Why yellow spots appear on tomato leaves in a greenhouse and how to save your tomato harvest

Gardeners often encounter yellowing of tomato foliage. There are many reasons for this phenomenon; it is important to correctly identify the source of the problems in order to preserve the plants. Stains can affect the harvest, or even destroy it altogether.

Why yellow spots appear on tomato leaves in a greenhouse, how to determine the cause and what methods can be used to eliminate it - you will learn all this from our article, supplemented with explanatory photographic materials.

Possible causes of yellowing leaves

Yellowing of leaves is a common phenomenon both indoors and outdoors. Why do the stems and foliage of tomatoes turn yellow? A change in the color of the tops can be caused by errors in care, diseases or an imbalance of substances in the soil.

When yellowing appears on the leaves, do not panic - it is important to quickly and correctly identify the source of the problem.

Lack of fertilizers

Lack of nutrients negatively affects the condition of plants. To correctly determine which substance is too little, you need to pay attention to which part of the plant the yellowing began.

What happens when there is a deficiency of specific elements:

1. Nitrogen. If there is a shortage, the tops turn yellow or discolored. Young leaves grow small, and the plant itself weakens. Lack of nitrogen also negatively affects fruits.
2. Phosphorus. The appearance of yellow spots on the lower leaves is also characteristic of a lack of phosphorus.The leaves become smaller, their edges curl, and the stem takes on a purple hue.
3. Potassium. The lower leaves of the seedlings turn yellow, curl and die, and the stems become stiff. Changes begin from the edges of the leaf plate, new leaves grow small and thick.
4. Zinc. In addition to yellow spots, brown and gray blotches appear on the foliage. Over time, the leaves die off.
5. Magnesium. The foliage color changes to yellow between the veins. New leaves curl inward, and old ones become covered with brown spots and fall off.
6. Bor. The upper leaves become covered with yellow spots, the veins turn brown. The plant grows in width and sheds flowers.
7. Sulfur. First, the upper leaves turn yellow, then the changes affect the lower branches. The tops become brittle and brittle.
8. Iron. Yellow spots appear in the middle of the leaf blade and along the veins.
9. Manganese. Yellowness appears in the middle of the leaf; near the veins, the color of the spots is heterogeneous, yellow-green.
10. Molybdenum. The first pair of true leaves turn yellow and curl upward. The color change begins with the appearance of small yellowish spots, then covering the entire surface of the plate. The leaf veins remain green.

Root damage

The root system is responsible for feeding the entire plant. Its damage negatively affects the foliage.

A change in the color of the tops can be caused by a depressed state of the roots, which occurs for various reasons:

• damage pests;
• weakening due to excess vegetative mass;
• transplant injuries;
• deep loosening of the soil;
• poor quality seedlings.

Most often, yellowing of foliage is caused by a weakening of the root system, which cannot cope with the nutrition of the tops.The result is starvation and leaf death. The color change of the tops begins from the bottom of the plant.

Important! The problem will resolve itself as soon as the damaged roots grow back. The exception is the beginning of the rotting process, in which case treatment with fungicides will be required.

Often the reason for insufficient development of the root system is poor-quality or improperly prepared seedlings. The plant was grown in small containers, which constrained the roots. Such plants have abundant green mass, elongated upward. After the transplant they often get sick.

Sunburn

Lighting plays an important role in seedling growth. Excessive sunlight can cause foliage to burn and turn yellow. This usually happens during a period when the plants are weakened after being planted in the garden.

The tops may also turn yellow due to lack of light. Thickening of plantings leads to the fact that plants do not receive enough light. As a result, the lower and middle leaves begin to change color and fall off.

Excess moisture

A lack of moisture, as well as its excess, negatively affects the health of tomatoes. In case of insufficient watering plants begin to save moisture, trying to reduce its evaporation. In this case, the leaves are rejected.

When there is a lack of moisture, the leaves first curl, then their color changes and they fall off.

