Gardening Plant Problems Plant Diseases

Save Your Tomato Plants From These 15 Common Diseases

Keep Your Plants Healthy for a Bountiful Harvest

Red tomatoes hanging on diseased vine closeup

The Spruce / Heidi Kolsky

Growing fresh tomatoes is one of the true joys of vegetable gardening. However, tomato plant diseases happen and the causes are often related to uncontrollable weather conditions. If you know your area is prone to a certain disease, you should look for varieties that are listed as resistant (ask your local cooperative extension service for recommendations).

Tomato diseases can be fatal unless you manage them in a timely manner. While there are a variety of diseases, they mostly come in fungal and bacterial form. Some of the most common are crown and root rot, fusarium wilt, early blight, rhizoctonia, and more.

It is important to catch any disease early before it spreads to all of your tomato plants and possibly other plants in the same family (such as potatoes, eggplants, and peppers). Some diseases affect the foliage, while others attack the fruit. Learn how to treat these common tomato plant diseases to keep your plants healthy. 

Tomato Plant Disease Control and Prevention

Control and prevent tomato plant disease by growing the plants on support structures so the foliage does not touch the ground. Growing the plant in full sun (six hours a day), as well as proper spacing between plants for air circulation, prevents soggy conditions.

Rotating tomatoes to different areas of your garden is called crop rotation. Crop rotation is done for a variety of reasons, including to avoid diseases still lurking in the soil from the last crop as well as to prevent pests and diseases from making their home in the soil.

Early Blight

Early blight is a fungal disease that can affect the foliage, stems, and fruit of tomatoes.

Symptoms: Dark spots with concentric rings develop on older leaves first that touch infected soil. The surrounding leaf area may turn yellow. Affected leaves may die prematurely, exposing the fruits to sunscald. It also infects stems and fruit, presenting as black leathery spots on fruit.

Management: Early blight fungus overwinters in plant residue and is soil-borne. It can also come in on transplants and survives in seeds of infected plants. Remove affected plants and thoroughly clean fall garden debris. Do not compost affected plants. Wet weather and stressed plants increase the likelihood of an attack. Copper and/or sulfur sprays can prevent further development of the fungus. The biofungicide Serenade helps to minimize problems with early blight. In areas impacted by early blight, look for cultivars that are resistant to the disease with a tag that says that it's "Resistant to EB (Early Blight)."

Tomato plant vine with early blight on green leaf tips

The Spruce / Heidi Kolsky

Stemphylium Gray Leaf Spot

Gray leaf spot is a fungal disease that affects mainly the leaves of tomatoes, starting with the oldest leaves, although it can also infect the stems on the plant. It does not infect the fruit, although the disease can be harbored in the seeds of the infected plant.

Symptoms: Small, dark spots that can be seen on both the top and bottom surfaces of the leaves. The brown spots are surrounded by a yellow halo. The spots enlarge and turn a grayish brown. Eventually, the centers of the spots crack and fall out. Surrounding leaf areas will turn yellow and the leaves dry out and drop. Fruit production is inhibited.

Management: Warm, moist conditions worsen gray leaf spot problems. Remove all affected plants and fall garden debris. Do not compost infected plants. Cherry and grape tomato plants are most often impacted. Select resistant varieties. Rotate crops to avoid planting in infected soil.

Late Blight

Late blight is a mold disease that affects the leaves, stems, and fruit of tomatoes. A strain of late blight is the disease responsible for the Irish Potato Famine. Late blight spreads rapidly. Cool, wet weather encourages the development of the disease. Late blight is caused by the oomycete Phytophthora infestans, which is not a true fungus but still causes devastation to plants. If you suspect you have late blight, contact your local extension service for positive identification. There are actually many strains of late blight.

Symptoms: Greasy-looking, irregularly shaped dark brown blotches with green-gray edges on leaves. A ring of white mold can develop around the spots, especially in wet weather. The spots eventually turn dry and papery. Blackened areas may appear on the stems. The fruit also develops large, irregularly shaped, greasy gray spots and can turn mushy from a secondary bacterial infection.

