Tomato Diseases: How To Identify And Treat It

Anthracnose is a prevalent fungal infection that leads to fruit decay. It is caused by the fungus Colletotrichum coccodes, it thrives in warm, wet conditions and poorly drained soil. The fungus typically spreads to the fruit from the soil through water splashes.

Identification

You will notice small, round, sunken spots on the fruit that are water-soaked and expand into larger areas with a darker, often blackened center and a concentric ring pattern.

Leaves may have small, round spots with yellow halos around them. The infection usually begins on immature fruit, but symptoms only appear as they ripen.

Treatment

Apply a tomato fungicide to the entire crop at the first signs of infection. Also, use copper-based fungicides before the disease appears. These fungicides help create a protective barrier on the plants.

A common tomato stem disease is botrytis gray mold. It is caused by the fungus Botrytis cinerea, which enters the plant through injuries, such as damaged stems or pruning cuts.

It can remain dormant for up to 12 weeks. Wind and water spread the spores, which are most active in cooler temperatures.

Identification

Look for a gray, fuzzy mold that appears on the surface of the fruit in the rotting areas. The rot appears as soft, water-soaked spots, which eventually collapse and turn mushy. You will also find sunken brown lesions on the leaves and stems. 

Treatment

Remove and dispose of infected fruits and leaves to reduce the fungus spread. Then, apply fungicides specifically designed for Botrytis, such as those containing chlorothalonil, boscalid, or pyraclostrobin.

Blight disease in tomato, like early blight, is caused by Alternaria fungus. This disease is more prevalent in hot, humid regions and remains in the soil for one year. Wet weather can bring on an attack

Identification

You will notice small, dark brown spots on older leaves with a concentric ring pattern. As the spots grow, the tissue around them turns yellow. This causes the leaves to gradually die off and fall prematurely. As the disease progresses, there will be dark, sunken lesions on the stems or branches of your plant.

Treatment

Prune affected leaves and stems and dispose of them properly to prevent fungus spread. Apply copper or sulfur sprays to prevent further development of the fungus.

To prevent the disease, space plants properly when planting and avoid overhead watering to reduce humidity and promote quicker drying. 

A tomato plant illness that affects the leaves but not the fruit is septoria leaf spot. Fungus spores, which can remain in the soil for up to two years, are carried by insects, tools, and water. It has similar symptoms to late blight, which can often lead to confusion.

Identification 

Septoria leaf spot disease on tomatoes is marked by small, dark spots on the leaves. These spots are round and have a gray or light tan center with a dark border.

As the disease progresses, the spots may grow larger and cause the leaves to yellow and die. 

Treatment

If your plant has this disease, treat it with repeated applications of copper-based fungicides or those containing chlorothalonil. Follow the product's instructions for application.

To prevent this disease, practice good garden sanitation by keeping your garden and garden tools clean. 

Fusarium Wilt or Verticillium Wilt is another sign of fungus on tomatoes. The former is caused by Fusarium oxysporum, while the latter is caused by Verticillium dahliae.

Identification

During warm weather, the entire plant wilts during the day but may revive at night. The symptoms start on the lower, older leaves and gradually move upward.

Eventually, the leaves on one side turn yellow, dry, become brown, and fall off. The inner tissue of the lower stem becomes red or black. Plants may die rapidly or within a week or more.

Treatment

Treatment is similar for both types of wilt. There is no fungicide for wilt. At most, all you can do is remove and dispose of infected plants and roots.

You should focus on prevention rather than cure by planting resistant varieties labeled VFN or FN and controlling the weed population. 

Many garden tomato problems reduce yields like bacterial specks. The bacteria Pseudomonas syringae causes this disease during persistent cool, wet weather. The bacteria by water splashing on the leaves during watering. 

Identification

Small, dark, water-soaked spots with a yellow halo appear on the leaves. These spots can range from pinpoint to about 1/8 inch in diameter.

Similar small, dark spots can develop on the fruit, often with a sunken center. The spots can be surrounded by a yellow or tan halo.  On rare occasions, the disease may cause dark, sunken lesions on the stems and petioles.

Treatment

Unfortunately, the disease cannot be cured. It can only be managed to stop it from spreading.

Use a copper fungicide during cool, wet weather to stop the pathogen from spreading. To prevent the disease, plant the tomatoes when the weather conditions are warmer and drier. 

A tomato plant illness you should watch out for is powdery mildew because it occurs easily. It spreads by different airborne fungi that exist according to temperature and humidity levels. Fruits are unaffected, but it does lead to crop loss.

Identification

The most noticeable symptom is a white or grayish powdery coating on the leaves, stems, and sometimes on the fruit. This coating can resemble flour.

Affected leaves may become distorted or curled. The edges might also turn brown or yellow.

Treatment

Remove infected leaves and buds and apply fungicides containing sulfur, potassium bicarbonate, or neem oil on the entire crop. For a chemical-free method, use one part milk to two parts water solution on affected areas.

