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White Mold potato disease

Thursday, September 10th, 2009

(Sclerotinia sclerotiorum)
White mold disease affects potato mainly in the cool tropics and temperate zones. But it causes major damage to potato when the rotation includes susceptible vegetable crops (beans, lettuce, tomato, celery, cauliflower, cabbage). It is favoured by cool, moist weather.

Symptoms of White mold

Stem lesions develop at the soil line or near leaf axils and are slightly sunken, oval, or elongated, extending up the stem. Initially, lesions are water-soaked, later becoming tan colored, white at the center, and ringed or zonate.

white-moldAffected stems are covered with a white mycelial mat.
The central pith is destroyed and the hollow becomes filled with white mycelium that later forms hard, black, 0.5 to 1.0-cmlong sclerotia.
Tops may wilt and stalks split or break at the soil surface.
Potato tubers near the soil surface become shrunken, superficially blackened, and watery.
Cavities lined with black dead tissue later fill with white mycelium and sclerotia.

Sclerotia germinate, forming mycelial mats or small, fleshy, cup-shaped mushrooms from which air-borne spores disseminate and infect the leaves and stems of many dicotyledonous crops and weeds.

Management

The long-lived sclerotia can be killed by flooding for about 5 weeks. Rotations with non susceptible crops, including potato only every third year, along with removal and destruction of infected plants, help reduce this disease while potatoes growing. Avoid overhead irrigation.

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One Response to “White Mold potato disease”

  1. […] White mold symptoms first appear as water soaked lesions 14 to 20 days following row closure. Lesions usually first appear in the intersections between the stem and branches, or on branches and stems in contact with the soil. These become quickly covered with a white cottony growth that can spread rapidly to nearby stems and leaves if moisture is present for several hours. As lesions expand they can girdle stems causing foliage to wilt. White mold is also often accompanied by bacterial stem rot, especially under wet conditions. […]

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