Diseases Primarily of Beans

Common blight (Xanthomonas phaseoli)

Common blight, a bacterial disease occurring on almost all beans, spreads most rapidly when temperatures are warm and humidity is high. Beginning as a spot on the plant tissue, lesions expand to destroy leaflets and pods. Controls for common blight include disease-free seed, a 2-to-3-year rotation, and good sanitation.

Rust (Uromyces phasioli)

Rust, a fungal disease of snap beans, lima beans and scarlet runner beans, can destroy the entire crop when relative humidities are over 75 percent with temperatures of 63 to 81 degrees F. Pustules, formed on all above-ground plant parts, are initially white, later becoming a characteristic reddish-brown and circular. In severe epidemics, leaves fall off.

Crop rotations of three years or longer and burial of plant debris will help control rust. Cultivars resistant to specific races of rust are available, although no cultivars are resistant to all races. Fungicides are effective if applied early in the infection.

Stem anthracnose (Colletotrichum truncatum)

Stem anthracnose, a fungal disease, and the most common disease of lima beans, is the factor limiting lima bean production in southern Georgia. Brick red spots appear on the pods and the whole plant may be infected. Anthracnose overwinters on plant debris and may be seedborne. Control measures include: using clean seed, planting in well drained soil, and a 3-year crop rotation.