Mature spots are circular to oval and sunken. Use western grown certified seed to minimize disease. Do not work in garden when plants are wet. Use a three-year rotation. Remove residue after harvest.
Leaves have irregular watery light green patches.
Pods have small, water-soaked spots that enlarge to irregular blotches. Later become brown, dry and sunken areas. Use western grown certified seed. Do not work in garden when plants are wet. Spray copper fungicides at weekly intervals.