This solution can help reduce fungal growth. Also, consider planting tomato varieties resistant to powdery mildew in the future to minimize the risk.

One of the many tomato growing diseases is damping off. This disease affects young tomato plants, leading to seedling death.

It is caused by several fungi, including Rhizoctonia, Pythium, and Fusarium, which thrive in damp, cool conditions and poorly drained soils.

Identification

The seedlings may suddenly wilt and collapse at the soil line, and the base of the stem might appear water-soaked and soft. Roots of affected seedlings may also turn brown and mushy.

Additionally, you might see a white, fuzzy mold on the soil surface or around the base of the plants.

Treatment

For this disease, prevention is everything. When planting tomatoes, start the seeds indoors, avoid using soil with excessive nitrogen, and maintain enough space between each tomato plant.

Once the seedlings have their first true leaves, add nitrogen fertilizer. Also, use well-draining soil, avoid overwatering, and sanitize your gardening tools.

Gray wall disease leads to blotchy ripening as it affects the fruit’s internal and external tissues, leading to blotchy ripening. It is not caused by fungus but is often related to environmental stress, poor nutrition, or inadequate light.

Identification

On the outside, the fruit may develop uneven ripening with grayish or brownish patches near the stem. The affected areas remain hard and do not ripen fully.

On the inside, the flesh may show dark, gray, or brown areas, and the tissue may appear hard and corky. 

Treatment/Prevention

There is no treatment, only preventive steps for gray wall.

You should provide ideal growing conditions for your plants by ensuring your plants receive consistent, balanced nutrition, improving air circulation by spacing plants appropriately and pruning to allow more light to reach the fruits. 

Like graywall, blossom end rot is not a disease caused by fungi or bacteria but rather a common physiological disorder in tomatoes. It occurs when the plant lacks calcium, caused by inconsistent watering or fluctuations in soil moisture.

Identification

Blossom end rot starts as a small, water-soaked spot at the bottom of the tomato. As the fruit develops, the spot enlarges, becoming dark, sunken, and leathery.

It often appears black or brown. The rest of the tomato may appear healthy, but the affected area will be inedible. Blossom end rot is more common when plants are rapidly growing.

Treatment

To treat this disease for tomato plants, you should stabilize the plant's calcium intake and maintain consistent soil moisture.

For that, water your plant regularly to prevent soil from drying out. Mulch the soil around your plants to retain moisture and regulate temperature.

Late blight is a fungal disease that affects tomatoes and is caused by the pathogen Phytophthora infestans. It thrives in cool, wet conditions and can rapidly destroy a tomato crop. This disease is a significant threat to tomato production.

Identification

Dark, water-soaked spots appear on leaves at the edges and then become bigger and brown or black. They are surrounded by a pale green or yellow halo.

A white, fuzzy mold may also develop on the undersides of the leaves. Additionally, dark lesions can form on stems, which may extend and cause the stem to collapse.

Treatment

You have to act quickly to treat late blight on tomatoes and prevent the disease from spreading.

Remove all infected plants and debris to reduce the source of the fungus. Apply a copper-based fungicide to healthy plants as soon as you notice symptoms. 

Buckeye rot is a tomato disease caused by the fungus Phytophthora nicotianae. It commonly affects tomatoes grown in warm, wet conditions and poorly-drained soils.

Identification

Look for sunken, dark brown to black lesions on the fruit's surface. These spots are small, water-soaked areas which can expand rapidly. The lesions may have a characteristic yellow halo around them.

As the disease progresses, the affected fruit may become soft and mushy. Buckeye rot typically starts on the lower fruit and can spread to other parts of the plant.

Treatment

To treat buckeye rot, start by improving soil drainage and avoiding overhead watering to reduce moisture around the plant. Apply fungicides specifically designed for Phytophthora diseases.

Remove and dispose of infected fruits to prevent the disease from spreading. Lastly, avoid planting tomatoes in the same spot year after year.

Leaf mold is a fungal disease caused by the fungus Cladosporium fulvum and usually appears in late summer or early fall. It thrives in humid, wet conditions and often develops in greenhouses or high-humidity environments.

Identification

You might find yellow to light green spots or patches, which may eventually turn brown on the upper leaf surface.

If you check the underside of these leaves, you will find a grayish or olive-green, fuzzy mold. The affected areas may also become dry and crispy, leading to leaf drop and reduced plant vigor.

Treatment

Apply fungicides containing active ingredients like chlorothalonil or copper.

Improve air circulation around your plants to reduce humidity and avoid overhead watering to keep the foliage dry. Regularly monitor your plants and treat them at the first signs of infection to keep the disease under control.

A viral disease for tomato plants is yellow leaf curl. It is caused by the Tomato Yellow Leaf Curl Virus (TYLCV), transmitted by whiteflies and thrives in warm climates.

Identification

To confirm the disease, look for these symptoms combined with whitefly infestations. The symptoms include distinctive upward curled and deformed leaves that are yellow at the edges and spread inward.

