BIO-EFFICACY OF N-HEXANE, METHANOL AND AQUEOUS EXTRACTS OF SOME INDIGENOUS PLANTS IN THE MANAGEMENT OF MELON LADY BEETLE (EPILACHNA CHRYSOMELINA) FABRICIUS (COLEOPTERA: COCCINELLIDAE)

Abstract

Plant bioactive compounds are secondary metabolites synthesized by plants for self-protection against external factors. Many indigenous plants contain bioactive compounds that have bacterial, insecticidal, repelling and or ovicidal properties. This study evaluated the bioefficacy of methanol, n-hexane and aqueous extracts of Tithonia diversifolia, Azadirachta indica, Ocimum gratissimum, Anacardium occidentale, Eucalyptus globolus leaf and the seeds of Piper guineense in the management of Melon lady beetle, Epilachna chrysomelina in the laboratory. Contact toxicity of the different plants extracts was determined by topical application at 100 mg/l of each treatment on the beetles.  Area of preference test was used to determine their repellence as well as the residual effects of the extracts against the beetle. N-hexane and methanolic extracts of A. indica and P. guineense resulted in 100% mortality of the beetle within 4 hours of application which was comparable to the standard check (cypermethrin). The percentage mortality of n-hexane and methanol extracts of the other four plants are not significantly different from one another. However, 100% beetle mortality was observed at 10 hours of application in all the treatments. Similarly, significantly higher (>80%) repellence was observed in the beetle response to A. indica and P. guineense methanolic extract for two hours of introduction than other extracts used in the study. The methanolic extracts of A. indica and P. guineense had significantly higher residual percentage mortality (100% and 99.67%) respectively relative to other treatments applied within 24 hours of application. Therefore, methanolic extracts of A. indica and P. guineense can be incorporated into integrated pest management programme for the management of the E. chrysomelina.