Fungal diseases affecting tomatoes

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Tomatoes have a very special place in Indian cuisine. They add flavor and umami to a wide variety of foods across the globe. Tomatoes are rich in Vitamin C, Vitamin K, and potassium, which are known for their impact on reducing heart diseases and lowering risks of cancer. But there are certain tomato pests and diseases that limit their production.

Tomatoes can develop two kinds of diseases; namely contagious and non-contagious diseases. Contagious diseases are caused by infectious micro-organisms like fungi, viruses, and bacteria. These diseases can spread rapidly in favorable conditions from one plant to another. 

On the other hand, non-contagious diseases are caused by non-infectious factors such as chemicals or harsh environmental, nutritional, and genetic factors. As evident from the name, diseases caused by them are not rapidly transmissible. But one major threat of these diseases is that they spread quite extensively over the entire field if the environment is not favorable for planting.

fungel diseases affecting tomatoes

Fungal diseases of tomatoes

Fungal diseases are a major limiting factor in tomato production. Fungi feed and live on the infected tissues. Fungal diseases spread through spores, which are microscopic entities and can be easily transmitted from one plant to another by mechanical means like winds, water, splashes, etc. These spores infect healthy plants, and they develop certain symptoms like leaf wilts, spots, and holes. These symptoms lead to premature defoliation, causing a major fall in tomato production. There are certain factors that help fungal diseases spread faster, such as rainfall, humidity, temperature, and free moisture. 

Below is a list of some of the most common fungal diseases of tomatoes.

  • Anthracnose
  • Fusarium Wilt
  • Septoria leaf spot.
  • Early Blight
  • Late Blight

1. Septoria Leaf Spot

Symptoms of septoria leaf spots, as the name indicates, are small circular spots on leaves that are grayish-white in the center and have dark corners. Infected leaves wither and fall off after turning yellow. Warm and wet seasons promote the spread of this disease, and water splashes transmit the spores from infected leaves to healthy plants.

2. Anthracnose

This disease also develops small circular patches on tomato fruits. Afterward, fungal rings form around the primary spot. Tomato pulp, especially the overripe ones, can completely rot. Therefore, it is advised to pick the tomato fruits as soon as they are ripe. The spores of anthracnose are also spread by water splashes, and the disease occurs in wet and humid seasons.

3. Fusarium and Verticillium Wilt

These fungal diseases attack the roots of the plants through the soil and then block the water-carrying vessels of the plants. In this way, they hinder the water supply to the plant, and without enough water, it starts to wilt. Top or lower leaves first suffer wilting and then they lose color and die. Tomato wilt is a viral disease. This disease keeps on progressing until the whole plant is infected.

To prevent this disease from spreading, it is advised to avoid growing tomatoes in the same fields where tomato wilt occurred for about 4-5 years because this fungus can remain in the soil for a long period without infecting a new host.

4. Early Blight (Alternaria)

Another fungus called Alternaria causes early blight in tomatoes. The spots on the lower plant leaves are like targets, with a black core and bold, dark edges. It attacks the stem area of tomatoes, and they develop large, indented areas surrounded by circular rings. It attacks the plant after the fruits are produced.

5. Late Blight

Tomato late blight is caused by a fungus called Phytophthora infestans. It is a very fast-spreading fungal disease and occurs in the cold, rainy seasons. Its symptoms are irregular green splotches on the leaf that look like frost damage. Fruits develop big brown irregular blotches that quickly rot. Potatoes can also develop this disease and transfer to tomatoes.

Control of tomato fungal diseases.

Tomato fungal diseases can be controlled in a variety of ways. In the following passages, I will briefly explain some easy strategies to avoid and control these diseases.

  1. Proper sanitization of the soil helps prevent the fungal spores from infecting the next yield. Tomato refuse should be removed and discarded completely and burned in the compost pile. The temperature of the compost pile must be very high to eliminate the spores from the soil. Then bury the residue properly to keep the leftover spores beneath the soil and prevent them from further attacking the tomato crops.
  1. The use of fungicides is at the core of the treatment of fungal diseases. They should be used before the plant develops the disease. Fungicides can be used as a part of an integrated pest management program (IPM). Keep on applying fungicides as long as the conditions are favorable for the spread of fungi and the target pathogen is not completely removed.
  2. Another very useful technique to control tomato fungal disease is crop rotation. In this technique, tomatoes are planted in different fields away from the previous crop’s location. Crops should be rotated for at least 3 years to avoid the attack of soil-borne fungal diseases.
  3. The second line of defense against leaf spot diseases is to alter the microclimate surrounding tomato plants. Fungi thrive in moist, humid conditions, in particular on leaves that remain wet for long periods of time. Tomatoes should be grown in full sun with good air circulation to dry the leaves. Staking or caging tomatoes brings the plants up off the soil and allows more rapid drying of the plant.
  4. Watering should be done in the morning to allow sufficient drying time. The use of a soaker hose to irrigate completely eliminates regular wetting of the leaves.
  5. Cover crop mulches such as composted leaves or straw mulch can be placed on the soil surface to help reduce soil-borne fungal diseases such as Buckeye rot and Anthracnose fruit rot by keeping developing fruit from coming into direct contact with the soil surface. The soil beneath and surrounding the tomato plant should be covered with at least 6 inches of mulch early in the tomato season. Mulching tomato plantings this way may also reduce weeds and prevent loss of soil moisture during the growing season.


Juicy, perfectly sun-ripened tomatoes are among the easiest vegetables you can grow in your garden. But taking good care of your tomato plants means keeping an eye out for diseases caused by fungi, bacteria, and viruses, which can cause leaf spots and blights. Temperature, nutrient levels, and moisture levels can also cause problems, potentially ruining your harvest and your dreams of enjoying slices of homegrown tomato on your next BLT. You can keep these potential problems at bay by familiarizing yourself with their symptoms and using a few simple strategies. With a little effort on your part, your plants can stay healthy and productive all season long.


1. How do I know if my tomato plant is diseased?

Identify: Appearing as tiny, round splotches on the leaves, this tomato disease (Septoria lycopersici) typically starts on the lowest leaves first. The spots have dark brown edges and lighter centers, and there are usually many spots on each leaf. Infected leaves eventually turn yellow and then brown, and fall off.

2. How does baking soda help tomato plants?

Its alkaline properties are the key. By spritzing a baking soda solution on your tomato plants, the surface becomes more alkaline, creating an unsuitable environment for blight to take hold. You’ll prevent any blight from growing or stop any spread dead in its tracks.

3. How often should you spray tomatoes with fungicide?

It can be used as soon as tomato plants are subjected to humid or rainy conditions that can cause blight. Premixed and concentrated chlorothalonil are available, and spraying it every seven to 10 days is ideal for the prevention of blight. It can be used at any time before harvesting tomatoes.

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