Tomato Spotted Wilt

Tomato spotted wilt is a viral disease spread by thrips.

Tomato spotted wilt (Scot Nelson) Public Domain

Besides tomatoes, this virus can be found on chili peppers, eggplant, lettuces, radicchio, and fava beans, along with many ornamentals and weeds. Cheeseweed, sowthistle, bindweed, and prickly lettuce are the most common weed hosts.

Pepper infected with spotted tomato virus (Carlos Gonzalez) CC BY-SA 3.0

Tomato spotted wilt symptoms

When the tomato spotted wilt virus infects a plant, it blocks the flow of water and nutrients in the xylem, causing it to wilt. This viral disease also causes spotting, stunted growth, a crumpled leaf appearance, leaf cupping, dead spots (necrosis) on leaves and stems, and overall discoloration.

Sweet basil infected with tomato spotted wilt (Scot Nelson) Public Domain

Symptoms can vary, depending on the plant’s overall health, the cultivar, environmental factors, and life stage at the time of infection:

• Infected seedlings end up severely stunted at what should have been their transplant stage.
• Leaf bronzing and petiole necrosis are common symptoms of plants infected during their vegetative stage.
• When infection occurs at the flowering or fruiting stages, fewer shoots develop, leaves curl and may have yellow or purplish discoloration. 
• Fruits are bumpy, deformed, and have visible ringspots.

This disease is easily mistaken for curly top and alfalfa mosaic virus. You can take samples to your County Extension Office, though the control measures are rather similar for all three diseases.


How tomato spotted wilt spreads

Tomato spotted wilt is spread by thrips. Most commonly, in California, it is citrus thrips and western flower thrips. These sap-sucking pests carry the virus with them. As they feed, they insert the virus.


Tomato spotted wilt control
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It is far easier to prevent tomato spotted wilt than break this particular disease triangle. These tips can help reduce the chance of it occurring in your foodscape:

• Plant resistant varieties.
• Quarantine plants until you are certain they are virus- and thrip-free.
• Monitor plants closely for thrips to prevent spreading the disease.
• Control thrips.
• Remove nearby weeds.
• Remove and compost exhausted tomato plants after harvest.
• Remove diseased plants and throw them in the trash.

May you never find tomato spotted wilt in your garden!