Halo blight and common blight reduce dry bean yields by reducing the ability of leaves to photosynthesize. Tips Host Crops Dry beans Biology Hail, blowing sand, or wind-whipping, followed by rain, often trigger bacterial blights. Bacterial blights are also spread if bean rows are cultivated while leaves are wet. The most common bacterial diseases are halo blight and common blight. Halo blight may occur any time during the cropping season.
Typical symptoms are small brown spots that are surrounded by a light-green or yellow halo.
The halo ranges from dime-size to the size of a quarter. In hot weather, halo blight will resemble bacterial brown spot. Both diseases are carried on the seed and can be spread from plant to plant by rain, hail, irrigation, or wind. In the soil, blight can survive in old, diseased plants for a year or longer. The dead areas enlarge rapidly under favourable conditions until they cover most of the leaf, giving the plants a burned appearance.