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Azadirachtin Biopesticide: a Review of Studies Conducted on Its Analytical Chemistry, Environmental Behaviour and Biological Effects

Document Type

Article

Journal/Book Title/Conference

Journal of Environmental Science and Health Part B Pesticides Food Contaminants and Agricultural Wastes

Volume

31

Issue

4

First Page

913

Last Page

948

Publication Date

1996

Abstract

This paper provides a brief review of studies conducted in our laboratory on the analytical chemistry, environmental behaviour and biological effects of azadirachtin‐A, a neem‐based pesticide.

Azadirachtin‐A (AZ‐A) was isolated from samples of neem seed kernels, leaves, bark, root and stem, obtained from Kanthayapalayam, South India. The extracts were subjected to column cleanup and AZ‐A concentration was quantified by using a high‐performance liquid chromatographic (HPLC) method. A flow diagram is given describing the procedures involved. AZ‐A was also isolated from four commercial formulations and from several forestry substrates, and its concentration in each sample was quantified by HPLC.

To investigate the environmental behaviour of AZ‐A, five studies were conducted: (i) persistence of AZ‐A on balsam fir and red oak foliage, (ii) dissipation of AZ‐A in forest nursery soils, (iii) leaching in sandy loam forest soil, (iv) adsorption and desorption of AZ‐A in sandy loam soil, and (v) rate of hydrolysis in buffer solutions and natural waters. A summary of the data is given in the paper.

The biological effects of azadirachtin on two‐spotted spider mites infecting young trembling aspen plants was studied after applying AZ‐A and its four formulations onto aspen leaf discs. The repellency, oviposition deterrence, mortality and fecundity were investigated. The data indicated that the toxic effects were significantly influenced by AZ‐A concentration and formulation ingredients.

The photostability of AZ‐A was examined following application onto red maple foliage and the effect of three UV stabilizers on the rate of degradation was investigated over a 10‐d period. The data indicated that the half‐life of degradation could be increased on maple foliage by the addition of 2,4‐dihydroxybenzophenone to AZ‐A at a concentration of 1:1 w/w. In addition, the mechanisms of energy transfer between AZ‐A and the UV protectant molecules are also described.

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