Identify and Treat 10+ Common Tomato Diseases

Tomato Wilting Leaves

Tomato wilting leaves can be a sign of various issues, including insufficient water, overwatering, or disease. Wilting due to underwatering is often temporary and can be resolved by providing adequate water. Overwatering, on the other hand, can lead to root rot, causing leaves to wilt and turn yellow. 

Diseases such as Fusarium wilt and Verticillium wilt are common causes of wilting in tomatoes. Fusarium wilt typically affects one side of the plant first, causing lower leaves to yellow and wilt, while verticillium wilt causes a more uniform yellowing and wilting of leaves. Both diseases are soil-borne and can be managed by using resistant varieties, rotating crops, and maintaining good soil health. Additionally, pests like nematodes can damage roots, leading to wilting.

Tomato Diseases Images - Tomato Wilting Leaves

How to Identify Tomato Wilting Leaves？

• Check Soil Moisture: Determine if the soil is too dry or too wet. Wilting can be a sign of underwatering, especially if the soil is dry and cracked. Overwatering can lead to root rot, causing leaves to wilt and turn yellow.
• Inspect for Diseases: Look for signs of fusarium wilt, which often starts with yellowing and wilting on one side of the plant, affecting lower leaves first. Verticillium wilt causes a more uniform yellowing and wilting of leaves, starting from the bottom and moving upwards. Both diseases can be identified by cutting open the stem and looking for discolored vascular tissue.
• Examine for Pests: Check for pests like nematodes, which can damage roots and cause wilting. Look for galls or knots on the roots. Aphids and other sucking insects can also cause wilting by feeding on plant sap.
• Consider Environmental Factors: Extreme temperatures, either too hot or too cold, can cause temporary wilting. Ensure your plants are not exposed to direct sunlight during the hottest parts of the day and are protected from frost.
• Monitor for Nutrient Deficiencies: Nutrient deficiencies, especially potassium, can cause wilting. Look for other symptoms like yellowing leaves or poor growth.

How to Treat Tomato Wilting Leaves？

1. Determine the underlying cause. If underwatering is the issue, provide consistent and adequate water, ensuring the soil is moist but not waterlogged.
2. For overwatering, reduce watering frequency and improve soil drainage to prevent root rot.
3. If a disease like Fusarium or verticillium wilt is suspected, remove and destroy infected plants to prevent spread, and consider using resistant tomato varieties in future plantings.
4. For pest-related wilting, such as nematodes, rotate crops and use nematode-resistant varieties.

Yellow Leaf Curl Virus

The Tomato Yellow Leaf Curl Virus (TYLCV) is a significant threat to tomato crops.  It belongs to the genus Begomovirus within the family Geminiviridae.  It is primarily transmitted by whiteflies, specifically the species Bemisia tabaci.  Infected tomato plants exhibit characteristic symptoms, including upward curling of leaves, yellowing of leaf margins, stunted growth, and reduced fruit yield.  The virus can cause severe economic losses in tomato production areas worldwide.

Tomato Diseases Images - Yellow Leaf Curl Virus

How to Identify Tomato Yellow Leaf Curl Virus？

• Leaf Yellowing and Curling: Young leaves may show interveinal and marginal yellowing, and leaves curl upwards or downwards.
• Leaf Crumpling and Size Reduction: Infected leaves often appear crumpled and smaller than normal.
• Stunted Growth and Flower/ Fruit Drop: Plants may be significantly shorter than healthy ones and may experience flower and fruit drop.
• Bushy Appearance: Infected plants may have a bushy appearance due to apical proliferation.

How to Treat Tomato Yellow Leaf Curl Virus？

1. Remove and destroy symptomatic plants to prevent the spread of the virus.  Bag infected plants and allow them to desiccate for 1-2 days before disposal.  Avoid composting infected plants.
2. Use insecticides such as azadirachtin (Neem), pyrethrin, or insecticidal soap to manage whitefly populations. Rotate between different insecticides to prevent resistance. Insect-proof screens and sticky yellow traps can also be effective.
3. Plant TYLCV-resistant or tolerant tomato varieties to reduce the impact of the virus on crop yield.
4. Use reflective mulches, such as silver or aluminum-colored mulches, to repel whiteflies and reduce virus transmission.
5. Implement crop rotation, proper plant spacing, and weed management to reduce the spread of whiteflies and the virus. Avoid planting new fields near older fields with infected plants.
6. Introduce natural predators of whiteflies, such as parasitic wasps (Encarsia formosa, Eretmocerus eremicus), predatory beetles (Delphastus catalinae), and predatory mites (Amblyseius swirskii).

