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Time to Read 7 Minutes.
Tomato plants thrive well in perfect soil, with correct watering and the right amount of light. These plants require good attention; if the environmental conditions are not favorable, the plant gets stressed. Tomato leaves turning yellow and brown are common problems that many home gardeners face.
There are several reasons for yellow leaves on tomato plants, and it can be either pest infection, overfeeding or underfeeding, environmental changes, or fungal infection.
This article will discuss possible reasons for tomato leaves turning yellow and brown. How to fix yellow leaves on tomato plants.
In This Article:
Reasons for Tomato Leaves Turning Yellow And Brown.
In this article, I’ll discuss 10 reasons that tomato leaves are turning yellow. With close inspection, you can find the exact reason.
Overwatered tomato plants’ symptoms are yellow leaves and stems. We can quickly recover tomato plants from overwatering. Overwatering can happen mainly in two ways. Frequent watering tomato plants or waterlogging tomato potting soil.
Symptoms of the overwatered tomato plant.
Initially, you can see the bottom tomato leaves turning yellow, and later it spreads to tomato roots rotting. Finally, an overwatered tomato plant can kill.
Water only dries up the soil. Make sure that topsoil is dry before water. Between two watering tomato soil should not completely dry, it can cause tomato splitting.
Make sure that your tomato potting soil is well-drained and well aerated. Compact soil retains more water, and it will easily cause overwatering. When you are planting tomato seedlings in the ground, avoid clay soil.
Nitrogen is required for the growth of healthy, green leaves and for the process of photosynthesis to occur. Photosynthesis is dependent on the development of Chlorophyll pigment in plants, and nitrogen is required to develop that pigment. Thus there is a slowing down of plants that have been depleted of nitrogen.
Generally, potted tomato plants can suffer nitrogen deficiency due to overwatering. Too much watering of tomato plants flows out the nutrients from the drainage hole, and this is a mobile nutrient deficiency.
Nitrogen deficiency symptoms.
Nitrogen deficiency is another reason for tomato leaves turning yellow. Nitrogen deficiency can see old tomato leaves. Initially, older tomato leaves turn yellow, and younger leaves remain green. Nitrogen deficiency causes tomato leaves chlorosis of the entire leaf, including veins. It typically starts from the tomato leaves’ tip and spreads to the leaf petiole.
Later, the yellowing of the tomato leaves spread throughout the tomato plant, including the new leaves. Finally, the entire tomato plant turning light yellow color. Another common symptom is stunted growth, and you can see smaller tomato plants.
Apply high nitrogen liquid fertilizer. Liquid fertilizer is more quickly absorbable to tomato plants than granular fertilizer, for organic growers use cattle manure. It is rich in nitrogen.
Potassium is another essential nutrient required for the growth of tomato plants. This nutrient is critical for tomato plants’ cell divisions and root development. Furthermore, it increases the plant’s ability to withstand infection. Lack of potassium of tomato plants leaves turning yellow. Potassium is a mobile nutrient. So initial symptoms show older growth of the plant.
Potassium deficiency symptoms.
The border of the old tomato leaves turns yellow, and the middle part of the leaves is still green. Here you can see dead or brown spots on tomato leaves. If there is no more potassium, then the discoloration of the tomato leaves spreads to the young leaves.
Apply high potassium (K) liquid fertilizer to quickly increase the potassium level in the tomato potting mix. Tomato is a relatively less six months lifecycle crop, so you have to use quick-release fertilizers.
Banana peel water and powder are excellent potassium-rich organic fertilizers for organic tomato growers.
Magnesium is a micronutrient that tomato plants require, and it is a mobile nutrient. And you can see the nutrient deficiency in lower leaves first and later spread to younger leaves.
This micronutrient also grows chlorophyll, which is essential for the photosynthesis of tomato plants. Chlorophyll deficiency is also known as Interveinal Chlorosis (micronutrient deficiency). This macronutrient deficiency severely affects plant growth, and the discolored parts do not turn green after treatment.
Magnesium deficiency symptoms.
Lower tomato leaves turn yellow, and vines keep the green color. It is similar to nitrogen deficiency, though, with time, yellow parts turn to white. Later the new leaf size is reduced. It is a magnesium deficiency if you notice yellowing from the leaf’s petiole.
Apply cal-mag liquid fertilizer or magnesium sulfate fertilizer. Thoroughly apply the solution to tomato foliage because this nutrient deficiency can quickly fix by foliage feeding. Moreover, the application of Epsom salts (magnesium sulfate) is another solution to supply magnesium to tomato plants.
Do not mix Cal-Mag and Epsom salts together or with any other fertilizer. Epsom salt can be applied as a side coat or as water-soluble fertilizer. Mix 1 or 2 teaspoons per 1 gallon of water. If you use Epsom salt as a dessert, apply a tablespoon to each tomato plant.
A lack of iron nutrients in the soil cause tomato leaves to turn yellow. Iron is a micronutrient that helps develop tomato leaves’ green color, responsible for chlorophyll green pigment. Iron deficiency can be seen in younger tomato leaves, and this is an immobile nutrient deficiency. That is why we can see younger tomato leaves turn yellow. This nutrient deficiency is called chlorosis.
