The searching capacity of two Trichogrammas species for Ocinara vrians in semifield

Key Words： Trichogramma, Ocinara varians, searching parasitic capacity, semifield

Abstract：      The gray silk moth, Ocinara varians Walker, is one of more serious pests in gardens in south China. Trichogramma spp. is an important egg parasitoid of this pest. In order to search for alternative control methods, the searching capacity of Trichogramma dendrolimi Matsumura and T. pretiosum Riley was tested by releasing adult parasites in cages (60 cm×60 cm×70 cm). Each cage included two host plants and had the same host egg numbers. The results show that, irrespective of whether parasitoids had prior experience of parasitizing O. varians eggs, the search capacity of T. dendrolimi and T. pretiosum declined as the parasitoid to egg ratio decreased. The rate of parasitism of T. dendrolimi was higher than that of T. pretiosum irrespective of prior experience. At a ratio of one parasitoid to one egg, adult T. dendrolimi that had prior experience of parasitizing O. varians eggs parasitized 50.7% of eggs, significantly higher than the proportion parasitized by larvae of this species that either had, or did not have, prior experience. Prior experience had no effect on the search efficacy of T. dendrolimi larvae, nor did it affect the search efficiency of adult or larval T. pretiosum.