Fusarium Wilt

Fusarium wilt is a serious soil-borne fungal disease that affects tomatoes, caused by the fungus Fusarium oxysporum f. sp. Lycopersici. This disease typically manifests as yellowing and wilting of leaves, starting with the lower leaves and progressing upwards.  Often, only one side of the plant is initially affected. 

As the disease progresses, the leaves turn brown and die, and the plant may exhibit stunted growth. The fungus invades the plant's vascular system, blocking water and nutrient transport.

Tomato Diseases Images - Fusarium Wilt

How to Identify Tomato Fusarium Wilt？

• One-Sided Yellowing: Initial symptoms include yellowing of the lower leaves, often restricted to one side of the plant or one branch. This one-sided yellowing is a distinctive feature of Fusarium wilt.
• Wilting: Leaves will wilt, especially during the warmest part of the day, and may recover slightly at night in the early stages. As the disease progresses, the wilting becomes permanent.
• Browning of Vascular Tissue: If you cut open the stem near the base, you will see dark brown streaks in the vascular tissue, indicating that the fungus has blocked the plant's water-conducting pathways.
• Progressive Leaf Death: The yellowing and wilting will progress upwards from the lower leaves, eventually affecting the entire plant.
• Stunted Growth: Infected plants often exhibit stunted growth and produce fewer fruits.
• Healthy Roots Initially: In the early stages, the roots may appear healthy, but they will eventually rot as the disease progresses.

How to Treat Tomato Fusarium Wilt？

To treat tomato Fusarium wilt, focus on prevention and management, as there is no effective cure once plants are infected. Use resistant tomato varieties, practice crop rotation for at least three years, and maintain healthy soil. Infected plants should be removed and destroyed to prevent the spread of the fungus.

Verticillium Wilt

Tomato verticillium wilt is a soil-borne fungal disease caused by the fungus Verticillium dahliae. It affects a wide range of plants, including tomatoes, and is characterized by yellowing and wilting of leaves, starting from the bottom and moving upwards. 

Unlike Fusarium wilt, Verticillium wilt often affects the entire plant rather than just one side. Infected plants may show stunted growth and reduced yields. The fungus invades the plant's vascular system, blocking water and nutrient transport.

Tomato Diseases Images - Verticillium Wilt

How to Identify Tomato Verticillium Wilt？

• Yellowing of Leaves: Initial symptoms include yellowing of the lower, older leaves, often in a V-shaped pattern that narrows from the leaf margin. Unlike fusarium wilt, the yellowing is usually uniform across the entire plant rather than restricted to one side.
• Wilting: Leaves will wilt, especially during the hottest part of the day, and may recover slightly at night in the early stages. As the disease progresses, the wilting becomes permanent.
• Leaf Drop: Infected leaves will eventually turn brown and drop off, leading to defoliation.
• Stunted Growth: The overall growth of the plant may be stunted, and fruit development will be poor.
• Vascular Discoloration: Cut open the stem near the base of the plant to look for light brown to cream-colored streaks in the vascular tissue. This discoloration is a key diagnostic feature of verticillium wilt.
• Cool Weather: The disease is favored by cool soil and air temperatures, typically between 68° to 75° F.

How to Treat Tomato Verticillium Wilt？

1. The best approach is to use resistant tomato varieties. You can plant tomato varieties that are resistant to verticillium wilt. These varieties are often labeled with a "V" on the plant tags or seed packets. Examples include 'Jet Star', 'Celebrity', 'Cherry Grande', and 'Roma'.
2. Rotate crops to avoid planting tomatoes or related plants (such as peppers and potatoes) in the same soil for at least three to four years. This helps reduce the fungal population in the soil.
3. Improve soil health by adding organic matter, which can enhance drainage and reduce the risk of infection. Avoid planting in poorly drained areas.
4. Remove and destroy infected plant material at the end of the season. Do not compost diseased plants. Clean stakes, cages, and other gardening tools to prevent the spread of the fungus.

Anthracnose

Tomato anthracnose is a fungal disease caused by a species of the fungus Colletotrichum, most commonly Colletotrichum coccodes. Primarily, it affects ripe and overripe tomatoes, causing small, sunken, water-soaked spots that enlarge and develop dark, concentric rings.  These spots can become soft and mushy, leading to fruit rot. On leaves, anthracnose can cause small, circular spots with dark centers.  

The disease thrives in warm, wet conditions and spreads through splashing water and infected plant debris.  To manage anthracnose, it is important to harvest fruits promptly, avoid overhead watering, and remove and destroy infected plant material. 

Tomato Diseases Images - Anthracnose

How to Identify Tomato Anthracnose？

On Fruits

• Circular, Sunken Lesions: Initially, small, circular, and sunken spots appear on ripe or overripe fruits. These spots are water-soaked and can enlarge over time.
• Concentric Rings: As the disease progresses, the lesions may develop concentric rings and become darker.
• Salmon-Colored Spores: Under humid conditions, the center of the lesions may produce salmon-colored spores.

