The effect of neem-based pesticides (Azadirachta indica A. Juss.) on the natural enemies of the cabbage aphid and diamondback moth
Magenya, Oscar Enos
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The effect of pesticides from the Neem tree (Azadirachta indica A. Juss) on the natural enemies of cabbage aphid and Diamondback moth was investigated. The test on the effect of Neem products on the reproductive potential of Diaeretiella rapae (an aphid parasitoid) was also carried out. Results showed that the parasitoid survival was significantly higher after the application of Neem powder (0.5% AZA) and enriched Neem oil (0.5% AZA) treatments than the Dimethoate treatment. Neem powder positively influenced survival 3 days and 6 days after the treatment applications, though not significantly. Neem treatments caused significantly higher first generation emergence from the treated parasitoids than those treated with Dimethoate but lower than the control treatment. Similar results on the number of parasitoids with deformed wings were recorded. Observations on the treatment effect on the parasitoid survival in aphid mummies showed no significant differences for D. rapae, Alloxysta sp. and Pachyneuron sp. seven days after the treatment applications. However, Neem treatments recorded significantly higher differences for Pachyneuron sp. and for the total parasitoid emergence, fourteen days after the treatment applications. Results on Neem repellency against D. rapae, showed that Neem powder was the least repellant treatment. A study on the effect of Neem on cabbage aphid and DBM natural enemies was carried out in the field and in the laboratory. Results showed that Neem powder seemed to enhance the emergence of Diadegma sp., 0. sokolowskii, D. rapae and Alloxysta sp., though not significantly. Significantly lower syrphid fly numbers were recorded after the Neem treatment but there were no significant differences recorded for ladybird beetles after the treatment applications.
- MST-Zoological Sciences