Effects of Aqueous Neem Leaves Extract on 4th Stage Larvae of Diamondback Moth Plutella xylostella L. (Lepidoptera: Plutellidae): New Perspectives

The diamondback moth Plutella xylostella Linnaeus, 1758 (Lepidoptera: Plutellidae) is improperly and excessively controlled with synthetic insecticides in vegetable crops. Neem (Azadirachta indica A. Juss) is reported to be an alternative natural insecticide in the control of many insect pests including P. xylostella. The aims of this study are to evaluate the lethal, antifeedant and post- treatment effects of neem leaves extract, on the 4th instar larvae of P. xylostella compared to those of 2 synthetic insecticides (Conquest Plus 388 EC and Cydim Super). Exposure of larvae on cabbage leaves (Ø = 90 mm) treated or not during 24 h, showed mortality rates between 1.67 and 13.33% and highest mortalities were due to neem extract and Cydim Super. Larvae fed with cabbage leaves disks treated with neem extract, consumed 271.67 ± 47.64 mm2 of the surface while in the control, the consumption was 309.50 ± 35.57 mm2. The emerging rate of P. xylostella adults was lower 57.78 ± 13.04% for neem leaves extract compared to controls and insecticide treatments whose rates were from 65.32 ± 7.34 to 89.63 ± 4.23% (p = 0). Neem extract caused wing damage to 21.86% of emerged P. xylostella, compared to the controls and insecticide treatments where all emerging adults were normal. The neem leaves extract could enhance the management of 4th instar larvae of P. xylostella by regulating its development to adults and deforming wings. Therefore it can be considered as a new hope in developing a management program against P. xylostella.

Author (s) Details

Abla Déla Mondédji
Laboratoire d’Ecologie et d’Ecotoxicologie (LaEE), Département de Zoologie et de Biologie Animale, Faculté des Sciences, Université de Lomé, Togo.

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