Bacterial Leaf Blight
The infection can occur at any growth stage. The symptoms differ slightly depending on the plant age. Seedlings with injured growing tips and angular water-soaked spots on primary leaves and stems develop from infected seeds. The plants show a characteristic wilt during the day. If the infection occurs during later growth stages, the leaves show small, water-soaked spots with lemon-yellow margins. Over time, they grow into brown, necrotic lesions that give the plant a burnt appearance. This might result in defoliation. Infected plants remain dwarf and produce few pods with reddish-brown or brick-red lesions. The stem develops reddish streaks. It often splits and releases a yellowish exudate. If the infection occurs during pod development, the seeds may appear shriveled, shrunken, rotten or discolored.
The bacteria Xanthomonas phaseoli remain dormant for several years in the soil, seed coat, alternative hosts and on plant debris. Rainy, wet and warm weather conditions (25-35°C) and humidity favor the occurrence. The disease is heavily spread through wind driven rain, rain splashes and insects (grasshoppers and bean beetles). Natural openings and wounds on plants also favor the occurrence.
Sorry, we don't know of any alternative treatment against Xanthomonas phaseoli . Please get in touch with us in case you know of something that might help to fight this disease. Looking forward hearing from you.
Always consider an integrated approach with preventive measures together with biological treatments if available. Chemical treatment of the disease may be inviable because the bacteria might develop resistance in the long term. If bactericides are needed, products containing copper and streptomycin (antibiotic) should be applied as seed and foliar treatments.