Biology of Diadegma sp. (hymenoptera: ichneumonidae), a parasitoid of Plutella xylostella (L.) (lepidoptera: yponomeutidae), from Reunion Island

Abstract

The genus Diadegma have some species able to parasite Plutella xylostella (L.) (DBM). Laboratory studies were carried out on a Diadegma sp. from Reunion Island to elucidate its ability to parasite DBM larvae, and to determine the influence of the temperature on its fecundity, longevity, oviposition and the consumption of cabbage leaves by parasitized DBM larvae. Parasitism rates were close to 70% for the L2 and L3 instar, and 53% for the L4. At 15°C, there were no progeny. At 20°C and 25°C, the percentage of parasitism was near 70%. At 29°C, the percentage parasitism was similar but the number of males produced was higher. Parasitized DBM larvae consumed 35% less leaf surface than non parasitized larvae. This Diadegma sp. is a possible candidate for introduction into tropical areas, where no tropically adapted Diadegma species are known and could complement Bacillus thuringiensis treated systems.