Management: Late blight can decimate a tomato crop. Copper sprays offer some control. Serenade works best as a deterrent, rather than a cure. Late blight can overwinter in soil. Since strains can spread to potatoes, it also overwinters in potato debris and seed, even in colder areas. Remove all debris and don't save seed potatoes. Rotate crops to prevent infections the following year.

Blight in Tomato
FerhatMatt / Getty Images

Septoria Leaf Spot

Septoria leaf spot is a fungal infection that affects leaves but not the fruit. It is sometimes mistaken for late blight.

Symptoms: The infection appears as small, dark spots that enlarge to 1/4-inch diameter. The spot develops a tan or gray center, and the leaves eventually wilt and fall off. Older leaves are affected first.

Management: Copper sprays and Serenade fungicide are somewhat effective at halting the spread of symptoms. Remove infected leaves to prevent the spread of spores to other leaves, as water splashing on the leaves helps transmit the disease.

Southern Blight

Southern blight is a fungal disease that manifests as a white mold growing on the stem near the soil line. It not only affects tomatoes, but it also impacts peppers, beans, cantaloupes, carrots, potatoes, watermelon, and peanuts, among others.

Symptoms: Dark, round spots appear on the lower stem near the soil line, and both the outer and inner stem becomes discolored. Southern blight fungus, Athelia rolfsii, girdles the tomato stem and prevents the plant from taking up water and nutrients. Young plants may collapse at the soil line. Fruit near the stem can become infected as well.

Management: Use a fungicide as a preventative. The fungus remains in the soil for several years. Dispose of infected plants and plant debris but do not compost. Rotate crops.

Rotten Moldy Tomato
DIMUSE / Getty Images

Fusarium or Verticillium Wilt

Fusarium wilt or verticillium wilt are often confused with one another, but they are both fungal diseases with similar issues. The names can be misleading, as sometimes the leaves will turn yellow, dry up, and may never appear to wilt. Fusarium wilt thrives in warmer, dry conditions while verticillium occurs more often in cooler weather.

  • Fusarium wilt is caused by Fusarium oxysporum.
  • Verticillium wilt is caused by Verticillium dahliae.

Symptoms: Their symptoms are very similar. Yellow blotches on lower leaves that eventually turn into brown dead spots. Symptoms start on older, lower leaves and move upward. The diseases wilt and stunt the plants, producing smaller fruits that may suffer from sunscald. There will be brown streaks inside of the stems.

Management: Management is similar for both types of wilt. The fungi can persist in the soil for many years, so crop rotation and selection of resistant varieties are crucial. Always remove affected plants and their roots.

Tomato plant with leaves with verticillium wilt over hanging tomatoes

The Spruce / Heidi Kolsky

Anthracnose

Anthracnose is a very common fungus that causes tomato fruit to rot.

Symptoms: Small, round, sunken spots appear on the fruit. The spots increase in size and darken in the center. Several spots may merge as they enlarge. The fungus is often splashed onto the fruit from the soil. It can also take hold on spots of early blight or dying leaves. Wet weather and poorly drained soils encourage the development of anthracnose. Overripe tomatoes that come in contact with wet soil are especially susceptible.

Management: Copper sprays offer some resistance. Remove the lower 12 inches of leaves to prevent contact with the soil. Water only the base of the plant, not the leaves. Spores overwinter in soil, so practice crop rotation.

Bacterial Speck

Bacterial speck is one of several bacterial problems that affect tomatoes. Caused by the bacteria Pseudomonas syringae pv. tomato, it reduces yields. There's no cure for the plants once infected. It's most prevalent in cool, moist weather.

Symptoms: Tiny, dark spots, usually with a yellow border, on fruit and leaves. The spots may be raised, flat, or sunken.

Management: Avoid splashing water on leaves. The disease can be transmitted to healthy plants by water, hands, and garden tools. Remove affected plants and debris--do not compost. Practice crop rotation.

Orange-red tomatoes hanging on vine with bacterial speck

The Spruce / Heidi Kolsky

Blossom End Rot

Blossom end rot is generally attributed to a lack of calcium availability during fruit set. This could be caused by too much high-nitrogen fertilizer or uneven watering, resulting in fluctuations in nutrient availability. It's a physiological disorder, not a disease, but it still results in loss of fruit.

