Tomatoes are the most popular plant grown in home vegetable gardens. Growing a good crop of tomatoes starts with a few key practices:
Read our guide to growing tomatoes in a home garden for more details. In Maryland, tomato plants are susceptible to several diseases, pests, and, at times, unfavorable weather conditions that can disrupt their growth, productivity, and/or eating quality. Use this picture guide (or the table below it) to identify the most common problems of tomatoes. Follow the links to learn how to manage these problems using integrated pest management and other best practices.
As an avid tomato gardener, I occasionally notice brown stems on my plants which can be alarming at first glance. However, through experience I’ve learned that brown stems are quite common and usually easy to remedy if caught early. In this article I’ll provide a comprehensive guide to identifying, managing, and preventing brown stems on tomato plants.
What Causes Brown Stems on Tomatoes?
There are several potential causes of brown tomato stems:
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Environmental stresses – Extreme temperatures drought, flooding or rapid growth spurts can all damage stems. This usually appears as scarring or bruising on the stems.
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Pest damage – Hornworms cutworms or flea beetles may chew on stems leaving holes, scars, or openings for disease. Inspect carefully for signs of insects.
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Diseases – Fungal issues like blights, wilts, stem rots, and cankers can all discolor stems from brown to black. Diseases may start at the base or roots and spread upwards.
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Weedkillers – Herbicide drift or contamination can distort growth and cause strange stem malformations on contact. Avoid glyphosate near tomatoes.
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Physical injury – Accidental cracks, pruning cuts, hail damage, or transplant shock can harm stems. Monitor for infection.
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Older stem aging – Lower portions of the stem naturally turn woody and brown as the plant matures. This is normal for older foliage.
Identifying the Cause of Brown Stems
Carefully inspect plants to pinpoint what factors led to the stem problems. Signs to look for include:
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Black or brown lesions spreading from the base – likely a soil-borne disease
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Upper stem discoloration – indicates blight or environmental damage
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Wilting leaves – can signal wilt diseases or under-watering
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Chewed areas or holes – caused by hornworms or other pests
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Weird malformations – potentially from herbicide contact
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Scattered scars – may be physical injury or aging lower stems
Dealing With Diseased Brown Stems
If fungal or bacterial diseases are the culprit, prompt action is required:
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Remove and destroy affected plants immediately to prevent spreading. Don’t compost them.
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Disinfect any gardening tools and equipment that came in contact using a 10% bleach solution.
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Apply preventative fungicides on remaining plants as needed. Look for copper-based or Bacillus subtilis products.
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Improve airflow and reduce moisture on plants through proper spacing, mulching, and drip irrigation.
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Solarize soil using clear plastic sheets to kill pathogens in plant beds before replanting tomatoes.
Managing Environmental Stresses
For brown stems caused by stresses like weather, make these adjustments:
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Add mulch and use drip irrigation to maintain even soil moisture in periods of heat or drought.
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Provide shelter, row covers, or greenhouse structures if cold snaps, hail, or heavy rains are impacting plants.
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Stake or cage plants to support growth and prevent damage from drooping, wind, or touching soil.
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Ensure consistent watering in morning hours without oversaturation of soil. Check moisture levels regularly.
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Test soil and amend appropriately with fertilizer to prevent nutrient deficiencies.
Controlling Pest Damage
To protect against chewing insects:
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Manually pick off hornworms, flea beetles, caterpillars when found on plants.
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Use Bacillus thuringiensis (Bt) spray for organic caterpillar and worm control.
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Apply lightweight row covers as a physical barrier against pests.
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Eliminate weeds around plants that can harbor insect populations.
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Rotate tomato planting locations annually to disrupt pest life cycles.
Preventing Future Brown Stem Issues
Here are some key tips to avoid brown stems going forward:
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Select disease-resistant, robust tomato varieties when possible. Look for “VF” labeling.
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Prune plants to improve airflow and remove any diseased, dead foliage.
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Check seedlings for damping-off fungus and avoid overwatering.
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Till under plant debris thoroughly after harvest to speed decomposition.
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Use preventative copper fungicide spray after rain or periods of high humidity.
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Monitor soil fertility and use crop rotation when growing in beds.
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Inspect regularly for early signs of pests or disease infection.
When to Worry About Brown Stems
As long as brown areas remain small and isolated, the tomato plant will likely recover on its own. But if discoloration is spreading quickly or accompanied by major wilting, it’s best to remove and destroy affected plants immediately to protect the remaining crop. Stay vigilant for signs of deterioration.
