A study on foliage disease of Jatropha curcas was conducted in Semi–Arid region of North-Western States (Sokoto, Kebbi and Zamfara) of Nigeria to determine the incidence and severity of fungal foliar diseases. Leaves with disease symptoms were collected from the selected locations in each of the states studied and taken to pathology laboratory at Department of Crop Protection (ABU, Zaria) for identification. Curvularia and Colletotrichum species were the fungal pathogens identified and found to be responsible for leaf blight disease on the leaves of Jatropha curcas in the study area. A spore count of the isolates was made with the aid of haemocytometer and used as inocula in the pathogenicity trial in glasshouse to prove Kochs’ postulate. Results from the farmers’ field revealed that, highest incidence of Curvularia leaf blight was recorded in Tsaki of Sokoto State with 53.33% and a severity of 33.33%. Colletotrichum leaf blight on Jatropha curcas was observed to have higher incidence value of 75.67% in Janbaki of Kebbi State when compared with other States. The survey conducted showed that, Jatropha curcas planted in lowland areas tend to be more prone to the fungal leaf blight infection particularly those close to water source like streams. In the pathogenicity trial, results indicated that, there was no significant difference with respect to the methods of inoculation (smear, spray and soil inoculation). Number of days after inoculation in relation to fungal count (appearance) on leaves of the seedlings showed no statistical difference. As part of the recommendations, second field survey should be conducted in the study areas to further determine the incidence and severity of fungal leaf blight on Jatropha curcas, similarly, to enable the selection of appropriate fungicides for the control of leaf blight and pathogens responsible for the disease should be identified to species level. In vitro and In vivo evaluations of the selected fungicides should also be conducted to ascertain the most effective among them
