Effects of intercropping of garlic or lettuce with Chinese cabbage on the development of larvae and pupae of diamondback moth ( Plutella xylostella )

The effects of intercropping on the growth and development of the diamondback moth (DBM),Plutella xylostella (Lepidoptera: Plutellidae), were investigated over five generations in a laboratory in Fuzhou, China. The treatments included intercropping Chinese cabbage (Brassica chinensis) with garlic (Allium sativum) (CG) and lettuce (Lactuca sativa) (CL), and the monoculture of Chinese cabbage as control (CK). The larval stage was significantly longer for the intercropping treatments compared to CK. Intercropping affected pupal weight but not the percentage of successful larvae population. Pupae tended to be 10 to 15% larger in the intercropping treatments for three of the five generations. The increase in size, pupa mortality was significantly higher with intercropping. Our findings suggest that intercropping can suppress the DBM populations in a long period rather than in a short term.   Key words: Plutella xylostella intercropping, diamondback moth, larval development, pupal mortality.