Abstract

The diamond back moth, Plutella xylostella Linnaeus, 1758 (Lepidoptera: Plutellidae) is improperly controlled with synthetic insecticides in vegetable crops. This practice, which pollutes the environment, led to human and animal health problems, and P. xylostella resistance. Neem (Azadirachta indica A. Juss) is reported in the literature as a natural alternative to synthetic insecticides in the control of many insect pests including P. xylostella. The aim of our study is to evaluate the toxic and post- treatment effects of neem leaves extracts on P. xylostella larvae in comparison to synthetic insecticides namely Conquest plus 388 EC and Cydim Super. Results revealed that exposure of third instars larvae (L₃) of P. xylostella on cabbage leaves treated with neem extracts for 24 h induced mortality rates between 1.67 and 6.67% (p > 0.05). Larvae consumed between 45.17 ± 4.48 and 210 ± 27.17 mm² of cabbage leaves surfaces after 24 h exposure (p < 0.05). The emerging rates of P. xylostella adults were lower for extracts of neem and were between 19.44 ± 6.81 and 20.55 ± 5.38% compared to the controls and insecticide treatments which rates were between 34.07 ± 6.35 and 70.37 ± 10.25% (p < 0.05). The neem leaves extracts were more effective than synthetic insecticides in the control of P. xylostella. Therefore they can be considered as a new hope in developing a management program on P. xylostella.

Key words: Neem leaves extracts, Plutella xylostella, cabbage consumed, mortality.