ABSTRACT

The utilization of cultural strategies has been proposed to suppress plant diseases caused by pathogens. In 2019 cropping session, a field trial was laid out in Randomized Complete Block Design (RCBD) to assess the incidence and severity of leaf spot disease of eggplant (Solanum gilo), to test the efficacy of crop (Zea mays) companionship and soil amendments applications on the suppression of leaf spot disease of eggplant and to ascertain the efficacy of botanicals on growth inhibition of leaf spot pathogens in Umudike, Abia State, Nigeria. The soil amendments used were Palm Bunch Biochar, Moringa Leaf Biochar, Poultry Manure Biochar, Organomineral Fertilizer (NP₂O₄ K₂O 15:4:4) and Inorganic Fertilizer (NPK 15:15:15). At two weekly intervals, 162 Kg/ha and 243 Kg/ha for fertilizers and biochar respectively were applied. The parameters considered were disease incidence, disease severity, growth, yield components and parameters. Samples of diseased leaves were taken from field to the laboratory for isolation, characterization, identification of the pathogen, pathogenicity test and pathogen inhibition. Application of soil amendments significantly (p = 0.05) suppressed leaf spot disease and promoted the yield components and yield of maize and eggplant in both intercropping and sole cropping systems. The highest infection percentage (71.34%) was recorded in control in sole cropping, while the lowest percent (8.83%) was recorded in Poultry Manure Biochar and Inorganic Fertilizer in intercropping system. The highest disease severity was recorded in control (4.34%) in sole cropping while the lowest severity was recorded in Poultry Manure Biochar (1.04%) in intercropping system. Pathogenicity reveals that the high incidence and severity of the disease is due to the complex association of several pathogens causing spot disease in Umudike. From the study, soil amendments such as application of organomineral and inorganic fertilizer as well as application of biochars significantly (p = 0.05) increased the height, number of leaves, number of branches, leaf area and fruit yield over the control in both cropping systems. It was observed that among the amendments, organic and inorganic fertilizer significantly (p = 0.05) increased yield components and yield than the biochar counterpart. Among the biochars, Poultry Manure Biochar had better plant parameters and disease conditions than Palm Bunch Biochar, Moringa Leaf Biochar and the control. The study also showed the promising potentials of intercropping in leaf spot disease suppression and suggested that the effectiveness in disease control is likely the outcome of interactions between numerous mechanisms. The studies further showed that extract of A. indica root, Z. officinale rhizome, M. olifeira root and C. papaya root have the potential (p = 0.05) to inhibit radial growth of leaf spot pathogens of eggplant in-vitro.