Evaluation of the Insecticidal Potential of Six Plants Leaves Powders against Acanthoscelides obtectus Say on Stored Phaseolus vulgaris L.

Abstract

Most plant powders possess insecticidal properties and can be used to control insect pests on stored products. This study was conducted to evaluate insecticidal properties of Solanum melongena, Parkia biglobosa. Ipomoea batatas, Colocasia esculenta, Tridax procumbens and Terminalia catappa   against Acanthoscelides obtectus Say, an insect pest of stored Phaseolus vulgaris L. The leaves powder of these plants were assessed for aduticidal and reproduction inhibition potential as well as effect on seed weight in a completely randomized design at three treatment concentrations of 0.5%, 1.0%, 1.5% and 0 as the control. All the test plants investigated exhibited insecticidal activity against A. obtectus. Results showed a trend of variation in adult A. obtectus mortality according to post-treatment days and plants powder concentrations. Results analysis revealed that at 14 days after treatment, T. catappa at 1.5% had the highest significant (P=0.05) mortality of 40.21±0.71i. This was followed by S. melongena which had a similar effect of 39.41± 0.52i at the same concentration (1.5%). The least significant mortality was observed in the control. At 0.5% T.  procumbens, 0.5% Parkia biglobosa, 1.0% I. batatas and 1.0% C. esculenta, leaves powder had comparable effects. It was observed that the control had the highest number of progeny emergence of 181.33 ± 0.88g after six weeks while T. catappa significantly (P=0.05) inhibited progeny at 1.5% followed by 1.5% S. melongena and 1.5% C. esculenta.  Seeds of P. vulgaris treated with 1.5% T. catappa also had the least significant weight loss of 0.93 ± 0.17 g compared to the control which had the highest significant weight loss of 55.68 ± 0.79 g. Though all the plants studied caused significant increase in adult A. obtectus mortality, reduction in progeny emergence and P. vulgaris seed weight loss than the control. Terminalia catappa however, exhibited the best insecticidal potential. Terminalia catappa and Solanum melongena were very effective in inhibiting the reproduction and progeny emergence of A. obtectus, but increased adult mortality resulting in weight loss suggesting their potential in controlling A. obtectus on stored P. vulgaris.