Tomato diseases: recognize and eliminate | Instructions with pictures

Tomatoes are very popular in small gardens and for self-sufficiency, as they promise a rich harvest from a relatively small area. In return, however, they require good care in the best possible place. Nevertheless, tomato diseases, animal pests or physiological disorders repeatedly prevent the expected abundance of harvest. However, timely intervention is often successful.

How do I recognize a pest infestation?

Animal pests always leave traces on your tomatoes, even if some of the little animals cannot be seen with the naked eye due to their size. White spots, thin threads, a sticky coating or black droppings can be the first signs. With all animal pests, it is important to detect an infestation at an early stage. Only then is combating a promising outcome and the harvest still salvageable.

Possible symptoms of a pest infestation:

  • Whitefly : sticky coating on leaves and fruits, white insects on the underside of the leaf (about 2 mm in size)
  • Spider mite : thin spider threads on the leaves and shoots, slight yellowing of the leaves, withered leaves in severe infestations
  • Thrips/ Thrips : black droppings, white spots on leaves and fruit
  • Tomato leaf miner: tortuous leaf miners (light lines) on leaves
  • Tomato rust mite : drying shoots, leaves and flowers, corked skin of young fruits

How can I successfully combat animal pests?

Of course, in principle you can use chemical agents for pest control, but this is not recommended, especially for crops. You always have to take into account that residues remain on the plants and possibly also accumulate in the fruit. Being free of harmful substances is often a key reason for self-supply with vegetables. Many pests can be fought with so-called beneficial insects or predatory insects.

You can use predatory insects very well against thrips. Lacewing larvae or predatory mites do the work for you without damaging the plants or making your tomatoes inedible. Spider mites are also destroyed by predatory mites. However, hosing down the tomato plants with a powerful jet of water can also help here. Make sure that the leaves can dry quickly! Moisture promotes infection with various fungal diseases.

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You can also fight the whitefly and the tomato leaf miner with the help of predatory insects, but the parasitic wasp is recommended here. An infestation with tomato rust mites is usually recognized so late that it is almost impossible to combat it. Remove the infested plants immediately so that the mites cannot spread to the neighboring plants.

How do I recognize fungal diseases in my tomatoes?

Unfortunately, fungal diseases in tomato cultivation are not uncommon. There are numerous different pathogens that occur frequently at different times. Each fungal infection shows different symptoms. What they all have in common, however, is that only quick recognition of tomato diseases and rapid intervention can save your plants and the harvest.

Common fungal diseases in tomatoes:

  • early blight
  • fruit and stem rot
  • Grauschimmel
  • Korkwurzeln
  • Late blight and late blight
  • Powdery mildew (powdery and downy mildew)
  • velvet spot disease

early blight

This infection is the most common fungal disease in tomatoes and is not easy to combat. The infestation usually begins between June and August in the lower part of the plant and slowly rises to the top. Black spots appear between the leaf veins before the leaves curl up and fall off. Affected fruits become soft, they rot and mold. If the location is too warm and too humid, then transplanting will help. The affected plants are also treated with a fungicide to prevent the spread of the pathogen.

fruit and stem rot

The spores of Didymella lycopersici, responsible for fruit and stem rot, are spread by wind and rain. Wounds and stem attachments are the portals of entry. At the beginning of the disease, the bark tissue in the lower part of the tomato plant turns black, later the leaves turn yellow. The fruits turn dark and eventually begin to mold. The fruit and stem rot is treated like the early blight.


Gray mold, also known as ghost spot disease, can appear from May to September. It attacks the whole plant and prefers high humidity. Therefore, it is often found in greenhouses. React at the first gray spots on the leaves before your tomatoes start to go moldy. Cut back all affected parts of the plant down to healthy tissue and discard moldy fruit. Heavily infested plants should be disposed of completely, but not in the compost. There, the fungal spores can survive and spread further.

