Tomato Plant Diseases and Prevention and Treatment Methods

Explore tomato plant diseases and discover expert strategies for prevention and treatment to ensure robust, disease-free crops.

At Xu Farm, we’ve compiled information on 16 common tomato plant diseases and their root treatments, providing you with valuable knowledge to ensure the highest productivity and quality in tomato cultivation.

Common Tomato Plant Diseases and Treatment Methods

1. Tomato late blight disease

This is a very common disease in plants of the tomato family, caused by the bacterium Phytophthora infestans. The disease begins with dark green spots resembling water blisters, which then gradually turn black and can cause affected parts to become mushy or brittle, depending on environmental conditions.

The disease occurs and becomes more harmful in conditions of heavy rain, high humidity, alternating rain and sunshine, overcast weather with fog, in low-lying areas with poor drainage, imbalanced fertilizer application, and excessive nitrogen fertilization.

Disease prevention measures:

Before planting, it is essential to clean the field, collect and destroy disease residues, and practice crop rotation to prevent disease recurrence. Apply lime and organic fertilizer before planting. Use balanced fertilizers, increase the application of potassium and phosphorus fertilizers. Construct raised beds with wide furrows for better drainage.

When the disease is detected, various copper-based and fungicidal products containing active ingredients such as Mancozeb, Phosphorous, Fosetyl-aluminium can be used, such as Ridomil Gold 68WP, Aliette 80WG, Eddy 72WP+ Klifos, Agrifos 400, etc.

2. Anthracnose of Tomato

Tomato Anthracnose is caused by the fungus Colletotrichum phomoides. It manifests as initially round, slightly sunken water-soaked spots on the tomato fruit. These spots gradually expand, reaching a diameter of 0.5-0.2 inches (1-5 millimeters), with the center of the lesion turning black or brown and the margins becoming grayish-brown.

The disease tends to be more severe during rainy seasons or in fields with high humidity.

Disease prevention measures:

Choose disease-resistant tomato varieties, plant them with adequate spacing, and use trellises to provide better air circulation around the plants.

Employ drip irrigation to water at the root level, avoiding excessive moisture on the leaves. Harvest tomatoes at the right time to prevent overripening and susceptibility to the disease.

Collect and destroy any diseased fruit to prevent the spread of the disease over a larger area.

When the disease is detected at an early stage, you can apply one of the following fungicides:

Fungicides containing the active ingredient Azoxystrobin, such as Amista. Fungicides containing the active ingredient Metominostrobin, such as Ringo-L 20SC. Other fungicides like Amistar 250SC, Plant 50WP, Antracol 70WP, Polyram 80DF, Daconil 500SC, etc., as per the instructions on the product packaging.

3. Powdery mildew

Powdery mildew is a fungal disease that can be easily identified by the white powdery coating on the leaves and stems of the plant. The initial signs of the disease are very small, scattered spots on the leaf surface. When these spots first appear, they may be light green or pale yellow and are visible on the upper side of the leaves. The fungal spores of powdery mildew tend to develop vigorously on the leaf surface (the upper side). The disease is caused by various strains of fungi, including Leveillula taurica and Erysiphe cichoracearum, and is common in plants of the nightshade family.

Preventive measures:

If you detect the issue early, trim and dispose of all affected leaves, then spray the plant weekly with a mixture of one part milk to five parts water while the mildew is still present. Alternatively, you can use sulfur-based fungicides for treatment and prevention.

4. Bacterial Wilt of Tomato

This is a disease caused by the bacterium Pseudomonas solanacearum. The disease can be detrimental throughout the entire growth period of tomato plants but often causes more damage during the flowering and fruiting stages until the fruit ripens.

Infected plants exhibit wilting symptoms, which can start with the wilting of a single branch or small section, and then the leaves below continue to wilt and droop. Eventually, this leads to the entire plant wilting, collapsing, and dying. The disease typically occurs, develops, and causes severe damage in conditions of high air temperature and humidity, posing significant challenges for farmers.

Preventive and control measures:

• Use disease-resistant tomato varieties and good pest control practices.
• Raise the planting beds to prevent waterlogging during rainfall or irrigation.
• Plant tomatoes at an appropriate spacing to allow for good air circulation.
• Apply balanced fertilization with proper ratios of nitrogen, phosphorus, and potassium. Increase the use of organic fertilizers, lime, and potassium or wood ash.
• Practice crop rotation to minimize the spread of the disease.
• Regularly monitor the plant’s condition, and if symptoms of the disease appear, use Stamer 20 WP or a suitable treatment immediately.

5. Blossom-End Rot

Tomato Blossom-End Rot is a type of disease that can be immediately identified by the discolored skin at the bottom of the fruit, opposite the stem. This is often a sign of calcium deficiency, typically caused by poor or depleted soil due to overwatering.

Preventive measures:

The best approach is to use well-draining soil rich in organic matter and implement a planned irrigation schedule to avoid overwatering.

If your tomatoes are affected by blossom-end rot, select the affected fruits to prevent further spread, then lightly amend the soil with a diluted milk solution (50/50 water and milk) to quickly boost calcium levels. Adding crushed eggshells to the soil at the time of planting is also a common practice and is believed to help prevent the disease.

