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Combating Common Tomato Problems

While tomatoes might be the number one vegetable we grow, they are certainly the number one vegetable we get questions about. Tomatoes can be difficult to grow! Let’s dive into some of the common issues I am seeing or have seen in the past!

Tomato Spotted Wilt Virus (TSWV) is a common disease that is spread by thrips. The top of the plant will look stunted or wilted. The young leaves may yellow and often have brown or black discolorations. The veins on the underside of leaves may thicken and turn purple. Fruit can have raised or flat rings or circles on them. Ripe fruit will have yellow circles or semicircles.

Once tomatoes get the disease, there is no control. A few varieties of tomato are resistant to TSWV including Amelia, Stiletto and others. The variety must specifically say it is resistant to Tomato Spotted Wilt. Pull, seal up in a bag and discard or destroy infected plants as quickly as possible early in the season to prevent disease spread. Even after the plant is pulled up, thrips can spread the virus. Late in the season, let the infected plants finish ripening the fruit they have.

Fusarium Wilt is caused by a fungus that blocks the water conducting tissues in the plant. 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. If you cut into the plant, the vascular system (just under the bark) will be brown. Control Fusarium wilt by planting resistant varieties. Do not plant tomatoes in infected areas more than once every four years.

Plant tomato varieties that are disease resistant. This may be your only chance to control certain diseases. 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 and Betterbush but there are others.

Bacterial Wilt causes a rapid wilting and death of the plant.  The plant dies so quickly it does not have time to yellow.  Bacteria wilt browns the pith or middle of the stem. The pith may even be hollow. Cut a short section of the stem and suspend it in a clear glass of water. You may 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. Clean your shovel with a ten percent bleach solution after digging in this area and do not spread the infected soil. Do not plant these vegetables in this area for at least four years.

Southern blight is a white mold that rots the stem at or slightly above or below 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. You may not see the fungus on infected plants when the weather is dry. Bury all plant residues before planting, plant vegetables farther apart, and treat with Terraclor at planting if you have a problem with Southern blight. Some people 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.

Poor ripening shows up as white or grey areas in a ripening tomato. It can be caused by improper fertilization, virus diseases and high temperatures. Fertilize tomatoes monthly with a dry, granular fertilizer that is high in potassium. The fertilizer analysis tells what is in a fertilizer. 5-10-15 fertilizer has 5% nitrogen, 10% phosphate (phosphorus) and 15% potash (potassium). Use a fertilizer high in the last number (potassium) to help prevent uneven ripening. Prevent virus diseases by planting resistant varieties. Not all viruses can be prevented this way.

Blossom End Rot is the most depressing of the issues mentioned prior. Tomato plants will grow up looking beautiful and start to put on a fantastic fruit set, then the fruit will turn black and rot on the bottom end of the fruit opposite the stem. It is not caused by an insect or disease, but is a symptom of calcium deficiency in the fruit.  It can be caused by low calcium in the soil or other cultural factors, mainly fluctuating soil moisture (either too dry or too wet).  These conditions result in a deficiency in calcium available to the maturing fruit. While blossom end rot is bound to occur, it is treatable and cultural practices can be done to reduce its occurrence.  The calcium deficiency that causes blossom end rot is usually a result of climatic or cultural problems.  It is related to several factors, including calcium, nitrogen, and soil moisture levels.  It can occur even when there is abundant calcium in the soil and tissue tests show high levels of calcium in the plant.

  1. Applying lime or gypsum to the soil several months before planting can help prevent blossom end rot. This will put the needed calcium in the soil.  Foliar sprays of calcium won’t correct blossom end rot once it has occurred on the fruit.
  1. Avoid excessive use of nitrogen fertilizers. This can promote blossom end rot by causing excessive vegetative growth on the foliage, which can “rob” calcium that would otherwise go to the fruit.
  1. Remove any tomatoes that begin to show symptoms of blossom end rot. This may help the plant to produce subsequent healthy fruit.
  1. Keep the tomato plants watered regularly.  Tomato plants need about an inch of water per week to stay healthy.  Watering deeply once or twice a week is better than light, frequent watering. However, if your tomatoes are in pots or buckets, they may not be able to hold that much water and may need it more frequently.  Overwatering, though, can be just as bad.  Make sure that the plants aren’t water-logged.  Extreme fluctuations in soil moisture can cause an increase in blossom end rot.
  1. I have recommended some foliar calcium sprays such as “Blossom End Rot Stop” as some short term help. These treatments are only short term fixes and often work poorly on their own because of poor absorption and movement to the fruit area where it is needed.  You will need to look at other cultural practices to help solve this issue all the way!

I get asked so many times whether tomatoes grow well here, and I never can give a straight answer. There are so many variables that can cause issues, yet if the right cultural practices are put into play and the right variety decisions are made, they can have the best chance at growing well and producing yummy tomatoes! If you have any questions, suggestions, or want further information, please give me a call at or stop by the Effingham County Extension Office, (912)754-8040, 501 N. Richland Avenue, Rincon GA, 31326.

Joke of the Day: What’s the difference between knowledge and wisdom? Knowledge is knowing a tomato is a fruit; wisdom is not putting it in a fruit salad.