Insecticidal activity of some botanical extracts against legume flower thrips and legume pod borer on cowpea Vigna unguiculata L. Walp

Abstract

Abstract Background Insect pests infestation is one the major constraints to cowpea production in many Sub-Saharan Africa including Nigeria. Control of these pests by farmers has been vastly by use of chemical pesticide which possesses lots of threats to human health and environments. This study is aimed at evaluating insecticidal efficacy of petroleum ether seed extracts of four plants (Azadirachta indica, A. Juss, Piper guineense Schum and Thonn, Annona muricata L., and Jatropha curcas L.) against legume flower thrips, Megalurothrips sjostedti Tryb., and legume pod borer, Maruca vitrata Fab. on cowpea as alternative eco-friendly options for the control of the cowpea field pests. Methods The extracts were applied at the rate of 10 ml/l of water at 1 week intervals for 6 weeks starting from 7 weeks after sowing (WAS) and replicate three times. The extracts were compared with lambdacyhalothrin at 5 ml/l of water as a standard check and untreated control. Results The results showed that all the treatments significantly (p < 0.05) reduced the population of legume bud thrips and legume pod borer compared to control. A. muricata followed by Piper guineense significantly (p < 0.01) reduced the population of legume flower thrips and legume pod borer as well as pod damage compared to other extracts. The percentage reduction of M. sjostedti and M. vitrata population by the extracts ranged from 52.07–69.28% and 57.78–78.52% respectively compared to control. Cowpea yield was significantly (p < 0.05) higher in plots treated with A. muricata and Piper guinense compared to other extracts. The efficacies of A. muricata and P. guineese were significantly (p < 0.05) higher than lambdacyhalothrin for the control of legume flower thrips and legume pod borer of cowpea. Conclusion Petroleum ether seed extracts of A. muricata and P. guineense were very potent against legume flower thrips and pod borer, and thus they can be effectively used by smallholder farmers for the management of cowpea post flowering pests. These plant products are readily available, environment friendly, and are suitable for low-income agriculture practiced in developing countries.