Bean White Mold

Soil-borne Sclerotinia sclerotiorum fungi
Also known as Bean White Rot

Leaf drop disease on a bean plant
Leaf drop disease on a bean plant [Credit: Rasbak]
Large sclerotia of Sclerotinia sclerotiorum
Large sclerotia of Sclerotinia sclerotiorum [Credit: Kmcleveland]
Leaf drop disease on a bean plant
Leaf drop disease on a bean plant [Credit: Rasbak]


Host Plants:

On Crops: Beans, peas, cabbage, lettuce

Where Found:

Cool temperate climates with late summer rains

Description:

Plants grow normally until rainy weather sets in just after they have become heavy with pods. Pods near the ground show cottony mold and black patches, and they are slimy rather than leathery or dry.

Damage:

As pod tissues decline from this disease, the beans become inedible. Plants may continue to grow normally. The beans inside pods often rot from this disease.

Preventing Problems:

Make sure plants get good air circulation and plenty of sun, and keep weeds controlled to promote prompt drying after rains. Use mulch to keep pods from coming into direct contact with soil. Avoid using sprinklers or other overhead irrigation methods after bean pods have formed. Plant soup beans for drying so they mature before seasonal rains begin.

Managing Outbreaks:

Gather up affected pods and compost them. Healthy plants may produce a second crop if dry weather returns in time.

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