This fungal disease appears as circular, dark, sunken spots on pods and stems. The fungus overwinters in the seed and in bean refuse. Spores are scattered from plant to plant by wind, rain, and people working in the garden, especially when the foliage is wet. To control, use disease-free seed and allow two years rotation between bean plantings. Rust Bean rust is a disease chiefly of the leaves.
Symptoms appear as powdery red or black pustules about the size of pinheads.
High humidity favors development of this disease. Rust is only a problem in the late summer and fall. Plant-resistant varieties are one solution. Root Rot Root rot fungi survive in the soil from year to year, so rotation is very important. Most root rot fungi are favored by cool weather and high soil moisture content.