On Leaves

• Small, Dark Spots: On older leaves, small, dark spots with yellow halos may appear.
• Leaf Yellowing and Defoliation: Infected leaves may turn yellow and drop off prematurely.

How to Treat Tomato Anthracnose？

1. Rotate crops to avoid planting tomatoes or other solanaceous crops in the same spot more than once every 3 - 4 years.
2. At the end of the season, remove and discard infected plant debris to prevent the fungus from overwintering.
3. Mulch under plants to reduce soil splash and keep fruit from contacting the soil. Stake or cage plants to improve air circulation and keep fruit off the ground.

Tomato Pith Necrosis

Tomato pith necrosis is a bacterial disease caused by Pseudomonas corrugata and other Pseudomonas species, as well as Pectobacterium carotovorum.  It affects the pith, or central portion, of tomato stems, turning the tissue from fleshy to mushy and discolored.  

Symptoms first appear when the first fruit set is close to the mature green stage.  Infected plants show yellowing and wilting of leaves, dark brown to black lesions on the stem, and profuse adventitious root formation along the stem.  When the stem is cut open, the pith may appear hollow, discolored, or chambered.  This disease thrives in high humidity, cool night temperatures, and high nitrogen conditions, which promote rapid plant growth.

Tomato Diseases Images - Tomato Pith Necrosis

How to Identify Tomato Pith Necrosis?

• Leaf Yellowing and Wilting: Initial symptoms often include yellowing (chlorosis) of young leaves and wilting of the upper portions of the plant. The lower leaves may also wilt.
• Stem Lesions: Dark brown to black lesions may form on the stem. These lesions can extend along the stem and may split the stem open.
• Adventitious Roots: Many adventitious roots (aerial roots) may form along the stem. These roots can be a sign of the disease, especially in conditions with high humidity.
• Hollow or Discolored Pith: When the stem is cut lengthwise, the pith (the central part of the stem) may appear hollow, discolored, or chambered. The discoloration is usually darkest at the base of the plant, but does not extend into the roots.
• Fruit Symptoms: In some cases, fruit may develop small, round black spots that eventually become surrounded by soft rot.
• Random Distribution: Affected plants are often scattered randomly in the field or greenhouse.

How to Treat Tomato Pith Necrosis?

1. Reduce high humidity and improve air circulation to prevent the spread of the disease. Avoid excessive nitrogen fertilization, especially early in the season, to reduce rapid growth that can make plants more susceptible. Apply systemic fungicides like thiophanate-methyl or chlorothalonil during the early stages of infection. If the disease is severe, remove and destroy infected plants to prevent further spread. Additionally, ensure that tomato stakes and other equipment are disinfected before reuse to avoid spreading the bacteria.

Mosaic Virus

Tomato Mosaic Virus (ToMV) is a plant pathogenic virus that belongs to the genus Tobamovirus.  It infects a wide range of plants, including tomatoes, peppers, cucurbits, and other crops.  The virus is highly persistent and can survive in seeds, soil, and plant debris for extended periods.  

Symptoms vary depending on the host plant but often include mottling and mosaic patterns on leaves, stunted growth, and reduced yield.  ToMV is transmitted mechanically through contact with infected plant material, tools, or hands, making it challenging to control in agricultural settings.

Tomato Diseases Images - Mosaic Virus

How to Identify Tomato Mosaic Virus?

• Leaf Symptoms: Initial symptoms often include yellowing (chlorosis) of young leaves and wilting of the upper portions of the plant. Lower leaves may also wilt.
• Stem Symptoms: Dark brown to black lesions or streaks may appear on the surface of the peduncles, leaf petioles, and stems. When the stem is cut lengthwise, the pith may appear discolored, hollow, or chambered. The discoloration is usually darkest at the base of the plant but does not extend into the roots.
• Adventitious Roots: Many adventitious roots may form along the stem.
• Fruit Symptoms: Fruit may develop small, round, black spots that eventually become surrounded by soft rot. However, fruit symptoms are rare.
• Plant Distribution: Affected plants are usually scattered randomly throughout the field or greenhouse.

How to Treat Tomato Mosaic Virus?

Since there are no chemical tomato disease treatments for Mosaic Virus, you should mainly focus on preventive measures and cultural practices. Key strategies include:

1. Avoid excessive nitrogen fertilization, especially early in the season when night temperatures are cool. 
2. It’s also helpful to reduce humidity through proper ventilation, spacing plants adequately, and avoiding overhead irrigation can also help. 
3. If plants show symptoms, promptly remove and dispose of infected plants, including roots, to prevent the spread of the disease. 
4. Practicing crop rotation and ensuring good soil drainage can mitigate the risk of future outbreaks.