Efficacy of Jatropha curcas Leaf Extract in the Control of Brown Blotch Disease of Cowpea (Vigna unguiculata)

Abstract

ABSTRACT A study on the use of Jatropha curcas leaf extract in the control of brown blotch disease of cowpea caused by Colletotrichum capsici was carried out in vitro and in the field. The laboratory experiment made use of extract prepared by using cold and hot water. Treatments were the extract at concentrations 20, 40, 60, 80 and 100%. These concentrations were compared with benomyl (benlate) solution and a control. Five milliliters of each treatment was applied to Petri dishes containing 25 ml of PDA medium. Each Petri dish was then inoculated with Colletotrichum capsici and incubated for 7 days at 28°C. The field experiment made use of four treatments, consisting of J. curcas leaf extract, 100 g of detergent solution, benomyl solution and a control. Treatments were sprayed twice (at 50 and 58 dap, respectively) on the cowpea seedlings, after inoculating them with C. capsici at 42 dap. The results showed that J. curcas leaf extract reduced mycelial growth of C. capsici in vitro. However, the hot water extract was more effective than cold water extract. The results also indicated that J. curcas leaf extract was effective in controlling brown blotch disease in the field. The action of the leaf extract in the measured parameters was comparable to the effect of benomyl solution. These findings indicate a promising potential for J. curcas in the management of plant diseases.