Assessment of leaf blight on Colocasia esculenta and in vitro effect of three medicinal plants extracts on leaf blight disease pathogen in Oshie-Njikwa, North West Region-Cameroon

Abstract

Taro (Colocasia esculenta) is a major staple food in Cameroon. This work assessed leaf blight disease on Colocasia esculenta and in vitro  effect of three medicinal plants extracts on the pathogen in Oshie. Questionnaires were administered to 200 randomly selected farmers  to assess the impact of the disease. Eight farms in Oshie were surveyed for leaf blight disease during a period of six weeks for disease  incidence and severity. Twenty diseased leaf samples were collected, inoculated on Potato Dextrose Agar and after 7 days of incubation,  pure cultures were identified. Crude extracts of hexane and methanol from leaves of Clematis hirsuta, Clematopsis scabiosifolia and  Telferia occidentalis were evaluated for in vitro antifungal activities on Phytophthora colocasiae. Leaf blight disease of taro had a huge  impact on farmers as it reduced yield of the tubers. Disease incidence ranged between 15% and 99%. Disease severity ranged from  46.24% to 61.82%. All three plants extract at 0.5 g/ml concentration had inhibitory activities on the test fungus. The three plants extracts obtained using methanol inhibited the growth of Phytopthora colocasiae more than the same three plants extracts obtained using  hexane. The three medicinal plants can be used to control taro leaf blight in vitro.