Comparative dispersal of Trichogramma evanescens and Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) in relation to environmental conditions

Insect parasitoids have to disperse to locate host habitat and host, and individuals of small species, such as egg parasitoids, are expected to be very sensitive to climatic conditions during dispersal. The effect of 16 environmental variables on the spatio-temporal pattern of dispersion of Trichogranma evanescens Westwood, originating from Egypt, and Trichogramma pretiostum Riley, originating from Quebec, was quantified. In T, evanescens, the accumulation of solar radiation at temperatures >15 degrees C had a significant effect on its dispersion. When >15,000 kJ/m(2) were accumulated more parasitism was observed in a larger area. When wind blew above 15 km/h for >4 h in a day, dispersion also decreased significantly. In T. pretiosum, accumulated solar radiation had no significant effect, whereas it took 8 h of wind >15 km/h to significantly reduce dispersion. T. evanescens, a warm climate species, thus appears to be more sensitive to temperature. Its relatively higher sensitivity to wind condition may indicate that this species is adapted to aggregated or rare hosts, which require more flight control for location.