Diseases of tomato seedlings: description with photographs and methods of treatment

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Published: 06/09/2019

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You can get a good harvest of tomatoes if you follow all the rules without exception, starting with planting seeds for seedlings. If the seedlings turn out to be weak or, worse, sick, then a generous tomato harvest is out of the question.

What are the main diseases that tomato seedlings suffer from? We have prepared a brief description with photographs of common diseases of tomato seedlings and simple and effective methods of treating them.

These diseases can be divided into several categories.

1 Fungal diseases
2 Rot
3 Viral diseases
4 Bacterial diseases
5 Non-communicable diseases
6 Preventive measures
7 How to treat tomato seedlings against pests?

Fungal diseases

These diseases often occur due to improper care. Water the seedlings regularly, but moderately. Do not allow the soil in the container to flood.

If the sprouts are located too close to each other, this leads to poor air circulation between them, and a fungal disease occurs.

The room where tomatoes grow should be as comfortable as possible for the development of sprouts: light, warm, not damp.

— Late blight manifests itself by the appearance of dark spots on the leaves. Soon the affected leaves begin to wither and fall off. Immediately tear out such sprouts and burn them. Treat the remaining sprouts with Zaslon. After two weeks, the seedlings will have to be treated again, but with the Barrier preparation.

To fully ensure that late blight does not occur on the tomatoes again, treat them again with a garlic-manganese solution. Dissolve 1 gram in a bucket of water. manganese and add garlic juice obtained from squeezing a glass of garlic cloves.

Blackleg attacks the stems of tomato seedlings. They become thin, the sprout does not receive life-giving moisture from the soil and soon dies. Remove diseased plants from the cup.

To avoid this disease, some gardeners add a little sifted wood ash and copper sulfate to the soil before planting seeds.

— White spotting is caused by fungal spores. White spotting initially manifests itself by the appearance of black dots on the lower leaves of the sprouts. Without taking immediate action, the disease quickly spreads throughout the plant.

Later the leaves turn black and fall off. If the disease is detected early, the seedlings can be completely saved by treating them with a solution of copper sulfate. Those sprouts that could not be saved should be pulled out and burned.

— Fusarium wilt is caused by a soil fungus. It attacks the roots of plants and causes them to wilt.

If you cut the stem of an affected plant, you will see some brown tufts. This is a manifestation of Fusarium wilt. The disease occurs from insufficient lighting in the room where tomatoes are grown, or from improper care of them.

Bronzing

Spots on tomato seedlings can also have a viral etiology. Bronzing is one of these diseases. It appears as large green-yellow spots on the leaves of the plant. The spots merge with each other, forming streaks. The leaves curl into a tube, dry out and fall off.

Cause

Tomato bushes become infected through insect pests (thrips) or through weeds.

Control measures and prevention

The main prevention is weeding and destruction of weeds and the extermination of harmful insects.

Bronze spots on tomato seedlings cannot be treated, but when the temperature rises to 45 degrees, their development stops.

Rotten

Rotting of tomato sprouts occurs from too low ambient temperatures or from excessive watering. The first sign of the disease is a change in the color of the leaves of the seedlings. Later, mucous spots with a fungal coating appear on them.

As soon as you notice a change in the color of the leaves, immediately reduce watering and bring the air temperature in the room back to normal. Spray the tomato seedlings with a solution of copper oxychloride, but first pick off all the affected leaves. After two days, treat the tomatoes with a two percent solution of trichodermin.

NOTE: Steaming the soil before sowing seeds can prevent the development of white rot.

— Cladosporiosis most often occurs in the first days after planting seedlings in open ground. Cladosporiosis begins with the lower leaves, yellow spots appear on their front side, and a coating forms on the back. A little later, the leaves curl into tubes, bend, wither, and crumble.

Often the disease affects tomatoes at the flowering stage. The cause of the disease is too high ambient temperature with high air humidity. Greenhouse tomatoes suffer from this disease more often than ground tomatoes.

Plants can be saved if you tear off the affected leaves in time and treat them with a one percent solution of Bordeaux mixture or ready-made “Barrier” or “Barrier” products.

- Dry rot, or Alternaria - with this disease, brown spots form on the lower surface of the leaves.