Severe cases may lead to premature leaf drop.  Affected plants may also exhibit stunted growth and reduced fruit production.

Treatment

Since the virus is transmitted by whiteflies, controlling these pests is crucial. Use insecticidal soaps, neem oil, or chemical insecticides to manage whitefly populations.

Also, consider using yellow sticky traps, row covers, or netting to protect plants from whiteflies. To prevent the virus from spreading, remove and destroy infected plants promptly. Do not compost them, as the virus can persist.

Root Knot Nematodes are tiny, worm-like pests that infest tomato plants, causing significant damage. These nematodes, mainly Meloidogyne species, live in the soil and attack the plant roots.

Identification

To identify this disease, look for swelling or knots on the roots. These galls can be small, round, or elongated, disrupting the root system.

Plants may exhibit stunted growth, with yellowing leaves and poor fruit development. Affected plants often produce fewer fruits or show signs of poor fruit quality.

Treatment

Consider using nematicidal treatments, like specific nematicide products, according to the manufacturer’s instructions for more severe infestations. If not, apply organic amendments, like compost or neem oil, to improve soil health and suppress the nematode population.

Also, soil solarization, which involves covering the soil with clear plastic to trap solar heat, can kill nematodes in the top layer of soil.

Bacterial wilt is caused by the bacterium Ralstonia solanacearum. It affects all crops in the Solanaceae family, like tomatoes, peppers, eggplant, and potatoes. It can be devastating if not managed promptly. 

Identification

The most noticeable symptom is the wilting of plants, often starting with the lower leaves and progressing upwards. Even if the soil is moist, the plants may still wilt because the bacteria disrupt the water transport system in the plant.

Leaves may turn yellow and curl out of nowhere. If you cut a stem and look inside, you will see a brown discoloration in the vascular tissue. If not treated, the affected plants eventually die.

Treatment

Maintain good soil hygiene and destroy infected plants to prevent the bacteria from spreading.

Avoid planting tomatoes or related crops in the same soil for several years. Improve soil drainage to reduce waterlogging to prevent bacterial growth.

Mosaic virus diseases for tomato plants are caused by various viruses, such as the Tobacco Mosaic Virus (TMV) or Cucumber Mosaic Virus (CMV). This disease disrupts the plant’s growth and can significantly reduce yield and quality.

Identification

The primary symptoms include mottled, mosaic-like patterns of light and dark green on the leaves, which can also become distorted and wrinkled.

Infected plants may show stunted growth and reduced fruit production. Leaves can also curl and turn yellow, and the overall vigor of the plant diminishes.

Treatment

There is no cure for the mosaic virus once plants are infected. The best approach is prevention. Use virus-resistant tomato varieties if possible, practice good garden hygiene by removing and destroying infected plants, and avoid using tobacco products in the garden.

Also, controlling insect vectors that can spread the virus, such as aphids, can help reduce the risk of infection.

Sunscald on tomatoes is a condition caused by excessive exposure to direct sunlight. Such excess sun exposure stresses the plant and affects the fruit on the side exposed to the sun.

Identification

Sunscald appears as white or light-colored, leathery patches on the fruit, often with a sunken texture. The affected areas may eventually become soft and start to rot. These patches are usually on the side of the fruit that faces the sun.

Prevention/Treatment

Use shade cloth or plant taller crops to shield tomatoes from intense sunlight. Ensure consistent watering to reduce plant stress and improve resilience.

Apply mulch around the base of the plants to help retain soil moisture and regulate temperature. Lastly, thin out excessive foliage for better air circulation and reduce heat buildup around the fruit.

Southern blight is caused by the fungus Sclerotium rolfsii. It thrives in warm, humid conditions and is particularly problematic in poorly-drained, sandy soils. The fungus can spread through contaminated soil, plant debris, or infected transplants.

Identification

Southern blight starts as small, water-soaked lesions at the soil line or lower stem. These lesions enlarge and turn brown or tan.

A characteristic white, cottony fungal mat may appear on the soil surface around the base of the plant, often accompanied by small, hard structures called sclerotia, which are the fungus's survival structures. As the disease progresses, the plant wilts and eventually dies.

Treatment

Ensure proper soil drainage to reduce humidity around the plant base and apply fungicides as a preventative measure. Clean up plant debris and infected material from the soil.

Tomato Pith Necrosis is a disorder in tomatoes caused by environmental stress, specifically related to high temperatures, irregular watering, or excessive soil moisture. This condition primarily affects the plant's vascular system, leading to internal tissue damage.

Identification

The disease is characterized by internal browning and decay of the pith tissue in the tomato stems. Externally, you might see stunted growth and poor fruit development. The stem may appear discolored or show signs of wilting.

Treatment

To manage Tomato Pith Necrosis, focus on maintaining consistent soil moisture and avoiding extreme temperature fluctuations. Ensure proper watering practices, providing adequate irrigation without waterlogging.

Using mulch can help regulate soil moisture and temperature. Additionally, choose heat-resistant tomato varieties to reduce the risk of developing this condition