Vegetable Diseases to Scout for: Tomato Spotted Wilt Virus

Tomato spotted wilt virus (TSWV) has caused more problems than usual this year, particularly in high tunnel tomato. This disease can affect tomato, pepper, potato, eggplant, lettuce, beans, and cucumber along with more than 170 other plant species. TSWV may occur in the field, greenhouse, or high tunnel.  Prevention, early identification, and management will help reduce plant and yield losses.

Here are the symptoms to look for, preventative tactics, and brief suggestions on how to reduce incidence in crops once disease is confirmed.

Cause & Disease Development

Tomato spotted wilt is caused by a viral pathogen. Viral pathogens result in systemic infections, meaning that even though only certain parts of the plant may exhibit symptoms, all above and below ground portions of the plant are infected. TSWV is transmitted (vectored) by multiple species of thrips insects. When thrips feed on infected plants they acquire the virus particles, which can replicate (reproduce) within the insect. These insects can spread the virus to healthy plants when they feed. While many vegetable and ornamental plants can be infected by TSWV, a vast number of weed species are also susceptible. These weedy species can harbor the virus as well as the insect vectors.

Symptoms

Numerous symptoms can be associated with TSWV, and symptoms can vary depending on the plant species. Common symptoms include ringspots on leaves (Figure 1), stem lesions, leaf bronzing, stunting, and wilting. Fruit may also exhibit symptoms such as mottling (inconsistent color), ringspots, and irregular growth (Figures 2 & 3). In particular, these symptoms will be most apparent in “sink” plant tissues, which are the youngest leaves, blossoms, and fruit. Symptoms of TSWV can often be confused with damage from other abiotic issues. If TSWV is suspected, it is recommended growers submit a plant sample to their county Extension agent; however, the agent may choose to forward the sample to a University of Kentucky Plant Disease Diagnostic Laboratory for analysis and disease confirmation.

Figure 1: TSWV infected plants may exhibit symptoms such as ringspots on leaves. (Photo: Paul Bachi, UK)

Figure 1: TSWV infected plants may exhibit symptoms such as ringspots on leaves. (Photo: Paul Bachi, UK)

Figure 2: Ringspots developing on immature tomato fruit from TSWV infected plant. (Photo: Emily Pfeufer, UK)

Figure 2: Ringspots developing on immature tomato fruit from TSWV infected plant. (Photo: Emily Pfeufer, UK)

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Figure 3: Fruit of TSWV infected plants may show mottling, ringspots, and/or irregular growth. (Photo: Paul Bachi, UK)

Figure 3: Fruit of TSWV infected plants may show mottling, ringspots, and/or irregular growth. (Photo: Paul Bachi, UK)

Management

If plants are confirmed to be infected with TSWV, no management strategies are available to improve individual plant health. Preventing infection of asymptomatic plants is the most important management technique for TSWV.

Cultural practices

  • Select disease resistant varieties.
  • Do not set transplants that have visible spots.
  • Utilize reflective mulches to deter thrips.
  • Remove all above- and below-ground portions of infected plants; destroy to reduce disease spread.
  • Manage weeds aggressively, both within and in close proximity to production areas.
  • Manage thrips insect vectors.

Chemical approaches

No chemical management options are available for plants infected with TSWV. However, insect management options to reduce disease spread include chemical management. For more information on chemical management options for thrips, please consult a county Extension agent and ID-36.

Resources

  • Home Vegetable Gardening (ID-128)
  • IPM Scouting Guide for Common Problems of High Tunnel and Greenhouse Crops in Kentucky (ID-235)
  • IPM Scouting Guide for Common Problems of Solanaceous Crops in Kentucky (ID-172)
  • Sustainable Disease Management of Solanaceous Crops in the Home Garden (PPFS-VG-21)
  • Tomato Spotted Wilt Virus Fact Sheet (Cornell University, October 1989, Fact Sheet Page 735.90)
  • Vegetable Production Guide for Commercial Growers (ID-36)

 

By: Kim Leonberger, Extension Associate and Emily Pfeufer, Extension Plant Pathologist

 

Posted in Vegetables