Feature
June
09
Tomato Spotted Wilt Virus
by Barton Joffrion, County Agent, LSU AgCenter
Why plant new and different tomato varieties?
Home vegetable gardeners like to have fresh vine-ripe tomatoes, and when they find one they really like, they usually plant it year after year. One such example has been the Celebrity variety, a well-producing tomato that usually finishes among the top three in most taste tests.
The problem over the past several years is that it has been affected by a disease called tomato spotted wilt virus. Insects called thrips transmit the virus. Juvenile thrips acquire the virus from an infected weed host and disperse it after becoming winged adults. Potential host virus carriers include spiny amaranthus, wild lettuce, pasture buttercups, Solanum and sowthistle. These are all abundant in the state when tomatoes are in the field.
The virus causes multiple symptoms. On young, rapidly growing plants, the spotted foliage is typical. This causes internal black splotchy spots on the leaves. They are not dead, or necrotic. The top may take on an off-color and may or may not curl.
Later, the older plants that have slowed down their growth spurt will stunt, the leaves will roll and the plant will be off-color. Symptoms on ripening fruit are large orange-to-yellow circles inside the tissue. These are larger than stink bug damage, which also yellows the fruit at the point of insect insertion. Often, the veins of the leaves turn purple, especially in the older plants. You must rogue out infected plants because there are no sprays to correct the virus after it affects the plant.
With that said, this is why the question was posed at the beginning of this article. Seed companies, commercial growers and extension specialists and agents have been planting TSWV-resistant tomato selections over the past several years. Keep in mind that the varieties may still get TSWV; however, they are not as susceptible to the virus.
For home gardeners who plant about 10 to 20 plants, it is a good idea to plant two to three varieties that are listed as TSWV so they don’t all have one variety that could become infected and make very few tomatoes.
The La-Terre Master Gardeners have planted some varieties that will be discussed at the Vegetable Field Day on June 11 at the USDA Sugarcane Research Facility across from Chauvin Funeral Home in Houma. The event will be a chance to see the virus out in the field and to ask questions about growing tomatoes and other vegetables. LSU AgCenter specialists, agents and master gardeners will be out there to answer questions about your garden.
