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Billy Skaggs' Column>
Lookout for potential tomato problems
11 Jun 2007
Lookout for potential tomato problems
By: Billy Skaggs, Hall County Extension Agent
The tomato is the most commonly-grown vegetable in America’s backyard gardens. Unfortunately, producing big, red, juicy tomatoes requires considerable effort in preventing and controlling diseases.
The old adage, ‘the best offense is a good defense,’ certainly bodes true in the plant world. By selecting tomato varieties that are disease resistant, you may be able to control certain diseases before they start.
The letters behind a variety's name tell what diseases it is resistant to: T-Tobacco Mosaic Virus, V-Verticillium Wilt, F-Fusarium Wilt and N-Nematodes. Some good possibilities are Celebrity, Carnival, and Better Bush but there are many others. Resistance does not mean the plants are immune to these diseases.
The number one tomato disease now is Tomato Spotted Wilt Virus (TSWV). It is spread by thrips. Usually the top of the plant looks stunted or wilted. The young leaves may turn yellow and often have brown or black discoloration in them. The veins on the underside of leaves may thicken and turn purple. Ripe fruit will have yellow circles or semicircles.
Once tomatoes get the disease, there is no practical control. There are several varieties of tomato that are resistant to TSWV, including Capaya Hybrid. Destroy infected plants as quickly as possible early in the season to prevent spread.
Another damaging disease of tomatoes is Fusarium wilt. It clogs the water conducting tissues in the plant. The leaves yellow and wilt, often starting at the bottom of the plant. This disease can affect just one side or one to several branches of the plant. The plant can die early producing no fruit.
Control Fusarium wilt by planting resistant varieties. The 'F' after the name, like Celebrity VFN identifies these. Fusarium wilt can survive in the soil. Do not plant tomatoes in infected areas more than once every four years.
Bacterial wilt causes a rapid wilting and death of the plant. The plant dies so quickly it does not have time to yellow. To identify Bacterial wilt, cut through the stem. Bacterial wilt browns the pith or middle of the stem. On bad infections, the pith may be hollow.
To determine if your plants are affected, cut a short section of the stem and suspend it in a clear glass of water. You can often see a “milky ooze” streaming out of the bottom of the cut stem.
There are no controls or resistant varieties for bacterial wilt. It also attacks peppers, potatoes and eggplant. Carefully dig out infected plants and soil and discard. Do not plant any of these vegetables in this area for at least four years.
Southern blight is a white mold that rots the stem at or near the soil line. The plant then wilts or dies. Look for the cottony fungus growth and the light brown BB-sized fruiting structures of the fungus. The fungus may be slightly above or below the soil line. You may not see the fungus growing on infected plants when the weather is dry.
Bury all plant residues before planting and plant vegetables farther apart. Some gardeners wrap the stem near the soil line with foil to slow this disease and to control cutworms. The foil must extend two inches above and below the soil line.
Billy Skaggs
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