IN VITRO ACTIVITY OF SYNTHETIC FUNGICIDES AND SOYBEAN EXTRACT ON COLLETOTRICHUM GLOEOSPORIOIDES, CAUSAL PATHOGEN OF ANTHRACNOSE DISEASE OF CASHEW IN GHANA

Anthracnose disease caused by Colletotrichum gloeosporioides complex, is one of the most important diseases of cashew (Anacardium occidentale) in Ghana and other African countries. It affects the quantity and quality of cashew nuts leading to economic loss to farmers. Chemical control using synthetic fungicides is a major approach in controlling the disease although knowledge on the efficacy of several synthetic fungicides and botanicals against the causative pathogen is limited. In this study, the bioactivity of soybean extract and nine synthetic fungicides were evaluated against five isolates of Colletotrichum gloeosporioides complex on amended agar plates for 3, 5 and 7 days. The fungicides tested were CUPH (77% Cupric hydroxide), MMCO (60% Copper oxide + 6% Metalaxyl-M), PYDM (7.2% Dimethomorph + 4% Pyraclostrobin), DMFL (Dimethomorph 200 g/L + Fluazinam 200 g/L), MECO (15% Metalaxyl + 35% Copper), CUHY (53.8% Copper hydroxide), CUPO (86% Cuprous oxide), CUOX(435 g/L Copper oxychloride) and FLUA (500 g/L Fluazinam). The percentage growth inhibition (PGI) of the isolates in plates amended with the soybean extract ranged from 3.73% to 81.74%, 4.46% to 80.38% and 2.53% to 76.63% after 7, 5 and 3 days of incubation respectively. With the synthetic fungicides, the PGI of the isolates ranged from 54.08% to 100%, 53.04% to 100% and 59.87% to 100% after 7, 5 and 3 days respectively. However, fungicide MMCO inhibited completely all the C. gloeosporioides isolates at all the incubation days. This study shows the efficacy of synthetic fungicides in the control of anthracnose disease of cashew as well as soybean extract as a potential bio-fungicide. The bioactive compounds present in the soybean extract, once identified and formulated for field application offers potential active ingredients for the control of anthracnose disease of cashew.