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Posts Tagged ‘symproms’

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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Wart potato disease

Thursday, September 10th, 2009

(Synchytrium endobioticum)

Wart is potatoes disease caused by Fungi.

Wart or black wart is widely distributed in temperate and high altitude tropical regions with cold and rainy climates. It may cause considerable yield loss where races of the fungus occur for which resistance has not been introduced. The disease is often associated with powdery scab and does not develop in warm or dry soils.

Symptoms of Wart

Tumors of any size up to several centimetres may develop on stems, stolons, and tubers.

Symptoms usually develop below-ground, but under wet conditions they may appear on stems and foliage. Initially, tumors are white to brownish or of the same colour as normal tissue. Tumors blacken with age and may rot because of secondary organisms. Aboveground warts are green, reddish, or purple, depending on variety.

Management

Varieties that are resistant to races of the fungus should be used. Reduce wart incidence with long crop rotations (5 years or more) in combination with resistant varieties.

Prohibiting the shipment of tubers, particularly seed from infested regions, is effective in limiting disease spread.

Seed of resistant varieties grown in infested soil can spread the disease as well as movement of infested soil or manure adhering to tuber surfaces, farm machinery, or other equipment.

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