6. Leaf curl disease

Leaf curl disease, also known as tomato leaf curl, is caused by a virus often transmitted by whiteflies or introduced into your garden through infected plant material. The initial symptoms involve the curling of the leaves inward, followed by a yellowing of the affected foliage. The plant’s growth will become stunted, flowering may decrease, and fruit set may be reduced or cease altogether.

Preventive measures:

The only effective way to manage this disease is to remove and properly dispose of infected plants. However, keep in mind that temporary leaf curling can occur due to inconsistent watering, so rule out this cause before resorting to plant removal.

7. Tomato Plant Diseases – Fruit Cracking

Cracked tomatoes are a clear sign of either overwatering or inconsistent watering. To prevent fruit cracking, water sparingly but regularly, rather than allowing the plant to go from soaking wet to dry. Additionally, mulching the soil surface with organic matter can help retain moisture.

8. Tomato Plant Diseases- Hollow Fruit

While not immediately visible like cracked fruit, hollow tomatoes are another symptom of poor growing conditions. The cause of this condition is often excessive watering or rainfall, extreme temperatures, or high nitrogen levels in the soil. There’s no cure for affected fruit, but with improved growing conditions, tomato plants can still produce healthy fruit in subsequent flowering cycles.

9. Leaf Spot Disease

Leaf spot disease is caused by the bacterium Septoria lycopersici, and it thrives in warm, humid conditions. Dark brown spots first appear on the undersides of lower leaves, gradually enlarging and coalescing over time. Eventually, the infected leaves will drop, severely weakening the plant due to reduced photosynthesis.

Preventive Measures: Remove all infected leaves as soon as you spot them and then spray the remaining parts of the plant with organic fungicides based on copper or potassium bicarbonate.

10. Tomato Blossom-End Rot

Tomato blossom-end rot is caused by the bacterium Clavibacter michiganensis. It begins with small yellowish spots on ripe red tomatoes, which gradually expand, causing the fruit to rot, become soft, and spread to other fruit or plant parts.

Preventive Measures: Regularly monitor and remove infected plants to prevent the disease from spreading widely and impacting tomato plant productivity. Practice crop rotation with various crops to ensure the disease has subsided before replanting tomatoes in the same area.

11. Tomato Catface

Tomatoes affected by Cat Face Disease do not develop normally, exhibiting various deformities, cracks, and holes. There isn’t a single definitive cause, but low temperatures can be a primary factor leading to this condition. Additionally, excessively high nitrogen levels in the soil can weaken the plants and increase susceptibility.

However, this condition does not affect the quality of the tomatoes; they can still be consumed as usual, though their aesthetic appeal is often compromised.

Preventive Measures:

Planting tomatoes at the right time can help minimize the impact of unusual weather fluctuations, ensuring that the plants are not excessively affected by the differences between day and night temperatures.

Tomato Fruit Spot Disease

Tomato fruit spot disease, caused by the Stemphylium sp. fungus, significantly impacts tomato yield and quality.

The initial symptoms include round, sunken brown spots with white or brownish edges. As the disease progresses, the entire spot turns black. Multiple spots can merge to form large, rotting areas on the fruit.

Preventive Measures:

This disease primarily affects tomato varieties with elongated, thin skin. It is advisable not to plant such varieties during the rainy season. Plant tomatoes with appropriate spacing to ensure good airflow, preventing excessive moisture that can lead to disease.

Blossom Drop Disease

Blossom drop disease is a common issue in tomato plants where many flowers are produced but few develop into fruit.

Generally, this condition is mainly caused by temperature fluctuations. Rapid changes in temperature can cause the plant to struggle to adapt, particularly during the flowering phase, resulting in the shedding of many flowers and a reduced fruit set, affecting tomato plant productivity.

Preventive Measures:

There is no single remedy for this condition, but providing optimal nutrition to the plant can help it thrive.

Low Fruit Setting

In reality, even under ideal conditions, tomato plants often have a low fruit set rate, which doesn’t necessarily cause significant harm to farmers. Tomatoes are self-pollinating, and a gentle breeze is often enough for pollination. However, in locations with overhead shelter or challenging growing conditions, plants may benefit from some assistance.

You can take on the role of pollinator by gently tapping the inside of each flower with a brush, using a high-quality paintbrush. Another method is to simulate wind-induced vibrations by gently shaking individual flowers on the plant using an electric toothbrush or lightly shaking the entire plant to aid in the pollination process.

Additionally, if there is an excessive amount of nitrogen in the soil where tomatoes are planted, it may result in lush foliage growth but few flowers. Therefore, it’s essential to balance the nutrient levels in your soil to minimize this occurrence.

Sun Scald Disease

If unripe, green tomatoes are suddenly exposed to direct, intense sunlight, they can develop white blister-like spots that later turn moldy. To prevent this, ensure that your tomato plants have adequate nutrition to produce enough leaf cover and natural shade. However, if necessary, you can temporarily shield exposed fruit with a light cloth to protect them.

Tomato Plant Diseases: Nutrient Deficiency

Lastly, nutrient deficiency has a more severe impact on tomatoes than most other crops. Various symptoms may manifest, but generally, the leaves will turn yellow, pale, or even dull, and in severe cases, the plants may wither and die.

Effective soil management through the use of various supplemental organic matter is the best way to prevent this issue from arising in the first place.

Tomatoes are an incredibly nutritious fruit; however, their development can be plagued by various problems that affect both yield and quality. Therefore, create the best possible growth conditions and address any issues promptly to produce the highest quality tomatoes.