As an avid tomato gardener, I sometimes see brown stems on my plants, which at first glance can be scary. But I’ve learned that brown stems are pretty common and are usually easy to fix if you catch them early. This article will tell you everything you need to know to find, treat, and stop 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: High or low temperatures, drought, flooding, or sudden growth spurts can all hurt stems. This usually appears as scarring or bruising on the stems.
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Pest damage: Cutworms, hornworms, and flea beetles can chew on stems, leaving holes, scars, or gaps that diseases can enter. Inspect carefully for signs of insects.
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Fungal diseases like blights, wilts, stem rots, and cankers can turn stems from brown to black. Diseases can begin at the roots and spread to the leaves.
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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: round, sunken spots with dark centers, usually on fruits that are too ripe.
- This disease is caused by more than a dozen different types 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.
- These holes are made by the caterpillars of the hornworm moth.
- They are a mid to late-summer pest. Remove caterpillars by hand and discard.
- A large portion is managed by a wasp parasitoid, which is a 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. At the end of the day, you want lots of big, healthy fruit! Dead stems on tomato plants are 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. These pests, which are also called two-spotted mites, love to grow in groups on tomato plants and hide 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.