Common Tomato Diseases

One of the most recognizable and treatable tomato diseases is Blossom End Rot. This common tomato disease usually occurs on the first fruits of the season or on tomatoes that ripen after a drought.

Identification:

Blossom End Rot can occur in ripe and green tomatoes. The fruits have dark blemishes or a black patch on the bottom, or blossom-end, of the fruit.

Blossom drop happens when the yellow flowers on the tomato plants dry up and don't form fruits. It's usually caused by weather-related factors.

Identification:

Blossom drop is fairly easy to identify. If a tomato blossom is pollinated, then the fruit begins to form. If it's not, then the yellow flowers dry up and fall off the plants. Blossom drop is usually caused by too cold or too hot weather, such as:

• Nighttime temperatures below 55 degrees F.
• Several days of 90-plus degree days and nighttime temperatures above 72 degrees F.
• Humidity levels above 70 percent or below 40 percent
• Strong winds

It can also be caused by too little or too much nitrogen or insect damage.

Although not technically a tomato disease, fruit cracks are a common problem for gardeners. While the tomatoes are still edible, they are unattractive and can also invite pests and birds to attack the fruits. Usually, cracking fruits happens when hot, rainy weather follows a dry spell. The plants take in water too rapidly, causing the fruits to swell and develop cracks.

Identification:

Fruit cracks occur in two patterns. The cracks are concentric circles starting at the top of the fruit or the fruit has vertical cracks.

Early blight is one of many fungal diseases that can damage your tomato plants. This common fungal disease affects tomatoes as well as other nightshade plants, including potatoes and eggplants. The fungus affects the leaves, but can also damage the stems and fruits—and reduce yields.

Identification:

The first symptoms of an early blight infection are usually small, dark spots on the leaves at the bottom of the tomato plant. Rings start to form around the leaf spots and the tissue around the spots starts to yellow. Eventually the leaves turn brown and fall off the plant. This can leave the plants with very few leaves. The stems and fruits may also be affected.

Late blight is one of the most devastating fungal diseases that infects tomatoes (and potatoes). The infection can quickly spread from the leaves to the fruits and destroy the plants, and this fungus seems to really take off during cool, wet weather. Late blight was the cause of the Irish potato famine in the 1840's.

Identification:

Late blight symptoms start as large, dark brown spots, edged in gray-green, on the leaves. The fungus spreads through the plant and to the fruits, leaving brown, mushy spots. The lesions on fruits affected by late blight tend to be lighter colored, brown or tan, than lesions on fruits affected by early blight. Late blight can infect all tomato plants within a matter of days. Infected plants often look like they've been damaged by frost.

Another destructive fungal disease, septoria, also called septoria leaf spot, is common in wet, humid areas. The fungus damages the foliage on tomato plants and can drastically reduce yields.

Identification:

Septoria leaf spot first appears as small lesions or spots on the lower leaves and stems of the tomato plant. While septoria lesions are usually smaller than early blight lesions, septoria can quickly blight leaves and move to other areas of the plant. Once it spreads to the rest of the plant, it will weaken the plant and cause serious damage.

Damping off is a disease that affects germinating seeds and seedlings, especially in indoor seed-starting situations. However, it can also happen if direct sowing tomatoes into cold, wet garden soil. Caused by fungus or mold, damping off causes the seedlings to rot.

Identification:

If the seedlings fail to emerge from the soil, it may be caused by damping off. Other signs of damping off are soft, mushy and discolored seedling stems and wilting, gray-brown seedling leaves. The young seedling may also have white-cobweb looking growth around it.

Another common fungal disease is anthracnose. Unlike many other fungal diseases, anthracnose damages the fruits, not the plants. Black spots start to develop on ripe and just-harvested fruits. The spots grow quickly, causing the fruit to rot.

Identification:

Anthracnose on tomatoes starts as small, dark spots that are slightly depressed. The spots grow in size and often have a pattern of concentric circles around them. The disease can affect tomatoes ripening on the vine as well as harvested tomatoes. Usually gardeners see it when plants are really producing, and they have an excess of tomatoes sitting on the counter or picnic table.

Fusarium wilt is a fungal disease that affects tomato, eggplant and pepper plants. As its name implies, the disease causes the plants to yellow and wilt.

Identification:

Fusarium wilt causes the tomato leaves to turn yellow. In the early stages, one section of the plant may be affected and the leaves will wilt during the heat of the day. As the disease progresses, more of the plant is affected and the leaves turn brown. Eventually, the plant will die. Fusarium wilt is sometimes confused with the less common verticillium wilt. Plants affected with verticillium wilt usually have more uniform yellowing of the leaves on the lower portion of the plant. A diagnostic plant sample can confirm the disease.

Verticillium wilt is a fungal disease that affects tomato plants as well as pepper, eggplant and potato plants. Common symptoms are the yellowing and wilting of lower leaves of the plants. As the disease progresses, the leaves brown and the plant often dies.

Identification:

Verticillium wilt usually starts in the leaves closest to the ground, and can easily be confused with fusarium wilt. Usually verticillium wilt is more prevalent when temperatures are cool. Plants affected with verticillium wilt usually yellow more slowly and the disease progression is slower. However, as the disease progresses, the leaves will brown. A plant tissue test can diagnose what wilt is affecting your tomato plant.