Listed below are some of the most common tomato maladies and what you can do about them. Consult your local extension service for help diagnosing these and other problems. Also check out Insect and Disease Problems of Tomatoes,
an online guide from Texas A&M University.
first appears as a light-tan spot turning to a dark-brown sunken area at the bottom (blossom end) of the tomato. It affects both green and ripe tomatoes, and is most often caused by a fluctuating moisture supply that results in a lack of calcium in the plant.
Water regularly. Don't overfertilize with nitrogen. Plants supported by cages tend to be less susceptible to blossom-end rot than staked plants.
first appears as light, shiny blistered areas that eventually rot. It develops when tomatoes are suddenly or continually exposed to direct sunlight. The problem is most common on plants that lose a lot of foliage either by excessive pruning or from disease.
In very hot, sunny locations plant determinate varieties with dense foliage or grow indeterminate tomatoes in cages without pruning them. Prevent diseases as
described under "Blights and Leaf Spots".
Cracking around the stem
end and along the sides of ripening tomatoes often results from rapid fruit growth, often caused by a quick change in soil moisture,
especially when wet weather follows a dry spell. Too much nitrogen in the soil also contributes to the problem.
Select varieties that are less prone to cracking, such as 'Early Girl', 'Jet Star', 'Roma' and 'Sweet Million'. Keep the soil evenly moist with regular watering and mulch. Don't overfertilize.
Fusarium and verticillium wilts
are diseases caused by soil-borne fungi. The lower leaves on diseased plants turn yellow, wilt and die. Plants die prematurely.
Plant resistant varieties (indicated by the letters F and V after the variety name). Remove and destroy infected plants. Rotate plants annually. Or, grow plants in a commercial pasteurized potting mix in sterile containers.