With abundant watering, the plant forms excess green mass, the nutrition of which the roots cannot cope with. This leads to insufficient development of the root system and poor absorption of nutrients from the soil. Yellowing of foliage with excess moisture occurs due to a lack of nitrogen.

Plants grown in a greenhouse or greenhouse may turn yellow due to high humidity.The optimal humidity level is 60-70%; as the indicator increases, the tops begin to rot. The situation may be aggravated by low air temperatures.

Pests

Insects can also cause tomato leaves to turn yellow and die:

• whitefly;
• aphid;
• tobacco thrips;
• Colorado beetle.

Possible diseases

Yellowing of foliage is the first symptom of many diseases.

Diseases that cause yellowing of tops:

1. Chloratic curl - the plant droops and looks weakened, the leaves turn yellow and the roots rot.
2. Cladospirosis - a dark coating appears on the lower part of the bush, which turns yellow over time. The spots spread throughout the plant, and the damaged areas die off.
3. Septoria - the lower old leaves are affected first. A small spot appears on the plate, which gradually grows, acquiring a dark outline. The leaves dry out, the stem turns yellow, and the plant dies.
4. Mosaic - the leaf acquires a heterogeneous yellow-green color, deformation of the leaves and fruits occurs, and then their necrosis.
5. Powdery mildew - small yellow spots and white coating appear on the leaves. As the disease progresses, the formations become covered with a damp substance, the fruits crack and rot, the flowers turn black and fall off.
6. Gray rot - the stem becomes covered with gray-brown spots, light stripes appear on it, the leaves turn yellow.
7. Late blight - a white coating appears on the underside of the leaf, then brown oval spots form on the damaged areas, which then spread to the stem. At the same time, the fruits turn black.
8. Brown spot - yellow spots appear on top of the leaf blade, and brown spots on the bottom. The disease develops from the lower branches, gradually affecting the entire tops.
9. Alternaria blight - the leaves turn yellow, black spots appear on them, tissue necrosis occurs and the tops die. Blackened areas form on the fruits.

Yellowing of leaves on seedlings

The leaves of young plants may begin to turn yellow due to natural reasons. Transplanting seedlings from pots to garden beds is stressful for the plants. Yellowness on the leaves indicates the adaptation of tomatoes to new conditions. This happens due to a temporary failure in the supply of nutrients from the root system to the tops. To maintain viability, the plant rejects the lower leaves.

If the problem is caused by planting stress, only the lower leaves will be affected by the color changes. After a few days, the leaves should fall off; if this does not happen, they are removed manually.

Other reasons for yellowing seedlings:

• small container;
• watering errors;
• hypothermia;
• nitrogen deficiency;
• insufficient lighting;
• soil acidification.

Important! Solanaceae are characterized by the death of the lower leaves. If the yellow spots have not started to spread throughout the plant, there is no cause for concern.

Fighting methods

What to do if spots appear on tomatoes? Since there are many problems that cause yellowing of tomato foliage, it is important to correctly identify the source of the problem and eliminate it. If the tops have turned yellow due to illness, you should not leave things to chance. Diseases are treated with chemicals and folk remedies.

Chemical and biological agents

Fungicides are effective against most tomato diseases.

The following drugs are used in treatment:

• "Abiga Peak";
• "Barrier";
• "Ordan";
• "Bravo";
• "Thanos";
• "Ditan";
• "Revus";
• "Quadris";
• "Consento";
• "Fitosporin";
• "Fundazol";
• copper sulfate;
• Bordeaux mixture.

Insecticides are used to control pests:

• "Iskra M2";
• "Confidor Extra";
• "Decis Profi".

Strengthen the root system with the help of growth stimulants:

• "Epin";
• "Heteroauxin";
• "Larixin";
• "Novosil";
• "Kornevin".

