Mapping of Angular Leaf Spot Disease Hotspot Areas in Western Kenya Towards Its Management

Abstract

Common bean (Phaseolus vulgaris L.) is an important crop in the daily diet of more than 300 million people worldwide. Despite its importance, bean productivity is declining in western Kenya due to diseases and use of low yielding susceptible varieties. Among the diseases, ALS is a major biotic constraint of bean production in western Kenya. It causes an estimated yield loss of about 80% in the farmers’ field when severe. There is still limited information on pathogen distribution in western Kenya hindering breeding for ALS resistance. Therefore, a study was conducted to determine the occurrence of ALS disease in bean growing areas of western Kenya. A disease survey was carried out during the long and short rains seasons of 2013 in six agro-ecological zones namely: Low midland zone 1 (LM1) (Rongo and Bumula), low midland zone 2 (LM2) (Busia, Bungoma and Rangwe), low midland zone 3 (LM3) (Siaya and Teso north), low midland zone 4 (LM4) (Bondo), lower highlands (LH1) (Nandi Central) and upper midland zone 1 (UM1) (Sabatia and Nandi south). UM1 recorded the highest disease incidence and severity, whereas LM4 registered the least. Similarly, there was a significant positive correlation between disease incidence and severity (r = 0.711; p<0.0001). The study found the incidence and severity levels of ALS in western Kenya as high as 100% and 3 respectively. Therefore, farmers should be encouraged to use certified seeds to minimise the severity of the disease.