An iron deficiency causes high soil pH. If your tomato plants suffer iron deficiency every year, it is better to lower the potting soil pH level.
Iron deficiency symptoms.
The typical symptom is younger tomato leaves turning yellow and vines remaining dark green. Tomato iron deficiency symptoms show leaves tips starting yellowing. Manganese and iron deficiency symptoms are similar; the only difference is iron deficiency symptoms show leaves edge/tips.
The iron nutrient requirements can be easily supplemented by foliage feeding. Applying ferrous sulfate solutions directly to foliage is the quickest way to supply iron to tomato plants: Mix 1 or 2 oz of ferrous sulfate powder in 1 gallon of water.
Another solution is to apply Chelated Liquid Iron fertilizer. You can find different brands of Chelated Iron fertilizers online or at your local fertilizer shop.
UV filtered water also causes iron deficiency. Therefore, always avoid such water. We usually see this problem in hydroponic tomato plants.
Manganese is another micronutrient required for tomato plants, and this nutrient is considered immobile. Iron and manganese deficiencies show similar symptoms, but we can quickly identify the exact nutrient deficiency on closer inspection.
Manganese deficiency symptoms.
Younger tomato leaves turn yellow from the leaf petiole, and veins keep the remaining green color. In Manganese deficiency, leaves discoloration start close to the leaf petiole.
Apply manganese sulfate water-soluble fertilizer.
Downy mildew infection.
Mildew is a fungal disease that causes tomato yellow leaves. This fungal affects new leaf growth. This Plasmopara viticola pathogen attacks greenish parts of the tomato plant, including leaves and vine. Severe infection of this fungus directly reduces the yield, causes inflorescence, and shoots rot.
Tomato downy mildew Symptoms.
Initial downy mildew infected symptoms are small yellow spots on tomato leaves, and later the entire leaves turn yellowish. When it comes to the spread of downy mildew on tomatoes, it is caused by both wind and high relative humidity.
Treatment for tomato downy mildew.
Apply fungicide to the entire plant and topsoil. Organic tomato growers can use neem oil. Apply two or three teaspoons of oil with half a teaspoon of liquid soap and mix the solution well. Then mix the neem oil solution with 1 gallon of water and spray the entire plant and topsoil.
Early blight is another typical tomato fungal disease that infects tomato plants in the early growing stages. Once the leaves are infected tomato leaves turning yellow. These fungi live in soil, spreading via contaminated soil and water. This fungal disease is caused by two similar species called Alternaria tomatophila and Alternaria solani.
This pathogen spreads in warmer environments (82 to 86 F) with over 90% relative humidity. Tomato seed and tomato transplants can also be infected with the pathogen.
Tomato Early blight symptoms.
The initial symptoms of tomato blight show older leaves close to the ground.
Apply good copper-based fungicide thoroughly. Especially spray the solution to the bottom leaves and soil.
Further infection can control by mulch to the soil around the plants. This could be anything from fabric to straw to plastic mulch.
Furthermore, we can use physical control to prevent disease infection by watering the base of each plant, pruning the bottom leaves, and so on. Pinch off any leaves with leaf spots and keep the leaves dry to prevent the disease from spreading.
Transplant shock can cause tomato leaves turning yellow at the bottom and drop their leaves. Before the transplant, you have to harden tomato seedlings. If you notice a young tomato plant’s leaves yellowing, transplant shock can be.
Tomato whiteflies are another reason for yellow leaves on tomato plants. These insects suck the leaves’ sap. A serious infection causes leaves to yellow. There are several organic treatments for tomato whiteflies.
How to control whiteflies on tomato leaves.
- Mix three teaspoons of cooking oil (vegetable, sunflower, coconut, etc oil.) or neem oil with liquid soap.
- Mix the oil thoroughly with the liquid soap until it changes its color.
- Then dilute the white oil with a gallon of water and spray the affected leaves. These pests live under leaves. So spray every leaf.
You have to re-apply this white oil every 4 to 7 days until get rid of whiteflies. The best time to apply white oil for whiteflies is evening. Do not apply in direct sun, it can cause leave a burn.
The yellowing of leaves of tomato plants can also occur as a natural part of the aging process of plants, and this happens after the plant has finished producing fruit for the season. Here we can mainly identify two types of tomatoes, namely, Determinate and Indeterminate.
Determinate tomato seedlings die once after tomato production. Indeterminate produce fruit throughout the growing season.
Should I Remove Yellow Tomato Leaves From Tomato Plant?
The yellow tomato leaves do not need to be removed. The primary cause of tomato leaf yellowing is a deficiency in one or more essential nutrients. As a result, nearby leaves are not infected. Tomato leaves that have become yellowed due to a fungus need cut off and thrown away. To avoid additional infection, you should use a fungicide. Therefore Depending on the situation, you should remove yellow leaves from the tomato plants.
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