EFFECTS OF WILD AND CULTIVATED HOST PLANTS ON OVIPOSITION, SURVIVAL, AND DEVELOPMENT OF DIAMONDBACK MOTH (LEPIDOPTERA, PLUTELLIDAE) AND ITSPARASITOID DIADEGMA INSULARE (HYMENOPTERA, ICHNEUMONIDAE)

The effects of wild and cultivated Brassicaceae host plants on diamond back moth, Plutella xylostella (L.), oviposition, egg hatch, larval su rvival, infestation level, parasitism rate by Diadegma insulare (Cress on), and the developmental time and sex ratio of D. insulare were stud ied. Diamondback moth egg laying was highest on the Brassica crops, es pecially broccoli, and lowest on wild Brassicaceae, especially Bertero a incana L. DC. and Erysimum cheiranthoides L. Percentage of egg hatch was not significantly different among host plants. Diamondback moth l arval survival was generally higher on the Brassica crops than on wild Brassicaceae and there was no survival on Barbarea vulgaris R. Br, De velopmental time of diamondback moth larvae was generally longer on th e wild Brassicaceae than on the Brassica crops. Percentage of parasiti sm by D. insulare was lowest on B. incana, Lepidium campestre R. Br. a nd E. cheiranthoides. Percentage of parasitism was higher when diamond back moth larvae fed on B. kaber than on the wild Brassicaceae. When f ea on E. cheiranthoides, Thlaspi arvense L., and B. incana, parasitize d diamondback moth larvae look significantly longer time to develop to D. insulare pupae than when they were fed on the other Brassicaceae p lants. The female/male sex ratio was higher on Brassica species than o n non-Brassicas. Diamondback moth infestation and percentage of parasi tism in the field were higher on broccoli than on the other Brassica c rops, but the proportion of D. insulare females versus males was not s ignificantly different. The presence of wild Brassicaceae, especially B. vulgaris and B. kaber, in the field could reduce diamondback moth p opulations, increase tile impact of D. insulare, provide a reservoir f or insecticide-susceptible diamondback moth, and increase the success of diamondback moth management programs.