Sequence of Application Benomyl and Plant Extracts in the Control of Cowpea Anthracnose Caused by Colletotrichum lindemuthianum Sensu Lato

Field experiment was conducted to compare the efficacy of hot water extracts of Ricinus communis, Jatropha gossypifolia and Datura stramonium at three concentrations (65, 50 and 30%) with benomyl in the control of cowpea anthracnose disease. The experiment was laid in a randomized complete block design. The total area of the farm (225m2) was subdivided into three. The first subplot was sprayed with the different concentrations of the extracts and benomyl followed by inoculation of the conidia of the fungus after 48 hours. The second subplot was sprayed with the spore suspension of the fungus followed by application of the extracts and benomyl after 48 hours. The third subplot was sprayed with the conidia of the fungus followed by immediate application of extracts or benomyl, and the control plot in each case was sprayed with distilled water. Result from the experiment shows that all the extracts at the tested concentration reduced the incidence and severity of the disease. D. stramonium at 65% concentration compares favourably with benomyl fungicide in reducing incidence and severity of infection. At 65% concentration of D. stramonium, incidence of the disease was 22% on pooled mean basis and this was not significantly different from that of benomyl (21%). The percentage of normal seeds recorded at 65% concentration of the extract was 85% and was not significantly different from benomyl (86%). In terms of disease severity, trace infections were observed at 65% concentration of the extract and benomyl. At lower concentrations of all extracts, significant variations were observed on incidence of disease and percentage of normal seeds when compared with that of benomyl. Application of the extracts and benomyl before inoculation reduced disease incidence compared to post inoculation of the fungus .The study therefore shows that extracts of these indigenous plants can be used as a substitute for the benomyl fungicide and that they are more effective when used as a preventive method in the management of anthracnose disease.