Alabama falls between USDA temperate zones 7 and 8. Tomatoes in these regions can be started indoors early and then planted in the ground after the last average frost date of the year. If harvested regularly, tomatoes grown in Alabama will continue to produce fruit until the first frost of the year. However, tomatoes may suffer from a number of diseases, insects or other problems. There are some easy steps that you can take to identify the problems and treat the plants accordingly.
Determine the history of the land that you have planted your tomatoes on. If you are planting on land that has held tomatoes, potatoes, eggplant, strawberries, blackberries, raspberries or other related crops, your tomatoes may suffer from blight left behind by a crop from previous years. Tomatoes affected by blight will appear to have wilted, yellowed leaves, sunken stems and white fungus growing on the stem near the base of the plant.
Observe what plants are placed near tomatoes. Tomatoes planted near certain plants such as walnut trees or Kohlrabi (turnip plant) will be affected by the presence of these plants. Kohlrabi stunts the growth of tomatoes, and tomatoes planted near walnut trees will suffer from walnut wilt caused by the toxins produced by the tree. Walnut wilt causes tomatoes to turn brown and die. Tomatoes planted near corn will be affected by worms that eat the corn.
Look over tomato fruit for signs of distress. Often problems with tomato plants show up in fruit. If the fruit appears to be rotten in light or dark concentric bands wherever it touches the ground, the plants suffer from buckeye rot. Blossom end rot resembles dark, sunken areas on the blossom end of tomato fruit. It is caused by frequent rain or an imbalance in pH denies the tomato plants calcium. Blotchy or gray fruit with a brown interior is a sign of adverse growing conditions such as compacted soil, high nitrogen, low potassium or low-light intensity. If the surface skin has split or the tomato has become lumpy, this condition is known as catfacing. Catfacing is caused by poor environmental conditions such as extreme cool or warm weather when the fruit develops. Greasy, water-soaked spots near the stem end of the tomato is a sign of late blight.
Examine the plants for further signs of distress. The symptoms of disease and insect infestation leave obvious signs on plants that may include stunted growth, spots on leaves, rot and deformities. Dig away the soil at the roots of stunted or wilted tomatoes to determine if the roots have developed knots or galls. This is a sign of root-knot nematodes. If the roots of the plants are fine, but the leaves develop ring spots, then your plants have become infested with thrips. Look on the underside of leaves and stems of plants that exhibit blotchy fruit and thin leaves. If you see tiny colonies of bugs, your tomatoes have an infestation of aphids. Bacterial canker will stain the vascular system of plants reddish brown and cause spots on fruit.
Uproot your plant or take cuttings, photos and fruit samples. Place organic samples in plastic freezer bags and take the evidence to your local county extension service. The Alabama Cooperative Extension Service maintains agencies in each county. Agents at each extension office can positively identify the issues with your tomato plant and recommend solutions.