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Tomato plant leaves turning brown can be caused by several things. Sometimes, it might be natural, and other times, it might be caused by bacteria or diseases.
The most important thing is to identify the signs quickly and apply solutions to save your plants from dying. Here are 17 reasons why your tomato plant leaves are turning brown
1. Canker
Some bacterial diseases, such as canker, can cause tomato leaves to turn brown. Cranker is caused by an organism infesting tomato seeds. Symptoms can include wilting, browning, and yellowing around the borders.
Unfortunately, canker is not treatable, so treating your tomato seeds before planting is best to prevent its growth.
2. Septoria Leaf Spot
Septoria leaf spot is a fungus that affects tomato leaves. It is prominent in wet and humid areas. It appears as a round gray spot around the bottom of the leaves, eventually causing browning. Septoria leaf spot treatment includes removing the affected leaves, using antifungal sprays, or controlling weeds in your garden.
3. Spider mites
Spider mites are tomato pests that arise from too many nutrients, underwatering, or too much nitrogen. Symptoms of spider mites are yellowing or browning of leaves around the top area, curling of leaves, and spots underneath the tomato leaves. Use
4. Underwatering
The most obvious sign that your tomato plants are not getting enough water is when the leaves turn brown. Drooping and wilting of leaves may occur at later stages, and the dehydrated leaves become crispy.
Fortunately, watering your plants consistently fixes the problem. The best time to water your tomato plant is in the morning. Water at the soil level to keep the leaves dry, and only water your plant if the top three inches of the soil feel dry to prevent overwatering.
5. Early Blight
Early blight is one of the most common reasons your leaves turn brown. Early blight is caused by the fungus Alternaria Linariae. In the beginning stage, early blight targets older leaves and causes them to have brown, round spots. Eventually, these leaves dry up and may cling to the stem.
To solve this problem, you will have to prune the affected tomato leaves carefully. Also, apply a synthetic fungicide.
6. Late Blight
Late blight is caused by the pathogen Phytophthora infestans. The symptoms include brown patches surrounded by gray borders on the leaves.
Late blight is trickier to manage than early blight. However, solutions include digging up and properly disposing of the affected plants. Remember not to plant in the same place where the affected plant was uprooted. Also, avoid leaving water on your plant’s leaves for too long.
7. Verticillium Wilt
Verticillium wilt is a fungal disease that affects the soil and makes it hard for the plant to absorb the nutrients needed for growth. Although it doesn’t kill the tomato plant, it can stunt its growth.
The early signs include wilting, yellowing of the bottom leaves, and stunted growth. The late signs are the browning of leaves. Since it is a soil-borne disease, there’s no solution. Once a plant has been affected, it’s best to remove it and not compost it.
8. Nutritional Deficiencies
Another reason why tomato plants may turn brown is nutritional deficiencies. Lack of magnesium can cause the leaves to turn yellow and then brown. To solve this problem, ensure you give the plant the essential nutrients like nitrogen, phosphorus, and potassium, which are important for the plant to thrive.
9. Bacterial Disease
Some bacterial diseases, such as Xanthomonas, affect the leaves of tomatoes. The most obvious sign of bacterial disease is brown water spots on the leaves. If not treated urgently, the disease can spread to the tomato itself.
You can prevent bacterial diseases by planting tomato varieties that are immune and buying clean seeds.
10. Root Damage
When a tomato plant’s roots are damaged, from transplant shock, pests, or physical injury, they struggle to absorb water and nutrients. This stress can cause the leaves to turn brown and wilt. To prevent this, handle the plant gently when transplanting and ensure the soil is loose enough for root growth.
11. Herbicide Exposure
If used incorrectly, herbicides can curl the leaves and turn them yellow and brown. Once you notice signs of herbicide exposure, wash the plant’s leaves immediately and thoroughly. You might also need to prune affected leaves.
12. Sunscald
Too much exposure to sunlight and excessive pruning cause sunscald. Symptoms may include yellowing or browning of the upper side of the leaf. Unfortunately, once the leaves and fruit have been affected, the only solution is to remove them. Ensure you shade or cover the plant with a cloth to avoid too much exposure to the sun.
13. Poor Drainage
Poor soil drainage is another reason your leaves are turning brown. When soil becomes clogged with water, it can lead to other problems, like fungal disease. You can improve soil drainage by applying compost.
13. Salt Build-Up
Excess salts in the soil from fertilizers or hard water can dehydrate tomato roots, leading to browning leaf edges. To prevent salt build-up, flush the soil periodically with fresh water and avoid over-fertilizing.
14. High Temperature Stress
Tomatoes grow well in warm temperatures, usually between 71 and 84 degrees. At higher temperatures, they begin to show signs of stress, including browning of the leaves. Ensure you shade your plant when it starts showing signs of excessive heat.
15. Cold Weather
On the other hand, cold weather can also cause tomato leaves to turn brown. In fact, any sudden change in temperature causes stress for your plant. Avoid planting tomatoes in freezing temperatures to prevent brown leaves. Mulching your soil aids in heat retention and can promote healthy leaves. Also, use protective materials to cover your plants during cold weather.
17. Unhygienic Environment
The environment may not be an obvious reason your leaves turn brown. But if you’ve done everything and nothing seems to work, it’s best to check the environment where your tomato is planted. Ensure you’re weeding the area and keeping it dirt-free.
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Sandra Enuma
Sandra Enuma is a writer who's as comfortable with a trowel as she is with a keyboard. She’s passionate about sharing simple, down-to-earth tips to help you start and manage your own home garden, no matter your experience.
