Pathogen identification and chemical control of brown leaf spot disease of rice caused by Bipolaris oryzae

Abstract

Brown spot disease destroys rice plants in the field. While symptoms of the disease have been observed in the irrigated rice producing areas of Ghana, information about its importance and etiological agent is scant. In this study, field surveys were carried out in 11 major districts, where irrigated rice is grown in Ghana and the disease incidence and severity were determined. The causal agent was isolated and identified, using its cultural and morphological characters, complemented with the sequence analysis of the internal transcribed spacer region and the glyceraldehyde-3-phosphate dehydrogenase gene. After that six different types of fungicides were evaluated against the disease in the field. The disease prevalence 100% in the study area, with disease incidence ranging from 86.7% to 100% and severity ranging from 24.67 to 57.61%, among the districts surveyed in 2 successive years. The fungus B. oryzae was confirmed as the causal agent of the disease. Copper based fungicides (Cuprofix disperss, Coprous super and Curenox), botanicals (Ex-icute and Supramino 999) and an inorganic fungicide (Mirage), controlled the disease, and increased yield of rice. It is therefore recommended that copper-based fungicides can be rotated with organic fungicides to control the brown spot disease of rice in Ghana.