What Causes Tomatoes to Wither Up & Die?

Environmental Causes

• Just like any other plants, tomatoes will wither up and die if they are not cared for properly. Tomatoes need full sun, warm temperatures and moist but well-draining soil. Dry soil and very hot temperatures will quickly cause a tomato plant to wither and die. In addition, insects in the soil can also eat the root or stems of the plant, killing the plant. Nematodes are microscopic round worms that infect the roots of tomatoes and other plants. Cutworms and other insects can bore into or cut the stem, preventing water and nutrients from flowing up the plant. Spray your tomatoes with an insecticide if you suspect this to be the cause of the problem, and never plant tomatoes where nematodes have infected other plants.

Fungal Diseases

• Fungi can also be a health threat to tomato plants. Most types of fungi overwinter in the soil and have spores that spread on rain or splashing water. For that reason, it is important to water at the level of the soil, so that water does not sit on the leaves. Although some fungi do not affect the fruit and are simply unattractive, causing dark spots on the leaves, others are much more serious. Phytophthora infestans is one that can kill tomato plants. This fungal disease, often called "late blight," can kill a plant in as little as two weeks.

  Fusarium oxysporum, or Fusarium wilt, is another serious fungal disease that causes the plants to wilt and die. This fungus lives in the soil and is absorbed through the roots, where it spreads and kills the plant. Spraying your tomato plants with a fungicide and drenching the soil with fungicide can help prevent fungal diseases, as can planting disease-resistant varieties.

Bacterial Diseases

• Bacteria can also harm or even kill tomatoes. Xanthomonas vesicatoria spreads on water and attacks the plants when the tomatoes are green, causing rotten spots, deformed fruit and wilting. If the attack is severe, the plant will die. Ralstonia solanacearum, commonly called bacterial wilt, is a more serious disease that attacks the roots of the plant. The bacteria move into the stem and multiply, turning the insides of the flower to slime but leaving the leaves green. Tomatoes affected by this disease wilt quickly and die. No cure is available, and the bacteria can live in the soil for years.

Viruses

• Viruses can also cause tomatoes to wither up and die. Tobacco mosaic virus causes the leaves to wither and become deformed. Tomato spotted wilt virus causes the leaves to become spotted and the entire plant to wilt. In time, both viruses will cause the plant to die. Although there is no way to cure either of these diseases, which live in the soil, some varieties of tomatoes are resistant to the viruses.