Fungitoxic Screening of Some Local Plant Extracts for the Control and Yield Performance of Cowpea (Vigna unguiculata L Wasp) Infested with Anthracnose Disease in Southeastern Nigeria

Field experiments were conducted in late 2013 and 2014 cowpea cropping seasons in 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 cowpeas induced by Collectotrichum lindermuthianum and to assess the yield performance of the crop. 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. Seeds of cowpea (Ife Brown) disinfected and inoculated with spores of Colletotrichum lindemuthiamum were used for the study. The field trial was a three factor experiment, (leaf extracts, seed inoculation and seed disinfection) designed in randomized complete block design and replicated three times. Cowpea was spaced at 0.5 m x 0.75 m and sown in plots measuring 3 m x 3 m. Data were collected fortnightly for yield traits performance such as 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 Software for Analysis of Variance (ANOVA) and the Fisher’s LSD mean separation. Results of data analysis showed that significant (P<0.05) differences existed among the leave extracts used as treatments. Results on disease development showed that disease incidences of anthracnose recorded for cowpea were 71.03% and 18.06% for control and C. odorata treated plots respectively. The disease severity indices of 7.17 and 0.59 were recorded for the control and A. occidentale extract sprayed plots, respectively. Results on yield traits performance showed significant (P<0.05) differences in the effect of the different plant extracts evaluated. Highest grain yield of 68.18 kg/plot was recorded on Anacardium occidentale extract treated plots. Number of seeds per pod was 11.17 for Chromoleana odorata with higher yield loss of 66.99% in the control plot. Plots sprayed with benomyl yield loss were 22.39%, while plots sprayed with A. occidentale yield loss was 31.83%. Plots sprayed with leaf extracts of C. odorata recorded yield losses of 42.81%. Percent yield of cowpea was 43.24% in plots sprayed with leaf extracts of G. arborea. The order of efficacy of leave extracts was Benomyl > Anacardium occidentale > Chromoleana odorata > Gmelina arborea > Control. Hence, it is recommended that farmers should use leaf extracts of Anacardium occidentale to reduce yield losses from anthracnose infested cowpea and for high yield performance and control of cowpea Anthracnose disease in South Eastern Nigeria.