Gradually they grow and cover the entire surface of the leaves. As a result, they fall off, and the disease begins its destructive spread along the tomato stems. If dry rot is detected early, seedlings can be saved using the fungicidal preparations Ditan, Acrobat or Quadris.

— Fomoz, or brown rot, can appear after fruit set. First, a brown spot appears on the stalk, then it begins to increase in size, and the fruit rots from the inside.

Phoma occurs from excess nitrogen in the soil and high air humidity. To save the tomato plantation, pick and destroy all affected fruits, and treat the plantation with Zaslon, Fundazol, Oksikhom or Bordeaux mixture.

— Powdery mildew often affects tomatoes. It is caused by marsupial fungi, the spores of which live in the soil.

Usually, powdery mildew affects tomatoes in the first days after planting seedlings in the ground. The initial signs of the disease are a white coating on the leaves. Without taking rescue measures, plants will inevitably die. The products “Quadris”, “Topaz” and “Strobi” can save the crops. They can also be used to prevent powdery mildew.

Pests of seedlings

Normally, young plants kept at home should not have any pests. If they appear, it means that the gardener has grossly violated agricultural technology and the rules for maintaining tomato seedlings.

If pests, despite the taken preventive measures, still appear, you need to get rid of them as soon as possible, otherwise the seedlings will die.

Thrips

These small pests belong to the group of ancient insects. In Russia, out of 2 thousand species of thrips, 300 are found. The pests have an elongated, pointed body 0.5-1.5 mm long. These nimble insects can be brown, gray, greenish, or black. It is very difficult to see them on the leaves.

Thrips suck juices from plants, starting from the tops. Within a few days, the seedlings lose their healthy appearance, and the leaves become light. Pests multiply very quickly and are capable of destroying entire seedlings in a matter of days.

To prevent thrips, it is recommended to use garlic tincture:

Chop a few heads of garlic.
Dilute the garlic pulp with water - take 200 ml of water for each tablespoon.
Leave the solution for about 3 hours.
Strain the tincture through cheesecloth.

Use a spray bottle to spray seedlings.

If insects have already appeared on the seedlings, standard insecticides are used. It is sprayed with Actellik, Fitoverm, Karate or their analogues in the dosage specified by the manufacturer.

Whitefly

This butterfly reaches a length of only 3 mm and is the most dangerous pest for tomato seedlings. She and her larvae drink plant juices, which, merging, form a white coating on the leaves. The insect reproduces extremely quickly and can kill a plant within two days.

How to fight:

spray the seedlings with the insecticide Phosbecid;
briefly lower the temperature below +10°C - the whitefly dies when it gets cold (the method is suitable for greenhouse conditions);
spray with a soap solution - rub a bar of soap on a coarse grater and dilute it in 10 liters of water;
treat with tobacco infusion - 100 g of dry tobacco is poured into 1 liter of water, after 2-3 hours the volume is adjusted to 3 liters and the plants are sprayed.

The whitefly not only harms tomato seedlings by drinking their juices, but also infects them with sooty fungus, which causes the leaves to turn black.

Aphid

These are small, soft-bodied insects that settle on plants and suck the juices from them. They reach a length of 0.5-1 mm. Aphids can be winged or wingless, depending on the stage of development. On tomatoes, it is most often found in red or green.

Leaves affected by aphids first turn yellow and then dry out. To fight, they use different means - chemical, folk, biological and even mechanical.

Fighting methods:

washing off insects with water;
spraying tomato leaves with infusion - two cups per 250 ml of crushed leaves, pour 0.5 liters of water;
treatment with fungicides - Actellik, Fufanon, Alatar, Fitoverm, Aktara.

The latter method begins to act after 4-6 hours, but then protects the plants for a whole month.

Viral diseases

Often seedlings are exposed to such diseases due to infected seeds. No matter how beautiful the seeds look, they still need to be treated with a weak solution of potassium permanganate before planting.

The second cause of viral diseases is a lack of nutrients in the soil. For this reason, the sprouts turn out weak and cannot resist even the weakest infection.

What are the types of viral diseases of seedlings and how to treat them?

— The mosaic affects tomatoes in the first days after planting seedlings in the ground.

