Halo blight

Pseudomonas syringae pv. phaseolicola

Halo blight affects the foliage and pods of the common bean, lima bean, and soybean. The first symptoms are small, water-soaked lesions resembling pinpricks on the underside of leaves. The small lesions rapidly turn dry and reddish-brown, and are visible on both sides of the leaf. These lesions usually remain small. A greenish-yellow zone of irregular shape and size, resembling a halo, often develops around the reddish-brown lesions. At high temperatures, the halo may be small or absent. Infections can become systemic, that is, spread throughout the plant, leading to yellowing and death of new foliage. Pod symptoms begin as tiny, water-soaked spots on the pod surface that gradually enlarge to form dark, sunken lesions. A cream-colored to silver bacterial ooze is often associated with pod lesions, and seeds in infected pods can be discolored, shriveled, and small.

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