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Time to Read 6 Minutes.
Are you worried about “tomato plant leaves turning brown and curling” or “tomato stem turning brown?” When a tomato plant is under stress, the leaves start changing their natural color. There could be several reasons for brown leaves on tomato plants. Some of the causes may be environmental change, and some of the causes are undue pest infections.
Once the situation gets serious, tomato stalks turn brown. Leaves browning can happen mainly in two different ways. The edge of the tomato leaf turns brown and spreads all over the leaf or either brown spots on tomato leaves.
In this article, I’m going to explain. Why are tomato plant leaves turning brown? What do you do when tomato plant leaves turn brown?
In This Article:
Why are tomato leaves turning brown?
Common reasons for tomato leaves turning brown are russet mite pest infestation, bacterial spot and bacterial speck, tomato blight fungus infection, and over-fertilization. The first thing you should do is carefully examine the plant’s physical appearance and soil. Luckily we can save the plant without reducing yield. Below is a common reason that results in brown leaves on tomato plants.
Tomato Russet Mite Infection.
The Russet mite infected tomato plant turns it into a rusty brown color. This insect is invisible to the naked eye; if you use a 20x hand lens, you can see them on foliage. Some diseases cause the stem to turn brown, but most of the time, it is the tomato rust mite pest infections.
The main symptoms start close to the ground. Lower tomato leaves turn brown, dry out, and spread to the stem and upper leaves. It is essential to control tomato russet mite infection at the initial stage. If uncontrolled, this pest will spread to other plants and eventually destroy all tomato plants in the field.
This insect is active from spring to autumn and cannot survive in low temperatures. These insects are known as rapid breeding pests like tomato leaf miners. They breed quickly in the dry season. Once these mites attacked a single plant they quickly spread to other plants in the garden.
Symptoms of tomato rust mite – Early stages.
- The stems and underneath the leaves turn slightly brown and appear shiny.
- Generally, it is not visible these changes unless you closely monitor them.
- In this stage, if you identify it is a lot easier to get rid of it.
Symptoms of tomato rust mite – Mid-term
- Clearly see the brown part spreads on leaves.
- Browned leaves roll up.
- This condition occurs after about a week without noticing the initial symptoms.
- Now it is almost spread, therefore it is not easy to get rid of tomato rust mite infection.
Symptoms of tomato rust mite – Final stage.
- Discoloration spreads throughout the tomato plant.
- The rolled leaves started to die.
- The damage cannot be stopped, and the strain will eventually die.
How to control Tomato Russet mite infection?
Early identification and prevention are critical for controlling rust mites. Tomato russet mite treatments are horticultural oil, sulfur, and soap spray. All these treatments are organic pesticides that do not affect friendly insects like ladybirds, and bees.
The tomato rust mites pesticide will not be effective if the inspection outbreak. Therefore rapid response is crucial.
Container gardeners can easily prevent further infection by quarantining the infected plant. If you notice brown leaves on tomato plants in containers, first isolate the plant. Then apply the organic pesticide and cover the plant using transparent polythene for a couple of days. Because these pests can easily infect other plants. Plant quarantine will help prevent rust mites outbreaks.
Neem oil treatment.
Neem oil is one of the most effective organic pesticides for tomato russet mite. Unlike leaf miners infection, these pests live underneath the leaves therefore organic pesticides can kill the adult russet mites, and larvae, reducing the fertility of eggs.
Always choose cold-pressed neem oil. It has the Azadirachtin chemical, which is toxic to harmful insects. Neem oil extract does not contain Azadirachtin therefore it is just regular oil that has a more negligible effect on these insects.
Since it is an oil, it does not mix with water. So we need to use an emulsifying agent, and soap is an excellent emulsifying ingredient. I recommend using castile soap liquid for this.
- Add two teaspoons full of neem oil to the cup and half a teaspoon of liquid soap and mix well. Soaps help to mix well. If you can find a small bottle you pour the mixture into a bottle and can shake it well.
- Now mix the solution with 1 gallon (3 liters) of water.
