Tomato (Solanum lycopersicum)-Tomato Spotted Wilt

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Cause The Tomato spotted wilt virus, which is transmitted from plant to plant by thrips (an insect). This and the closely related Impatiens necrotic spot virus can infect hundreds of weed, ornamental, and vegetable species, which then can harbor the virus. In Oregon, the problem is primarily in greenhouse tomatoes but has been found also in home gardens. Seed transmission has been reported in tomato.

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. Pale green or white fruit blotches or spots develop on green fruit. Maturing fruit has yellow, orange, or green spots, blotches, or concentric lines. Ring spots or black spots also may be present. Severely affected plants may form no fruit at all, or fruit may be small and unmarketable. Diseased plants do not yield well.

Cultural control

  • Greenhouse production.
    • Do not grow vegetable transplants in greenhouses that contain or recently contained ornamentals, especially if they were infected with TSWV.
    • Prevent thrips from entering and monitor for them.
    • Destroy infected plants. Do not leave cull piles.
    • Keep the greenhouse free of weeds, which may be virus reservoirs.
  • Commercial field production.
    • Do not accept or plant transplants that have ring spots or bronze to purple flecks on leaves.
    • Do not plant next to greenhouses in which herbaceous ornamentals are grown.
    • Plant on UV-reflective mulch.
  • Home gardens.
    • Inspect plants for disease symptoms. Plant only pathogen-free transplants.
    • Destroy any infected plants that appear in the garden.
    • 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.