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The cork roots do not belong to the specific tomato diseases, they can also occur in other plants such as cucumbers, peppers or aubergines. Unfortunately, the disease often persists for several years if the pathogens survive in the soil. Therefore, ideally, tomatoes should not be grown in the same location every year. The corky appearance of the roots occurs especially in hot weather and drought. The tissue later disintegrates. Soil improvement and sufficient watering make sense.

Late blight and late blight

Late blight (Phytophthora infestans) occurs almost exclusively in tomatoes grown outdoors and is transmitted by the wind. High humidity and moderately warm weather (approx. 18°C ​​to 20°C) contribute to the rapid spread of the infection. Affected tomatoes should no longer be eaten. They get hard brown spots that later turn black. If moisture persists, a grey-white coating forms on the leaves before they die. Fighting with fungicides is only promising in the early stages.

powdery mildew

Powdery mildew is also widespread on tomatoes. If left untreated, it can lead to the death of the plant. Powdery mildew usually occurs between May and August. The leaves and petioles are usually affected. Sticky white spots on the upper sides of the leaves are increasingly merging and growth is disrupted. Later the leaves turn yellow and dry up. Before resorting to a fungicide, try an ecological treatment with concentrated soapy water. Spray affected plants several times at intervals of a few days with this lye.

velvet spot disease

The velvet spot disease is more likely to be observed in greenhouse or foil tomatoes, so it is less common outdoors. Fuzzy, pale yellow spots on the upper side of the leaf and a brown, velvety coating on the same spots on the underside of the leaf are the characteristic symptoms. The affected leaves later die off.

What physiological disorders are there in tomatoes?

Physiological disturbances can also occur in tomatoes. However, these are not counted among the tomato diseases because they are not caused by pests or fungal diseases. Heat, cold, the genes or the supply lead to different types of damage to the fruit and/or plants.

Possible physiological disorders in tomatoes:

  • cracked fruit
  • curled leaves
  • yellow- or green-collared
  • cold damage
  • calcium deficiency
  • Magnesiummangel
  • nose formation
  • sunburn
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How do I recognize and combat deficiency symptoms?

Calcium and magnesium deficiencies are the most common in tomatoes. Both deficiencies are fairly easy to spot. Calcium deficiency leads to what is known as blossom end rot. Watery spots form on the blossoms of the fruit, which later turn brown-black.

Magnesium deficiency shows up in the leaves of your tomato plant. The leaves turn yellow while the leaf veins remain green. This happens mainly in the lower and middle part of the plant. The leaves later dry up.

Overheating and excessive exposure to the sun can lead to yellow or green collars in the fruit. The affected areas at the base of the stem are clearly demarcated from the ripe fruit and the flesh remains hard. Potassium deficiency, too much nitrogen and also too much exhaustion (removal of the excess side shoots) are further causes of this physiological disorder.

With a balanced supply of water and nutrients, you should be able to get deficiencies under control quickly. Regular watering and special tomato fertilizer are helpful here. After a soil analysis, you can also increase the pH value if your soil is too acidic for tomatoes.

How can I prevent tomato diseases in the future?

The best prevention against all types of tomato diseases is careful choice of location and proper care. Although tomatoes require quite a bit of water, too much of it in the wrong place can cause damage. The leaves and fruits should always remain dry, as they are very susceptible to fungal spores. Rain and watering from above should therefore be avoided. A good supply of nutrients also protects against many tomato diseases. Regular fertilizer is therefore recommended.

Plant your tomatoes in a sunny spot or in a greenhouse so they get the warmth they need to grow and ripen. Good ventilation is very important when growing tomatoes in a greenhouse. Humidity should stay below 70 percent if possible. Since some fungal pathogens are also attracted to potatoes and spread by the wind, potatoes should not be planted near tomatoes.

Strong and well cared for plants are much more resistant to pest infestation and tomato diseases. Tie the main shoot of your tomato plants to a stake and remove unwanted side shoots regularly. To prevent transmission of germs, disinfect all plant stakes once a year. You can do this either before or after each season.

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