Are traditional neem extract preparations as efficient as a commercial formulation of azadirachtin A?

Neem seeds contain many substances with insecticidal properties, the main insecticidal ingredient being azadirachtin A. In developing countries such as Mali, a neem seed water extract is prepared by soaking ground seeds in water for three or seven days. The aim of this study was to check the effectiveness of this extract in terms of azadirachtin A extraction yield and insecticidal activity. The yield of extraction was 0.19 g azadirachtin A/100 g seeds. The concentration of azadirachtin A in the seed extract was approximately 200 mg l−1, eight times higher than the recommended concentration of commercial products (25 mg l−1). A comparison of the extractive capacity of different solvents indicated that the best solvents were water and methanol. The azadirachtin A concentration declined in extracts stored for more than 3 days at a temperatures higher than 30 °C. Bioassays were performed on target insects (the leafhopper Macrosteles quadripunctulatus, the moth Spodoptera littoralis and the tobacco whitefly Bemisia tabaci) in order to compare the insecticidal activity of the neem extract with that of the commercial product Neemazal T/S and of a solution of pure azadirachtin A. The bioassays conducted on the leafhopper and the moth demonstrated that the neem extract at the recommended concentration (25 mg l−1 active ingredient) was as effective as the azadirachtin-based commercial product at the same concentration, while for the control of the whitefly B. tabaci a higher concentration of the water extract was needed.

Research highlights► Neem-based insecticidal preparations used in Mali contain about 200 mg l−1 azadirachtin A. ► Insecticide treatments should be performed with freshly-prepared neem extracts. ► Neem extracts are as effective as azadirachtin-based commercial product on the leafhopper Macrosteles quadripunctulatus and the moth Spodoptera littoralis. ► When the main target insects are whiteflies, a higher concentration of the a.i. is needed.