ASSESSMENT OF TRICHOGRAMMA SPECIES FOR BIOLOGICAL-CONTROL OF FOREST LEPIDOPTERAN DEFOLIATORS

In a laboratory study, we determined the potential of three Trichogram ma (Hymenoptera: Trichogrammatidae) species, T. brassicae Bezdenko, T. minutum Riley and T nr. sibiricum Sorokina, for biological control ag ainst six species of forest lepidopteran pests, black army cutworm, he mlock looper, eastern spruce budworm, western spruce budworm, white-ma rked tussock moth, and gypsy moth. Females of each parasitoid species were offered eggs from each of the six host species. Parasitization an d the effect of the host species on the emerging progeny were examined and recorded. Trichogramma minutum had the broadest host range and su ccessfully parasitized four host species out of the six offered. Trich ogramma nr, sibiricum had the narrowest host range and parasitized onl y two species of hosts. Of the six host species, black army cutworm wa s the most preferred by all three Trichogramma species; white-marked t ussock moth and gypsy moth were not parasitized by any parasitoids. Th ere was a positive correlation between the size of female offspring an d their corresponding egg complement in all three parasitoid species. The developmental time of parasitoids from egg to adult was influenced by both the parasitoid and host species. Our results suggest that T. minutum has the greatest potential for biological control against vari ous forest lepidopteran pests and that the black army cutworm may be t he best target candidate for further study.