Anthracnose (Glomerella lindemuthiana)
Small, dark brown to black lesions on cotyledons and lesions on stem occurs which appear to be sunken. Lesions also occur on the pods which are brown to purple in colour and appear to be sunken. When germination of infected seeds takes place, lesions develop of cotyledons and the spores can be spread by insects, humans or cultivars. It can be controlled by using pathogen free seeds. It can be effectively controlled by crop rotation . The disease can be controlled by spraying foliar sprays like Mancozeb at 2g/lit or Carbendazim at 1g/lit or Chlorothalonil at 2g/lit.
Halo Blight (Pseudomonas syringae pv. phaseolicola)
Caused by a seedborne pathogen. It forms small, angular and water soaked spots on the lower leaf surface and forms a halo of yellow tissue which develops around each water soaked spot. On pods, the water soaked spots many become slightly sunken and reddish brown with age. In order to prevent occurrence of this disease, deep ploughing and pathogen free seeds are required. The seeds can be treated with streptomycin and can be curbed by spraying copper containing chemicals every 7 to 10 days on the infected plants.
Bacterial Blight (Xanthomonas campestris or Xanthomonas axonopodis)
Leads to formation of water soaked spots on leaves which enlarge and become necrotic. The lesions coalesce and give the plant burned appearance. On pods circular, sunken and red brown lesion are formed on the pods. This disease can be caused by contaminated seed, wet weather conditions etc. This organism is commonly seedborne and as the germination occurs, bacteria contaminate the surface of the cotyledon and spread to leaves finally spreading across the vascular system. It can be controlled by crop rotation and deep ploughing can also eliminate infested bean debris in field. It can also be treated with copper based fungicide such as Kocide 101.
Bacterial Brown Spot (Pseudomonas syringae)
Causes small oval, necrotic lesions on leaves. The leaf tissue around the lesion may appear puckered and they may coalesce and their centers fall out, giving leaves tattered appearance. Small lesions also appear on pods. It can be curbed by crop rotation and spraying of the plants with copper containing chemicals weekly.