A method for rearing Diadegma insulare (Hymenoptera : ichneumonidae) inthe greenhouse

摘要

The diamondback moth, Plutella xylostella (L.), is the most destructive insect of crucifer crops worldwide (Talekar and Shelton 1993, Annu. Rev. Entomol. 38: 275-301). With the development of widespread resistance in P. xylostella to nearly all classes of insecticides used against it, biological control agents, especially parasitolds, have attracted more attention. Diadegma insulare (Cresson) is the most important parasitoid of P. xylostella in North America and high rates of parasitism of P. xylostella caused by this parasitoid has been recorded in crucifer fields (e.g., Zhao et al. 1992, Great Lakes Entomol. 25: 253-258; Godin and Boivin 1998, Environ. Entomol. 27: 1157-1165). Nevertheless, in some years, P. xylostella may still not be adequately controlled by natural populations of parasitoids, and more research is needed to find ways to enhance the effects of D. insulare. Efficient rearing methods can facilitate research on D. insulare and increase its use in augmentative biological control for P. xylostella. However, other researchers have noted that D. insulare can be difficult to rear and often produces strongly male-biased sex ratios when in culture (Hu et al. 1998, Florida Entomol. 81: 526-534; Sieglaff et al. 1998, Florida Entomol. 81: 578-582). Herein, we report a simple method for rearing D. insulare on a laboratory colony of P. xylostella in a greenhouse. Using this method, we have maintained a colony of D. insulare in the greenhouse for over 9 months (13 generations) with an approximately 1:1 sex ratio.