The warm weather this year has vegetable gardens producing earlier than normal. One day this past week, I heard one gardener already talking about harvesting tomatoes.
The tomato is the most commonly grown vegetable in gardens. Gardeners will grow tomatoes if they don’t grow anything else. Tomatoes are easy to grow, and everyone who grows them has their special way, but there are some problems that affect tomatoes.
Disease problems can be reduced by following a few simple rules. The first rule is to buy disease-resistant plants. 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. Resistance, though, does not mean the plants are immune.
The second rule is to practice rotational planting. Don’t plant tomatoes where tomatoes, potatoes, eggplant or peppers were planted last year. Soils in these areas may harbor leftover diseases. Bury all plant debris when tilling. By burying old plant debris 6 inches deep, disease organisms can be kept away from the plants. Also, mulches should be pulled back an inch or two from the stem of the plants.
Even if you do everything right when it comes to disease prevention, tomatoes can still get disease. The most common tomato disease now is Tomato Spotted Wilt Virus (TSWV). Most of the viruses that cause disease problems are spread by insects, such as aphids, whiteflies, plant hoppers or thrips. TSWV is spread by thrips. When a plant has TSWV, the top looks stunted or wilted, and the young leaves may turn yellow and often have brown or black discoloration. The veins on the underside of leaves may thicken and turn purple. The fruit can have circles on them that are raised or flat. Ripe fruit will have yellow circles or semicircles. The stem can have long brown lesions.
Once tomatoes get the disease, there is no control. There are two varieties of tomato that are resistant to TSWV. They have been on the market for five years. I grow them in my garden, and have had good success. The skin of these tomatoes is a little thicker than other varieties. The flavor is good, and is best if the fruit is left on the plant as long as possible before picking.
If there are plants that show signs of TSWV, destroy them as quickly as possible early in the season to prevent spreading the thrips. Seal them in a plastic bag. Even after the plant is pulled up, thrips can leave the plant to spread the virus. If the tomato gets TSWV late in the season, let the infected plants finish ripening the fruit they have. Late-season infection is less of a concern.
The next problem that I am getting some calls on is bacterial wilt. Bacterial wilt causes a rapid wilting and death of the plant. The plant dies so quickly it does not have time to yellow. Most callers say that the plant looked good one day and looked like someone poured boiling water on it the next. An easy way to identify bacterial wilt is to cut through the stem of the tomato and look at the center. Bacterial wilt browns the middle of the stem. On bad infections, the pith may be hollow.
Unfortunately, there are no controls or resistant varieties for bacterial wilt.
This disease will also attack peppers, potatoes and eggplant. If bacterial wilt is a prolem, dig out infected plants and soil and discard. Make sure the discarded soil is not in an area where you will plant vegetables in the future. Do not plant tomatoes, peppers, potatoes or eggplant there for at least four years.
Another concern of tomato growers is rolling of the plants leaves.
Leafrolling occurs when the plant has set a heavy load of fruit and the light intensity is high, or it can be caused by wet soil. Some varieties of tomatoes will roll their leaves more than others. The condition is harmless. However, there is a virus that can cause this problem. The only way to tell if this is a virus is to look at the fruit, which will be misshapen or have dark spots on it.