The problems, solutions with tomato spotted wilt

Tomato spotted wilt (TSW) is the No. 1 disease of tomatoes that we encounter these days. It can also affect peppers, celery, eggplant, peanuts, lettuce, pineapple, many legumes, and many ornamentals. TSW is caused by a virus spread by two species of thrips, tiny insects with scraping and rasping mouthparts. Thrips carry the wilt virus from various host plants (weeds) and can transmit the virus within minutes of active feeding.

Symptoms of TSW include stunting of the tomato plant, drastically reducing yields and causing irregular ripening and yellowing of tomato fruit. Leaves may turn yellow and have red, brown, or black discolorations, forming a ring. Veins on the undersides of affected leaves may turn purple and thicken. If the fruit are set before infection, they may be distorted or develop blotchy orange ring spots as they ripen.

If you have a history of problems with TSW in your garden, be aware that you are more likely to have disease pressure due to the presence of infected weeds in the landscape. Weed hosts identified as potential virus carriers include spiny amaranthus, wild lettuce, pasture buttercup, curly dock, sowthistle, lambsquarters, chickweed, clover, jimsonweed, morningglory, pigweed, among others.

Once tomatoes are infected with TSW, there is no control. Spraying for the culprit thrip is not effective once the damage is done. The best approach to controlling the TSW is the use of resistant varieties. Tomato varieties that have confirmed resistance to this virus include Amelia, Quincy, BHN 640, Crista, Bella Rosa, Talladega, Red Defender, BHN 444, Redline, BHN 602, Top Gun, Mountain Glory, Fletcher, Finishline, Tribute, and others. Most of these are commercial varieties, but some may be available to the home gardener. Commonly grown varieties such as Better Boy, Big Boy, Beefsteak, Beefmaster, Big Beef, Early Girl, Goliath, etc. offer no known resistance to the virus.

Resistant bell pepper cultivars include Declaration, Excursion II, Heritage, Stilleto and Plato.

Perhaps the best non-chemical approach for reducing thrips is the use of metallic-reflective mulch. This mulch serves to disorient and therefore discourage the thrip from feeding on the tomato plants.

To summarize, while the elimination of TSW may not be possible, the incidence and severity of the disease may be reduced by using cultural practices such as starting with virus-free and virus-resistant plant material, removing all infected plants (once virused, there is no cure for the diseased plant), controlling weeds, rotating crops, and the use of reflective mulches under plants.

I trust you will have a long and prosperous gardening season free of the dreaded tomato spotted wilt virus.

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