Correcting ground imbalance

As soon as it becomes clear which element is missing in the soil, it is necessary to feed it with special additives:

1. Phosphorus. The deficiency is eliminated with the help of “Superphosphate” - 15 g per 10 liters of water, the dosage is designed to treat 1 square meter. m.
2. Magnesium. Foliar treatments are carried out with magnesium nitrate - 5 g per 10 liters of water.
3. Potassium. Use potassium sulfate - 8-10 g per 10 liters of water. Treatment is carried out once every 4-5 days; after 3 procedures, a solution of the drug should be added to the soil - 15 g per 1 square meter. m.
4. Boron deficiency replenished by spraying with a 1% solution of boric acid. The procedure is carried out in the evening.
5. Iron. The bushes are sprayed with a 1% solution of copper sulfate or iron chelate. These products are suitable for foliar treatments.
6. Manganese. The seedlings are sprayed with a 1% solution of potassium permanganate.
7. Molybdenum. Plants should be treated with a solution of ammonium molybdate - 2 g per 10 liters of water.

Traditional methods

You can restore the nitrogen balance with urea - 1 tbsp. l. drug per 10 liters of water. The dosage is calculated for 1 square. m. Foliar treatments are also effective - 1 tsp. for 10 liters of water. During the procedure, the above-ground part of the plant is sprayed.

Organic fertilizers are also used to saturate the soil with nitrogen:

• mullein - 1 liter of fertilizer per 10 liter bucket of water;
• bird droppings - 500 g per 10 liters of water;
• wood ash or soot - 250 g per 10 liters of water.

Important! To increase efficiency, bird droppings can be combined with wood ash.

Agrotechnical techniques

If there is excess moisture, stop watering for several days.To restore balance, add urea to the soil - 1 tsp. solution per 1 sq. m.

To prevent the plants from burning, an additional awning or canopy is installed on the garden bed for several weeks after planting. As soon as the seedlings take root, the cover can be removed.

When planting seedlings, keep a distance to prevent crowding. The distance between plants should be 70 cm.

If the leaves on the tomatoes begin to turn yellow due to lack of light, they cannot be replanted. It is better to thin out the tops by removing leaves that shade each other.

Restoring the root system takes a long time. During this period, it is important to provide the plant with sufficient nutrition and watering.

You can restore the balance of beneficial microelements with the help of additional fertilizing with “nitroammophoska” - 1 tsp. drug per 10 liters of water. Treatment is carried out once every 3-4 days in the evening until the yellowing of the leaves stops.

Preventive measures

Determining the cause of yellowing tomatoes is not easy. It is much easier to follow simple measures that will keep the seedlings healthy:

• observe moderation in watering;
• maintain optimal temperature and humidity levels;
• apply fertilizers in a timely manner;
• monitor the condition of plants in order to recognize diseases in time;
• pest control;
• compensate for the lack of useful microelements;
• do not neglect preventive treatment with fungicides;
• follow the rules of crop rotation;
• regularly disinfect garden tools;
• treat the soil and seed material before planting.

Advice from experienced agronomists

Experienced gardeners know several tricks that allow them to solve the problem of yellowed leaves without cost:

1. You can replenish phosphorus deficiency with fish heads. They are buried in the area next to the tomato beds. With this method, soil saturation occurs slowly and over a long period of time.
2. It is better to tear off yellow leaves rather than leave them on the bushes. Otherwise, plants will waste nutrition on damaged areas.
3. In order not to damage the bushes while tearing off the leaves, they need to be lowered down, pressed against the stem, and then carefully pulled up.
4. To help young seedlings adapt, place them in a sunny place when the first shoots appear. When the air temperature rises to +18°C, the pots with plants can be taken outside for hardening. Seedlings growing on a windowsill must be turned over to the sun once every 7 days.

Conclusion

Yellow spots can appear on tomato leaves for many reasons: care errors, imbalance of beneficial elements in the soil, diseases and pests. To protect the crop, it is enough to follow simple preventive measures.

If the tops on the bushes begin to turn yellow, it is important to correctly identify the source of the problem and eliminate it. Delay and waiting can lead to the death of all plants.