Accepted 26th April, 2017.
Field experiment was conducted to determine the effect of time and sequence of application of infective conidia and plant extracts on disease incidence, severity and yield of three cowpea varieties, namely; Ife brown, Ife bimpe and Tvx3236. The experiment was laid in a split plot design, cowpea plants in the first sub-plots were sprayed with the different concentrations of extracts and inoculated after forty eight hours. The second sub-plots were inoculated followed by application of extracts after forty eight hours while cowpea plants in the third sub-plots were inoculated followed by simultaneous application of extracts. Results from the study shows that disease incidence was significantly lower when plants extracts were applied two days before inoculation compared to application of the extract two days after inoculation or concurrent application of extract to the cowpea plants followed by inoculation. Similarly, disease incidence was significantly lower (20.4%) where extracts of D. stramonium were applied two days before inoculation. On the other hand, disease incidence was significantly higher (26.7%) when treatment with plant extracts preceded application of inoculum concurrently. Variations were also observed among the varieties of cowpea used in this study. There was no significant difference in disease incidence (28.1%) when J. gossypifolia extracts were applied two days after inoculation compared to when it was inoculated concurrently (30.4%) with extracts. Similarly, severity of the disease was significantly lower at higher concentrations of the extracts used in this study with corresponding increase in the percentage of normal seeds.
Keywords: Colletotrichum lindemuthianum, disease incidence, disease Severity, Cowpea varieties.