Why Are Tomato Leaves Turning Yellow?

Yellowing tomato leaves are observed on their plots by all gardeners without exception. There is nothing strange here, because yellow leaves in tomatoes appear due to a large complex of different causes. For example, the lack of certain elements in the soil, diseases or pests, too much sunlight or water in the soil (or their deficiency). With the yellowing of tomato leaves there is no need to panic, you should calmly sort out the situation, find the cause of this phenomenon and save the plant in time before it is too late.

Why are tomato leaves turning yellow?
There can be several reasons for the yellowing of tomato leaves. © Jocuri-fotbal

Content:

  • Natural pattern of tomato leaf yellowing
  • Disease and pest activity on tomato leaves
  • Excess or deficiency of water in the soil
  • Deficiency or excessive sunlight
  • Root damage or other root problems
  • Excess or deficiency of essential nutrients

Natural pattern of tomato leaf yellowing

Yellowing of tomato leaves due to natural causes, For example, when transplanting seedlings from individual pots into the ground to a permanent place. In this case, the yellowing of tomato leaves located in the lowest part of the plant is often observed.

This is a quite natural phenomenon, called as adaptation of tomato plants to environmental conditions different from those they had before. Absolutely any tomato transplanting is nothing but a stress for the plants, which usually manifests itself by the yellowing of the leaves and often the very lower ones. Why does this happen?

It is usually a temporary failure in the supply of nutrients from the roots to the vegetative mass. The tomato plant chooses the best option to maintain viability and literally rejects the lower leaves for the benefit of the upper ones.

If you notice that after transplanting a few lower leaves on tomato plants have turned yellow, you should not panic, you should wait a few days, and if the leaves themselves will not fall, then you should remove them manually.

The manifestation of diseases and pest activities

The yellowing of tomato leaves occurs as a result of the effects of certain diseases, such as phytophthorosis, mosaic, fusarium and others, on the plants. Usually yellow tomato leaves indicate the presence of the disease and this is one of the first symptoms. Against most tomato diseases you can use fungicides: Abiga-Pic, Ordan, Thanos, Revus, Consento.

In addition to diseases, pests such as aphids, whitefly, tobacco thrips, Colorado beetle can also cause yellowing of tomato leaves. Against them, you must use insecticides: "Iskra M", "Confidor Extra", "Decis Profi"

Excess or deficit of water in the ground

With a lack of water in the ground, tomatoes begin to save it, trying to reduce the evaporation of moisture, so get rid of leaves by rejecting them. With a lack of moisture, the leaves first curl with a reduction in evaporation, then begin to yellow and die.

Watering tomatoes is necessary, but it is important to monitor the condition of the soil, if there is too much moisture, it will also negatively affect the plants. With too much moisture, tomato plants begin to form an abundant vegetative mass, a lot of leaves and shoots are formed, while the root system can not develop enough and poorly absorb nutrients. To eliminate or stop these negative processes in the plant, you should temporarily stop watering and add nitrogen in the form of urea in the dissolved form, in an amount of 1 teaspoon per 1m2soil.

Why are tomato leaves turning yellow?
If yellowing of the lower leaves after transplanting tomato seedlings - it is normal. © Kevin Lee Jacobs

Deficiency or excessive amount of sunlight

This can also cause yellowing of tomato leaves. So, if plants are planted outdoors in a sparse planting pattern, the plants may suffer from too much sunlight when they are not yet strong enough. In this type of planting, it is advisable to shade the plants from the sun for a couple of weeks after planting if there is a lot of heat.

If the planting pattern is too dense or if the tomato plants are planted in the shade, usually the lower leaves or the leaves in the middle also start to turn yellow. Transplanting such plants is dangerous, it is better to thin out the vegetative mass by removing those leaves that shade each other.

Root damage or other root problems

Often the reason for yellowing leaves on tomato plants is a plant root problem. Most often yellowing leaves on plants with a weak root system, which simply can not provide enough nutrition to the above-ground mass, starvation occurs and the leaves turn yellow. Such plants can be helped by treating them with growth stimulants: "Epin", "Heteroauxin", "Larixin", "Novosil" and the like.

Trouble with the root system of tomatoes occurs for a number of reasons:

  • the roots can be damaged by pests;
  • the roots can be damaged when transplanting seedlings from separate containers into the ground;
  • when loosening the soil too deeply (when fighting weeds);
  • the poor quality of the original seedlings (another cause of weak roots), which can be greasy, elongated, and also grown with considerable economy of space, not allowing the root system to develop fully.

Helping the tomato root system to recover can be difficult, it is better just to wait, providing plants in this period with plenty of nutrition and moisture.

Unsound tomato seedlings usually become sick for a long time after transplanting, and their leaves can yellow not only immediately after transplanting the seedlings, which is quite normal, but also after a long time. Such seedlings are usually well helped by the preparation "Kornevin".

Don't forget that you can restore the balance of the most important elements in the plant by foliar feeding. It is best to use nitroammophoska, which contains all the important elements. Dissolve a teaspoon of it in a bucket of water and work on the plants every 3-4 days in the evening until the new yellow leaves stop showing up. Already yellowed leaves can be removed.

