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Tomato (Lycopersicon esculentum) - Tomato Spotted Wilt
Cause The tomato spotted wilt virus, which is transmitted from plant to plant by thrips. This virus is a primary problem in greenhouses and can infect hundreds of weed, ornamental, and vegetable species, which then can harbor the virus. In Oregon, the problem has been found in potato fields.
Symptoms Symptom severity depends on when plants are infected. Plants infected young may be severely stunted with irregular leaf shapes, necrotic young leaves, and an unthrifty appearance. Plants infected when older may show stunting but will have leaves that develop bronze or purplish irregular markings on the leaflets' upper sides. Markings may include flecking or ringspots. Leaf distortion, leaf yellowing, dark purple stem streaks, tip dieback, or wilt also may occur. Severely affected plants may have severe defoliation that resembles late blight.
Cultural control
- Use certified seed potatoes.
- Do not plant next to greenhouses in which herbaceous ornamentals are grown.
- Rogue out infected plants.
- Plant on UV-reflective mulch.
Chemical control None, once plants are infected. However, greenhouse operations should control the thrips vector to prevent disease spread. Thrips control is more difficult in field situations.