The parasitization frequency of the 56-78h aged females was higher than for the other age groups. The daily egg laying pattern of female T evanescens adults was similar when they were reared on Ephestia kuehniella or Plodia interpunctella eggs. Gamma- or ultraviolet-irradiated and unirradiated host eggs were equally preferred by adult females. (C) 2008 Elsevier Ltd. All rights reserved.