Laboratory Bioassay of selected Plant extracts for the management of Cowpea weevil Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Abstract

Laboratory bioassays of ethanol and hexane seed extracts of Azadirachta indica, Jatropha curcas, Piper guineense and Eugenia aromatic were conducted for contact and residual action against Callosobrunchus maculatus (F) on cowpea at ambient temperature of 27±2ºC and relative humidity of 75-80%. The extracts were applied at 25%, 50%, 75% and100% in three replicates. Ethanol extracts of E. aromatica and A. indica gave 80-100% mortality of larvae and adult C. maculatus from 50% -100% concentration at contact  while  hexane extracts of all plants from 50% concentration recorded 80-100% mortality on adult and 100% mortality on larvae  at all concentrations. Ethanol extracts of A. indica recorded highest mortality (80-100%) of adult at all concentration for residual action while hexane extracts of  E. aromatica from 75% gave highest mortality (40.67- 90.3%) at 24hours post treatment. Ethanol extracts of all the plants recorded 100% mortality on larvae at each concentration while hexane extracts only gave 100% mortality at 100% concentration with three extracts at 24hours post treatment. Hexane extracts has more contact effects while ethanol extracts has more residual effects on adult and larvae of C. maculatus. Both solvents are potent, thus should be exploited for the extraction of plant extracts for pests control.