Evaluation of Seed Extracts of <i>Azadirachta indica</i>. Juss (Meliaceae) as Pesticide for the Treatment of Stored Bean Seeds

Abstract

This study sought to ascertain the potentials of extracted oil and various partition portions of the seed extract of Azadirachta indica in the control of insect (Callosobrochus maculatus) infestation of stored bean seeds. The extracted oil significantly enhanced feeding deterrence in the insect, grain damage was greatly reduced as well as weight loss and oviposition of the insects. The extracted oil at different doses significantly reduces oviposition and adult emergence of C. maculatus in the treated bean seeds. Methyl allyl disulphide, n-propyl benzoate, n-hexadecanoic acid, 9,12-octadecadienenoic acid, Methyl nonanoate, Methyl hexadecanoate, Linoleic acid, Oleic acid and Campesterol were the major components in the extracted oil through GC-MS analysis. Regression analysis of the available data on individual in the treated bean seeds confirm that significant reduction of the oviposition and adult emergence of Callosobrochus maculatus decreases with increasing doses of the extract. It was also observed that feeding deterrent, oviposition and adult emergence of the Callosobrochus maculatus of the bean seeds were found to reduce as the polarity of the partition portion of the extracts increases significantly. The preliminary phytochemical screening of the n-hexane and methanol extract revealed the presence of alkaloids, saponins, carbohydrates, steroids, triterpenes, glycosides, tannins and flavonoids. The findings have demonstrated the bioefficacy for the use of the extracted oil and various partition portion of the seed extract against insect infestation of the stored beans, hence strengthening the possibility of using it as an alternative to synthetic chemicals for the preservation of grains.