ABSTRACT

 Field trials were conducted in 2006 and 2007 late cowpea cropping season between the months of August and November in the Research Farm of Michael Okpara University of Agriculture, Umudike, to assess the efficacy of leaf extracts of Gmelina arborea, Chromoleana odorata and Anacardium occidentale in the control of anthracnose disease of cowpea induced by Collectotrichum destructivum . The study was designed to evaluate the effects of the different plant extracts on the disease development, growth and yield performance of cowpea inoculated with anthracnose pathogen, with a view to identifying the most effective extract that can be used in the control of the disease without any ecological disturbance as does synthetic chemicals. Seeds of cowpea (Ife Brown) disinfected and inoculated with spores of Colletotrichum desructivum (10) were used for the study. The field trial was a three factor experiment; (leaf extracts, seed inoculation and seed disinfection) in a randomized complete block design and replicated three times. Cowpea was spaced at 0.5m x 0.5m, sown in plots measuring 3m x3m. Data were collected fortnightly for growth characteristics and disease indices, such as plant height (cm), number of branches, number of leaves per plant and days to 50% flowering, disease incidence and disease severity, while the data on yield performance were taken at maturity for grain yield (kg/ha), number of pods per plant, number of seeds per pod, pod length (cm), 100-seed weight (g) and percent yield losses. Data generated from the study were subjected to statistical analysis using enhanced Genstat Statistical Software for Analysis of Variance (ANOVA) and the Fisher's LSD was used in mean separation. Results of data analysis showed that significant (P<0.05) differences existed among the leaf extracts used as treatments. The highest (7 1.03%) and lowest (18.06%) incidence of anthracnose disease on cowpea were recorded in untreated plots and Siam weed extract-treated plots, respectively. Anthracnose disease severity indices of 7.17 and 0.59 were recorded for the control and cashew extract-treated plots respectively. Results of the effects of plant extracts on the various growth components, yield components and yield of cowpea plants were significant> Plots sprayed with the plant extracts significantly enhanced growth and yield when compared with the control plots. Also, plot whose seeds were disinfected significantly increased yield components and grain yield of cowpea plants relative to their undisinfected counterparts. In most cases, inoculation of cowpea seeds with the anthracnose pathogen significantly reduced growth and yield of cowpea plants. The highest grain yield of 4,377.0kg/ha and 1,980.0kg/ha was obtained in plots sprayed with benomyl and whose seeds were disinfected but not inoculated with the pathogen in 2006 and 2007 respectively