DIADEGMA INSULARIS (HYMENOPTERA: ICHNEUMONIDAE) PARASITISM OF THE DIAMONDBACK MOTH (LEPIDOPTERA: PLUTELLIDAE) IN SOUTHWEST VIRGINIA

Abstract

Parasitization rates of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), by Diadegma insularis (Meus.) (Hymenoptera: Ichneumonidae) were determined in a pesticide-free cabbage planting in Southwest Virginia. Diadegma insularis, which parasitizes later instars of the host larvae but emerges from the host pupa, was responsible for 46% and 69% of the mortality in 1983 and 1984, respectively. Higher parasitization rates were found in pupae collected from the Abbott and Cobb #5 cabbage variety, even though infestations of diamondback moths were higher on other varieties. Although most pupation of the diamondback moth occurred on the lower cabbage leaf surfaces, the proportion of parasitized hosts found on upper versus lower leaf surfaces did not differ significantly.