Initially, the color of the leaves changes, then they curl and fall off. Most often, the virus is transferred to seedlings along with seeds that the gardener was too lazy to disinfect. Tear up sprouts infected with the mosaic virus by the roots and burn them. Disinfect the soil under them with a weak solution of manganese and powder with wood ash. For prevention, spray healthy plants with a five percent urea solution or a weak solution of potassium permanganate.

— Aspermia, or seedlessness, is manifested by very slow growth of seedlings.

On mature plants there are no seeds in the twisted fruits, the leaves are too small. Unfortunately, there is no medicine to treat aspermia yet.

- Streak - brown streaks appear on the leaves.

Later, ulcerative inflammations form in their place. This causes tomato seedlings to become brittle and the top leaves begin to fall off. There is also no cure for this disease, so the affected plants are simply destroyed.

White plaque and white spots

We are used to fighting powdery mildew on cucumbers or gooseberries, but it also happens on tomatoes. Small white spots and the familiar whitish coating all over the leaf are caused by three different pathogens. The good thing is that you can fight all three in one fell swoop.

How it manifests itself:

Most often, spots and powdery coating are observed on late varieties of tomatoes in greenhouses. If the development of the disease is not stopped in time, it quickly moves from leaves to shoots and sepals. Subsequently, the fungus causes the plant to gradually dry out until it dies.

Conditions for active development:

Powdery mildew manifests itself in the second half of summer. Unlike other fungi, its pathogens are active at fairly low humidity and high temperatures (from +20°C to +25°C). Therefore, during drought, abundant watering directly over the leaves is recommended.

What to spray:

To combat powdery mildew of tomatoes from chemical fungicides, Strobi, Teovit Jet, Ordan, Quadris, Privent are suitable. Among biological products, Pseudobacterin, Fitosporin M, Baktofit, Alirin B, Gamair are successfully used.

Bacterial diseases

These diseases can also occur as a result of poor soil and improper care of seedlings. Poor quality seed material can also cause bacterial infection.

— Brown leaf spotting can occur due to excessive watering or too damp ambient air.

Infection is manifested by the appearance of brown spots on the upper surface of the leaves. A coating appears on the lower surface, which soon acquires a reddish tint. There is no cure for this bacterial disease. Sick specimens are destroyed, and the ground under them is disinfected. The remaining plants are treated against infection with a one percent solution of copper sulfate.

— Black spot bacteria infect seedlings through the soil or seeds.

The disease develops rapidly when the ambient temperature exceeds 25 degrees, while the air humidity is high. Interestingly, a subsequent decrease in temperature does not have a negative effect on the bacteria; the disease only progresses. Bacteria die only at a temperature of 56 degrees.

Black bacterial spot is manifested by the appearance of black spots bordered by a yellow stripe on the leaves. Over time, black stripes appear on the stems of tomatoes. As a result, the sprouts quickly die.

There is no cure for this disease. Destroy the affected sprouts and treat the rest with Hom.

— Stolbur, or phytoplasmosis. The carriers are insects.

Stolbur manifests itself as lilac or violet spots that appear on the leaves and stems of seedlings. Fortunately, this disease can be treated with the drugs Confidor or Aktara. These funds can also be used to prevent the disease. Spray the seedlings for the first time a month after sowing the seeds, and the second time before planting in the soil.

— Bacterial canker is fatal to seedlings and cannot be treated. It manifests itself by the appearance of ulcerative lesions on the leaves and stems. Sick seedlings should be immediately destroyed and the entire soil in the container replaced.

To prevent bacterial cancer, an aqueous solution of formaldehyde prepared in a ratio of 1:300 is used.

— Bacterial mottling can occur due to mechanical damage to the leaves or stems of seedlings.

The symptom of the disease is the appearance of dark yellow spots on the leaves. Affected leaves curl into tubes and fall off. To save the plantings, tear off all affected parts of the seedlings and treat them with a weak solution of copper sulfate.

How to treat leaf burns

The appearance of such spots was necessarily preceded by changes in the usual regime. Usually this means taking the seedlings outside or transplanting them to a new location. To eliminate the risk of such manifestations, it is advisable to accustom the seedlings to sunlight gradually, using local darkening and regular watering. This link will tell you about the treatment of brown spots on grape leaves.