A surplus or deficiency of basic nutrients

Almost the main reason for the appearance of yellow leaves on tomatoes is a deficiency or excess of a number of important elements for plants. To find out what element is missing or too much, it is important to take into account whether the yellowing of the leaves is on the bottom of the plant or on the top, in addition to the fact that the leaves themselves are yellow. Usually it is observed in tomatoes due to nitrogen deficiency.

For details about the signs of deficiency or excess of certain elements in the soil for tomato development, we wrote in the article "What tomatoes lack?"

Nitrogen deficiency

The tomato leaves can either turn yellow or discolored, and young leaves form more small, the plant itself has a weakened appearance. Very dangerous nitrogen deficiency during the active growth of the above-ground mass, as well as during the formation of fruits.

Nitrogen deficiency in the soil must be applied. Most often urea is used for this purpose. The amount of this fertilizer should be equal to a tablespoon per bucket of water, this is the norm per square meter of soil occupied by tomatoes, which are deficient in nitrogen.

You can use cowpea in an amount of a liter per bucket of water, this is also the norm per square meter of soil. It is acceptable to use poultry manure in combination with wood ash or soot. Amount of bird droppings - 500 grams per bucket of water, wood ash or soot - 250 grams per bucket of water, this is the norm per 1m2 plot.

Can also carry out foliar feeding of tomatoes, that is simply their spraying dissolved in water urea. In this case, the concentration should be reduced to a teaspoon per bucket of water. Plants should be treated so that the above-ground part was completely moistened, and then move on to another plant.

These fertilizer concentrations, however, should not be exceeded, because it can cause an excess of this element of nutrition, and this will cause the plant to begin to accumulate excessive vegetative mass, fat, to the detriment of the development of the root system of tomato, which can also lead to the yellowing of the leaves. Fighting an excess of nitrogen is more difficult than with its deficiency: you will have to risk frequently watering the soil to literally wash the nitrogen out of the soil.

Why are tomato leaves turning yellow?
Tomato leaf yellowing can be caused by diseases and pests. © The Hot Pepper

Phosphorus deficiency

Phosphorus deficiency is reflected in tomato plants by yellowing of leaves, their shallowness accompanied by bending edges. Often the stems may also change color to purple or dark green. Leaves usually turn yellow at the bottom of the plant.

To get rid of phosphorus deficiency, fertilize plants with superphosphate at the rate of 15 g per square meter. You can try dissolving superphosphate in warm water in the amount of 10 g per bucket. You should know that superphosphate in water dissolves with a precipitate. Sometimes gardeners bury fish heads in the soil next to tomato plants. This is acceptable, but does not allow the plants to be supplied with phosphorus quickly enough.

Potassium deficiency

Potassium deficiency in tomatoes causes the leaves located at the bottom of the stem to turn yellow and then dry out. Leaves begin to desiccate from the edges, looking like tissue necrosis. The yellowing and desiccation of the leaves is also accompanied by the formation of new leaves, which are usually unnaturally thick and small. The stems become as if they were made of wood. The leaves curl up on themselves before shrinking.

To make up for a potassium deficiency, it is best to first treat the plants with potassium dissolved in water. To do this, use potassium sulfate in an amount of 8-10 g per bucket of water. After 2 to 3 treatments at 4 to 5 day intervals you must apply 15g of potassium sulfate per square meter into the soil, preferably dissolved in water. In addition, zinc deficiency results in brown and grayish blotches on the leaves.

Magnesium deficiency

Magnesium deficiency causes the tomato leaves to turn yellow between the veins and may curl inward, and older leaves become covered with grayish brown spots. Such leaves fall off.

Magnesium deficiency can be corrected by foliar feeding with magnesium nitrate (5 g/10 L).

Calcium deficiency

often it is yellowing of top tomato leaves. In contrast, lower leaves can become unnaturally green when calcium deficiency occurs.

Why are tomato leaves turning yellow?
Tomato leaves also turn yellow from nutrient deficiencies. © LPSP

Boron deficiency

Boron deficiency often causes the uppermost leaves to turn yellow, causing the plant to unnaturally bush and discard flowers. If boron is deficient, the plant should be sprayed with a 1% boric acid solution in the evening.

Sulfur deficiency

Sulfur deficiency initially causes the tomato leaves at the top of the plant to turn yellow, then the lower leaves can turn yellow. This also results in extremely thin and brittle leaves.

Micronutrient deficiencies should be corrected by applying the appropriate fertilizer in the concentrations indicated on the package. For minor micronutrient deficiencies, which can be found out with a full-scale soil analysis of your plot in a laboratory, it is acceptable to apply wood ash, wood soot, or fertilizer representing digested weeds.

Complete. So we have listed the main and most common causes of yellowing leaves in tomatoes. It is possible that our readers have observed leaf yellowing in tomatoes in their plot for other reasons as well. If this has happened, write us about it in the comments.

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