- Spray the neem oil solution to the entire plant including underneath the leaves and stem. Generally, these insects live underneath the leaves.
The best time to spray the neem oil solutions to tomato plants is in the evening when there is no direct sunlight to the plant and the temperature is moderate. There is a risk of tomato leaf burn if you apply it in the bright sun. Once apply neem oil do not water for 24 hours.
Micronized sulfur for tomatoes.
Mined sulfur dust or its spray is another good organic pesticide for controlling russet mites on tomatoes. Sulfur is not water-soluble material, therefore always shop for wettable sulfur powder.
First, dilute the micronized sulfur with water and spray the plant well. Do not apply sulfur solutions after the horticultural oil treatments, it can cause tomato leaves to burn. Moreover, if the temperature is above 90°F, do not use sulfur for tomato plants. It can damage the plant. Moreover, when using sulfur use proper protective measures to protect your eyes and do not use it on windy days.
How to Make Sulfur Spray for Tomato Russet mite.
Use wettable powdery mildew or insecticide sulfur. Check the product instructions first, and if there are any specific instructions, follow them. Use proper protective equipment to prevent inhaling and touching the dust.
- Generally, 4 teaspoons of wettable sulfur powder should be mixed with 1 gallon of water. Mix the solution thoroughly before using it.
- Spray the entire plant, especially underneath the leaves.
Tomato blight is caused by fungi. This fungus infection causes brown tomato leaves. Depending on the fungi infection stage there are two types of blight, and it is Early blight and Late blight.
Early blight: Early blight symptoms start to show after fruiting starts. Initially, small dark brown spots emerge on the bottom tomato leaves. Leaves that have been severely infected become brown and fall off. Infection outbreak in warmer (59°F to 80°F) and humid conditions. Alternaria solani is the fungi that cause this issue.
Late Blight: Late blight symptoms start to show at any stage of the tomato plant’s growth. In a cool climate infection rapidly spreads to other plants. Initially, large dark brown spots appear on leaves and fruits. In high humidity, White mildew appears on infected leaves. Inspection gets serious in cool climates (60°F to 70°F). Phytophthora infestans are the fungi causing this issue.
Tomato blight treatment.
Since tomato blight is a fungus, you can use any available fungicide. There are several organic treatments for tomato blight. Baking soda is a good organic treatment for tomato blight infection.
How to make baking soda treatment for tomato blight.
- Take 1 teaspoon of baking soda, a teaspoon of vegetable oil, and ½ teaspoon of liquid soap.
- Mix everything with a cup of water. Once it is mixed, dilute the concentration with 1 gallon of water.
- Baking soda changes the leaves’ surface pH level, vegetable oil helps to stick the solution leaves and liquid soap helps the emulsifying oil.
- Apply the solution to every part of the tomato plant including underneath the leaves. Do not apply the solution in direct sun, which will cause leaf burn.
Applying an excessive amount of chemical fertilizer can cause tomato leaves turning brown. This overuse can happen more frequently used than the manufacturer’s instruction or using a high dose. When applying a high amount of fertilizer, increase the soil salt level, and excessive fertilizer usage will result in the tomato leaves edge turning brown.
Sometimes tomato overfertilization can kill the plant. If you use organic compost, there is no risk of brown leaves on tomatoes.
How to fix overfertilized tomato plants?
Overfertliezed plants can save using washing the excessive salt on the soil. You have to water the tomato plant thoroughly, and this method is most effective for garden beds and containers growing tomatoes.
Alternatively, you can change the potting soil, but you should do so so that the replanting of a tomato plant does not cause shock. If the plants are small and do not develop fruits, you can replant them, without stressing the plant.
Should I remove brown leaves from tomato plants?
It is totally good practice to remove pests, fungus, and bacteria-infected brown tomato leaves from the plant and burn them. Do not use it for compost piles or mulch. Removing discolored leaves will reduce further infections. When you destroy infected leaves it controls the pests, fungi, and bacterial population.
However removing brown tomato leaves will not help to control pests, fungi, and bacteria infections. You have to use proper treatments.
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