Watering, by the way, can also serve as a negative factor. If you water tomatoes in hot weather, every drop that falls on the leaves of the plant becomes a miniature lens, literally burning a hole in the shell. That is why it is best to water in the evening, treating exclusively the root area. The same rule can be extended to spraying, which must be carried out in dry weather and in the evening, so as not to burn the leaves and stem of the plant being treated.

You can fight sunburn only by strengthening the plant’s defenses. If there is significant damage, there is no point in nurturing such seedlings, because such a situation will adversely affect productivity.

Video shows how to treat leaf burns:

In addition to the sun, the plant can also suffer from heat stroke. For example, if you use too cold water when watering. The soil heats up during the day and forms steam when moisture enters. It burns the leaves and can also cause the stem of the plant to literally cook.

The second possible option: increasing the temperature in the greenhouse. That is why it is necessary to take care of good ventilation in advance, otherwise overheating of the plants cannot be avoided. Here, too, it is best to take reasonable measures before such a problem arises, because such conditions cannot be treated.

Non-communicable diseases

Such diseases arise from improper feeding of seedlings. As a result of errors, sprouts receive an excess of some useful substances and a deficiency of others. Weakening of plants leads to diseases.

More often, such diseases occur from a lack of nitrogen, copper, calcium, potassium phosphorus or other microelements in the soil. However, if feeding the seedlings is done strictly according to the instructions, then there cannot be any imbalance in the content of nutrients in the soil.

With insufficient nitrogen, the leaves of the seedlings become paler. The situation can be corrected using a urea solution.
Due to a lack of phosphorus, dead areas appear on tomato leaves, and the leaves themselves acquire a purple tint. In this case, brown dots form on the lower surface of the leaves. Superphosphate and ammonium sulfate allow you to replenish phosphorus in the soil.
When there is a small amount of copper in the soil, the leaves first bend, then curl and change color to light gray. You can normalize the copper content using a three percent solution of copper sulfate.
Lack of calcium in the soil leads to the death of the lower leaves. The upper leaves remain completely healthy. The soil needs to be fertilized with a solution of calcium nitrate.
With a lack of iron, the leaves become discolored and small spots appear on them. It is necessary to immediately add a 0.25% solution of iron sulfate to the soil.
If you notice that the leaves of the tomatoes have begun to dry out along the contour, this means that you need to enrich the soil with potassium. This is best done using an infusion of wood ash.
Due to a lack of sulfur in the soil, the leaves of the seedlings turn pale pink. The problem can be eliminated using a three percent solution of magnesium sulfate.

Reasons for appearance

Having noticed white spots on tomato leaves, any gardener must urgently take measures to eliminate this phenomenon. First of all, it is necessary to identify the causes. They can be divided into two groups, and after making a “diagnosis”, treatment can be carried out.

Why did the spots appear:

Sun or heat burn.
Fungal diseases.

In the first case, the location of the spots is the upper tiers of leaves. Diseases most often initially affect the lower parts of the plant, spreading higher over time. More details about this, as well as methods for treating and preventing such ailments are described below.

It may also be useful for you to learn about how tall tomatoes are grown in open ground.

In the video - why white spots appear on the leaves of seedlings:

Preventive measures

Make it a rule to never buy seeds from random sellers.
Before planting, disinfect all seeds with solutions of manganese or copper sulfate. Other ready-to-use preparations are also sold for these purposes.
If you prefer to use store-bought soil for seedlings, make sure that the packaging is intact. If you prepare the soil mixture yourself, then do it strictly according to the rules. Mix the soil mixture thoroughly, be sure to sift and disinfect. This can be done by calcining the soil in the oven at a temperature of 100 degrees. A good disinfectant is a hot solution of potassium permanganate.
Before planting seeds, be sure to disinfect the seed and soil in the container.
Use only zoned seed varieties for growing seedlings.
In the room where containers with seedlings are located, maintain optimal temperature and humidity.
If a disease is detected, immediately take the cup with the sprout away from the rest of the seedlings.
Do not neglect preventive measures to protect tomatoes from diseases.
Never plant seedlings in the ground in the same place twice in a row.