COMPARATIVE EVALUATION OF SOME BOTANICALS AGAINST KHAPRA BEETLE TROGODERMA GRANARIUM EVERTS (COLEOPTERA: DERMESTIDAE) ON STORED GROUNDNUTS

COMPARATIVE EVALUATION OF SOME BOTANICALS AGAINST KHAPRA BEETLE TROGODERMA GRANARIUM EVERTS (COLEOPTERA: DERMESTIDAE) ON STORED GROUNDNUTS

Abstract:

Khapra beetle, Trogoderma granarium Everts, is a serious storage insect pest of cereals and legumes in the tropical and sub-tropical regions of the world. The study was carried out in the laboratory at prevailing temperature (25±50C) and relative humidity (65±5%). Six improved groundnut varieties, which include SAMNUT 14, SAMNUT 17, SAMNUT 18, SAMNUT 21, SAMNUT 22 and SAMNUT 23 were examined for their susceptibility to T. granarium. Susceptibility of these varieties to the dermestid was determined with respect to kernel damage assessment, mean kernel weight loss and total larvae population. The food preference of the T. granarium larvae for the groundnut varieties after six months storage period was also investigated. SAMNUT 22 variety was the most susceptible while the least susceptible was SAMNUT 17. Further preliminary laboratory experiments involved screening of nine indigenous plant powders (leaves/seeds) against T. granarium larvae. Methanol extracts of five promising plant powders of Ricinus communis Linnaeus, Hyptis suaveolens Poit., Annona senegalensis Pers., Xylopia aethiopica Dunal and Khaya senegalensis Desr. were assayed for their effects on adult mortality and larval survival of T. granarium. Adult mortality and survival of larvae of T. granarium were significantly (P<0.05) different with increased all doses of crude extracts compared with the control. Adult mortality increased with the concentration of crude extracts and the duration of exposure of the insects on the treated groundnut kernels. The crude extracts were almost similar in their effectiveness. However, the potency of these extracts decreased rapidly due to volatilization. The five botanicals have good potentials as post harvest insect control agents, killing 89.0% of the insect three days after treatment at 3.0 ml per 50 grams kernels. R. communis crude extract has detectable harm on the kernels in causing discolouration and wrinkle. The most preferred of the treatment was the groundnut kernel coated with X. senegalensis crude extract. These results showed that the crude extracts of these plants may be exploited for Trogoderma control in stored products. Chemical analysis including infrared spectroscopy revealed the presence of amines, amides, aldehydes and ketone as the organic components in the test plants. Flavonoid was identified as a constituent of all the test plants except K. senegalensis. The results confirmed that X. aethiopica, in addition contained saponins, tannins, polyphenols,, steroids, glycosides and alkaloids. All the test plants contained polyphenols. In addition, alkaloids were detected in H. suaveolens. The chemical components detected in K. senegalensis include saponins. These components may be toxic to T. granarium. The results suggested that powders and crude extracts of the test plants could be used to suppress the menace of T. granarium.

COMPARATIVE EVALUATION OF SOME BOTANICALS AGAINST KHAPRA BEETLE TROGODERMA GRANARIUM EVERTS (COLEOPTERA: DERMESTIDAE) ON STORED GROUNDNUTS

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