Overwintering of Trichogramma funiculatum carver (Hymenoptera: Trichogrammatidae) under semi-natural conditions

Abstract

Overwintering of Trichogramma (Trichogrammanza) funiculatum Carver was studied under seminatural temperate conditions by considering development time within eggs of the light brown apple moth, Epiphyas postvittana, and survival of adult wasps. Maximum and minimum mean development times were 84 and 63.6 d, respectively, for egg masses parasitized in early winter, and 72.6 and 51.5 d, respectively, for eggs parasitized mid-winter. Adults survived a maximum of 20 d in early winter and 22 d mid-winter. Maternal age did not influence either the development time or longevity of progeny. The lower temperature threshold at which T. funiculatum parasitized host eggs was between 8°C and 9°C. The relationship between temperature and development time in the laboratory was successfully used to predict the emergence of T. funiculatum at low temperatures and under the seminatural conditions. This implies that there is no diapause in T. funiculatum. Instead this species overwinters via a combination of slow development, or quiescence, coupled with increased adult longevity. This information should be useful in enhancing populations of this parasitoid in spring when T. funiculatum can suppress light brown apple moth and other pests.