Symptoms: Dark brown/black spots develop at the blossom end of the fruit and enlarge as the fruit rots. The spots look water-soaked.

Management: Remove affected fruit and provide regular, deep waterings. Add garden lime to soil to help with the uptake of water and nutrients. Use a fertilizer low in nitrogen and high in phosphorous.

Green tomato hanging on vine with blossom end rot on bottom closeup

The Spruce / Heidi Kolsky

Buckeye Rot

Buckeye rot is more common in Southern states, especially during warm, wet periods.

Symptoms: Buckeye rot affects both green and ripe fruit. The small brown spot will enlarge and develop concentric rings that resemble a buckeye. The affected area may appear round or oblong, and the firm lesion with smooth margins becomes soft and decayed as the disease progresses.

Management: Remove affected fruit and keep future fruits from contact with the soil. Avoid surface water.

Gray Wall 

Gray wall is essentially a ripening problem. There's no known associated pathogen.

Symptoms: The green fruits may have a gray cast or flattened, gray blotches. Ripe fruit has a mottled appearance and green or brown areas on the inside of the fruit.

Management: Good growing conditions help prevent gray wall. Make sure plants are not heavily shaded and are receiving even waterings and fertilizer and that the soil is not compacted around the roots. Cool temperatures and stressed or unhealthy plants also contribute to the problem.

Leaf Mold

Leaf mold is a fungus caused by Passalora fulva and it occurs most frequently in humid conditions. 

Symptoms: Leaf mold appears as pale green or yellowish spots on the upper leaves. When it's very humid, the spots occur on the bottom surfaces of the leaves and then become covered in a gray, velvety growth of fungal spores. Fruits can have a leathery, blackish rot near the stem.

Management: Increasing air circulation by pruning, spacing, and staking tomato plants can control the disease. to increase air circulation helps to control the disease. Avoid watering overhead to keep leaves dry. Crop rotation is important. A preventative fungicide can be used.

Tomato Pith Necrosis

Tomato pith necrosis is a disease caused by soil-borne Psudomonas bacteria. It occurs during cloudy, cool, and moist conditions.

Symptoms: An early symptom is the blackening of the stems and leaves. Later symptoms involve split stems or stems that shrink and crack. The pith (stem interior) disintegrates and becomes hollow, disrupting water flow, and yellowing leaves.

Management: Warmer weather can resolve the issue. But to manage the disease, do not water from above, keep soil adequately moist, and remove and dispose of dead and diseased plants and roots. Since the bacteria can remain in the soil for a few years, it's best to rotate crops.

Damping Off

Damping off is a fungal disease caused by Rhizoctonia that affects tomato plant seedlings. This fungus develops in cool, wet, and rich soils.

Symptoms: Seedlings may fail to emerge or the stems are water soaked.

Management: When starting tomato plant seeds, start them indoors and do not put seeds in soil with high nitrogen levels. You should add nitrogen fertilizer after seedlings are more established, which is when they have their first true leaves. As always, it's a good practice to keep the surface of the soil dry between waterings.

Mosaic Virus

Mosaic virus is transmitted in a variety of ways, through seed, grafting, pests, or handling by human hands. The virus is a concern throughout the growing season. It's also a difficult virus to eradicate since it survives in plant debris for over 100 years.

Symptoms: In addition to curling, the leaves become mottled, new leaflets are small, and infected fruit is brown inside. Growth can be generally light in color. The fruit may have a mottled mosaic look (alternating colors) on the skin.

Management: Control of mosaic virus is difficult. Reflective mulches may help prevent the problem.

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  1. Early Blight of Tomato. University of Minnesota Extension.

  2. Common Diseases of Tomatoes. Mississippi State University Extension.

  3. Late Blight of Tomato and Potato. University of Maryland Extension.

  4. Southern Blight of Tomato and Pepper. North Carolina State Extension.

  5. Anthracnose - Vegetables. University of Maryland Extension.

  6. Vegetable: Tomato, Buckeye Rot. University of Massachusette Center for Agriculture.

  7. Tomato Diseases and Disorders. Clemson University Cooperative Extension Service.

  8. Tomato Diseases and Disorders. Clemson University Cooperative Extension Service.

  9. Mosaic Diseases Caused by Potyviruses. University of California.