Common Tomato Diseases: Causes, Symptoms, and Cures

Do you know what diseases to look for in your tomatoes? Keep your tomato crop in top shape by avoiding some common diseases:

early blight:

“Early blight affects the foliage, fruit, and stems of tomatoes. It is caused by the fungus Alternaria solani. Symptoms include dark spots that have concentric rings. A bull’s-eye pattern may develop. Older leaves develop first, and the leaves may discolor and turn yellow. If the leaves die, the tomatoes are exposed and may suffer from sunburn.

Cure: Affected tomato plants must be removed and all debris removed. This fungus is transmitted through the soil and will survive the winter. Therefore, anything that has touched an affected tomato plant should be removed, as it is most likely contaminated. You should use a hardy tomato cultivar and rotate your crops.

late blight:

Late blight is caused by the fungus Phytophthora infestans and affects both tomatoes and potatoes. It is especially dangerous if the weather is particularly cool and humid. Late blight was the fungus that caused the Irish potato famine. The leaves will have lesions and appear as irregular gray spots. If the weather is humid, white mold may appear around the spots. Once the tomato fruits become infected, they will develop dark regions that cover a large percentage of the tomato. The fungus can spread from one tomato plant to another by wind or rain.

Cure: Be sure to leave adequate spacing between tomato plants and avoid overhead watering, especially in the late afternoon or evening. Pull out and destroy affected tomato plants. Be sure not to use rotten potatoes in your compost, as it is a carrier of the fungus.

Bacterial wilt:

Bacterial wilt is caused by Ralstonia solanacearum, which enters the roots of tomato plants through wounds made by insects or natural wounds that occur where secondary roots begin to grow. The disease grows more easily in a warm, humid environment. Once inside the tomato plant, the bacteria multiply rapidly and fill the plant with slime. This leads to wilting of the plant, but the leaves remain green.

Cure: Bacterial wilt is very difficult to control as the bacteria can survive in the soil for several seasons. Be sure to remove infected tomato plants and the soil from affected tomatoes if possible. Crop rotation is known to help, especially with plants that are not affected by the bacteria, such as beans, cabbage, and corn.

southern blight:

Southern blight is caused by the fungus Sclerotium rolfsii. Usually the first symptom is tomato leaf drop, which is common with other wilts. Next, a brownish dry rot will develop on the tomato plant near the soil line. A white fungus will then begin to develop and lesions will develop on the stems. This in turn will cause the entire tomato plant to wither and die.
Cure: Unfortunately, the fungus can live for years in the soil, so if your crop develops, destroy the tomato plants and any soil they have touched. Also, rotating crops with plants that are not affected by the fungus could help, since you never know if all the contaminated soil was actually removed.”

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