Rice false smut and its management in major rice growing areas in Ashanti region of Ghana

Ustilaginoidea virens, the pathogen that causes rice false smut (RFS) disease induces infertility in infected spikelets, reduces grain weight and caused up to 75% yield loss. Surveys on RFS disease were conducted from September to December, 2015 in 60 rice farms within three districts: Ejisu-Juaben, Ejura-Sekyedumase and Asante Akim-North, in the Ashanti region of Ghana. Incidence and severity, as well as farmers’ perception of the disease were obtained using questionnaires. Symptomatic rice panicles were collected from farms for identification of associated pathogen in the laboratory. Effect of four inorganic fungicides: Mancozan super, Suncozeb, Nordox and Sidalco Defender on mycelial growth and sporulation of the RFS pathogen were studied using the food poisoning method. Fourteen rice varieties were evaluated for their response to the disease. The surveys revealed that most (60%) of the farmers had no knowledge of the disease. The highest incidence of RFS disease was observed at Duampompo (23.3%) in Ejisu-Juaben Municipal/District, Ntemaso (23.3%) in Ejura-Sekyedumase District, and Habitat (38.0%) in Asante-Akim North District. The highest severity was observed at Ntemaso (5.0) in Ejura- Sekyedumase and Habitat (7.6) in Asante-Akim North District, with Bomfa recording the highest severity (5.0) in the Ejisu-Juaben Municipal. U. virens was isolated from diseased rice samples collected from the surveyed fields. The four fungicides evaluated exhibited 100% inhibition on the growth of U. virens mycelium eight days after inoculation in vitro however, Nordox was the most efficient after 23 days inoculation and the Mancozan super was the least efficient. Evaluation on rice varieties response to U. virens should be repeated and the effectiveness of fungicides should be tested under the field-infected plants in order to sustain the present results.   Key words: Ustilaginoidea virens, rice false smut, disease.