Noticing brown stems on tomato plants is very common, but doesn’t have to lead to catastrophe with timely care. Focus on identifying the trigger, whether environmental, disease, or pest related. Then apply the appropriate organic solutions to get your tomato crop back on track. With preventative practices and early interventions, brown stems can be successfully managed for a plentiful tomato harvest.
Anthracnose Advanced symptoms of anthracnose on tomato fruit. Photo: J. Traunfeld, UME
- Symptoms: circular sunken spots with darkened centers, usually on overripe fruits.
- Anthracnose disease is caused by more than a dozen species of fungus in the genus Colletotrichum.
- The fungi overwinter in seeds, soil, and plant residues.
- Pick fruits before they ripen fully.
Tobacco or tomato hornworm A tobacco hornworm larva (Manduca sexta) chews a leaf. Photo: Eddie McGriff, University of Georgia, Bugwood.org
- Symptoms: leaves are chewed or stripped off of branches.
- This chewing is caused by the caterpillars of the hornworm moth.
- They are a mid to late-summer pest. Remove caterpillars by hand and discard.
- A large percentage is controlled by a wasp parasitoid (natural enemy)
Brown Spots on Tomato Leaves? Leaves Turning Yellow? It Might be This!
FAQ
Why are the stems of my tomatoes turning brown?
Tomatoes produce roots from their stem very easily, and this is usually no cause for concern. Dead, rotten patches on the stems: A disease called Didymella stem rot (caused by the fungus Didymella lycopersici) can attack the stems of tomatoes causing brown, rotted patches, at any height but most often at the stem base.
Can tomato plants recover from stem rot?
You cannot reverse stem rot, but it may not progress if you remove the mulch as we suggest. There are not “products” that can cure this, its a matter of environment.
What does an overwatered tomato plant look like?
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Wilting or Drooping Leaves:Overwatered plants will have leaves that droop or wilt, which is different from the crisp, dry leaves of an underwatered plant.
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Yellowing Leaves:Yellowing leaves, especially on the lower leaves, can indicate overwatering.
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Blisters or Bumps on Leaves:Raised blisters or bumps on the leaves are another sign of overwatering.
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Wet Soil:The soil will feel soggy and may even hold standing water, indicating that the plant is getting too much water.
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Foul Odor:The soil may have a foul or musty odor, which is a sign of fungal growth and root rot.
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Brown or Mushy Roots:Healthy roots are white and firm. Overwatered plants will have brown or black, limp, and mushy roots.
Why are the branches on my tomato plants dying?
Possible causes include lack of water, fungal wilt diseases, tomato spotted wilt virus, walnut toxicity and stalk borers. Lack of Water. Tomato plants require approximately 1 inch of water per week. Plants may wilt badly when soils are dry, but will revive rapidly when they are watered.
Why do tomatoes turn brown?
Most gardeners spend long hours deciding what to grow and how to provide the best growing conditions for their plants to thrive. An abundance of healthy, big fruit is the goal at the end of the day! Tomato plant stems turn brown because of diseases caused by stem rot, blight, wilt, and bacterial canker.
What are the brown specks on my tomato plant?
If you notice strange brown specks across your tomato plant leaves, you’ve got a spider mite problem. Also known as two-spotted mites, these pests love to infect tomato plants in large groups, nestling on the undersides of leaves.
How can you tell if a tomato plant has a problem?
When checking our tomato plants for potential problems, we often overlook the stem. Tomato stem problems tend to go unnoticed until they are completely out of hand. Normally, problems are identified by the look of the plant – wilting branches or yellowing leaves.
What causes black spots on tomato stems?
The most common causes of black spots on tomato stems are early or late blight. Early blight, caused by the fungus Alternaria solani, is identified by dark brown or black spots on all parts of the plant, including the stem. These spots typically appear on the stem just above the soil line.
What are the small white or brown bumps on tomato stems?
Tomato stems often develop small white or brown bumps. These small growths are actually roots. Or, to be exact, the first stage of a root. They may look dangerous, but they are completely normal and are usually no cause for alarm.
Where do early blight spots usually appear on tomato plants?
Early blight, caused by the fungus Alternaria solani, is identified by dark brown or black spots on all parts of the plant, including the stem. The spots normally appear on the stem just above the soil line.