Tomato diseases caused by Phytophthora pathogens: 1. Buckeye Rot occurs on fruits that are in contact with the soil. The disease begins as small brown spots on fruit which grow in to large, round or oblong lesions with alternating concentric rings of light and dark brown discoloration. The lesions are firm, with smooth margins; but eventually become soft and decayed. Buckeye Rot is most prevalent during warm, wet weather and is spread by surface water and splashing rains. Excess soil moisture favors infection. • Avoid fields with heavy, poorly drained soils. • Reduce soil compaction. • Plant in raised beds. • Avoid low areas of fields. • Rotate to non-solanaceous crops. • Stake and/or mulch plants to reduce contact with soil. 2. Late Blight spreads easily on wind and rain and is capable of destroying entire fields in a few days. Late blight is extremely destructive when not managed, quickly killing foliage and infecting tomatoes and potatoes. The most common symptoms on tomatoes are sunken, dark green or brown lesions on leaves and brown lesions on stems, with white fungal growth developing under moist conditions and quickly growing bigger. Chose resistant verieties and start with healthy seedlings. Monitor tomato and potato crops on a regular basis, especially wet areas and whenever wet weather occurs. Remove and distroy infected plants immediately. Avoid diseased plant material touching the ground. Remove the soil where a diseased plant was growing and replace with healthy soil. Practice crop rotation with non-solanaceous crops. Desinfect hands and tools to avoid spread of the disease. Protective fungicide application might be necessary inlate blight prone areas. 3. Phytophthora crown rot: Prevention is the key to managing Phytophthera crown rot as it is difficult to suppress with fungicides once it develops. Fields free of it will remain so unless contaminated with infected equipment or clods of soil or contaminated irrigation water but it is very difficult to detect Phytophthora in irrigation water. The pathogen is not likely to be seed-borne in commercial seed, and it does not travel easily through the air for long distances. It develops when the soil is saturated with water for several hours and temperatures are high. It causes a root and crown rot and produces distinctive black lesions on stems. Root infection leads to wilt and eventual death of plants. The pathogen also infects leaves causing water-soaked, circular, brown lesions. Leaf and stem lesions often result from splash dispersal of the pathogen onto the lower portions of the plants. Fruit can also be infected resulting in lesions similar to leaf lesions. In high humidity, lesions may be covered with white sporangia.
Posted on: Thu, 11 Dec 2014 09:26:50 +0000
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