The effect of neem-based pesticides (Azadirachta indica A. Juss.) on the natural enemies of the cabbage aphid and diamondback moth
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Date
2014-01-31
Authors
Magenya, Oscar Enos
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Abstract
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.
Description
Department of Zoology, 79p. The QK 495 .M52M3 2000