Some common tomato diseases are starting to show up on Minnesota tomatoes, even though a lot of the state is dry. Notice that the older leaves are turning yellow and getting spots? Read on to learn more about two common fungal diseases that affect Minnesota tomatoes.
As a tomato gardener, few things are more frustrating than seeing the leaves on your prized plants turn brown. After putting in all that care and effort to nurture your tomatoes, those browning leaves seem to signal trouble. But don’t despair! Brown leaves on tomato plants don’t necessarily spell doom for your crop By understanding the common causes and solutions for this issue, you can get your plants back to health
What Causes Brown Leaves on Tomato Plants?
There are several possible causes for tomato leaves turning brown:
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Underwatering – Tomato plants need consistent moisture, so insufficient watering can cause browning leaves, especially around the edges
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Overwatering – Too much water prevents roots from getting oxygen, causing root rot that damages leaves.
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Hot, dry weather – Plants stressed by heat and drought will wilt and brown. Mulch and shade cloth can help.
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Diseases – Fungal and bacterial diseases like early blight, Septoria leaf spot, verticillium wilt, and late blight can lead to brown spots.
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Pests – Spider mites, whiteflies, hornworms, and other pests that suck juices from leaves can cause browning. Look for webs and tiny insects.
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Sunscald – Direct sun hitting leaves can dry out and brown them. Ensure plants have adequate shade during peak sunlight hours.
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Poor nutrition – Lack of nitrogen, phosphorus, or other nutrients due to poor soil can cause lower leaves to yellow and brown.
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Herbicide damage – Drift from weed-killers can make tomato plant leaves turn brown around the edges or in spots, as can concentrated fertilizer touching leaves.
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Transplant shock – Newly transplanted seedlings may show temporary browning leaves as they establish roots and adjust.
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Old leaves – Lower leaves naturally turn brown and drop as the plant ages. This is normal, especially for mature plants setting fruit. Prune old growth.
What to Do for Brown Leaves on Tomato Plants
If your tomato leaves are browning, take these steps to get your plants healthy again:
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Identify the cause – Look for patterns on leaves, web or insects, or issues with soil, watering, or care to diagnose the problem.
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Improve growing conditions – Tomato plants thrive with 8+ hours of sun, consistently moist but not soggy soil, temperatures between 70-85°F, and shelter from wind. Optimize these.
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Treat pests – Use insecticidal soap, neem oil, row covers, or other organic methods to control pests without harming beneficials.
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Prevent disease – Space plants for airflow, stake stems, water at base, remove lower leaves, use disease-resistant varieties.
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Fix nutritional issues – Test soil and amend with compost and organic tomato fertilizer as needed. Foliar feed plants showing deficiency.
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Remedy underwatering – Water tomatoes 1-2 inches per week, aiming for consistent moisture in the top 6 inches of soil.
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Allow soil to dry between waterings – If overwatering, allow the top 2 inches of soil to dry before watering again.
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Filter sunlight – On hot days, shade plants during peak sun hours using shade cloth, shade structures, or large companion plants.
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Prune damaged leaves – Remove badly infected or dried leaves to prevent disease spread. Dispose of debris promptly.
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Evaluate transplant issues – Give recent transplants a week or two to recover from shock before taking further action.
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Monitor for improvement – After taking corrective steps, allow 1-2 weeks for the plant’s health to rebound before doing anything drastic.
When to Worry About Brown Tomato Leaves
As long as you catch brown leaves early and address the underlying cause, there’s a good chance you can revive affected tomato plants. However, take note of these red flags:
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Leaves brown and wilt rapidly – This can signal verticillium wilt, bacterial wilt, or late blight – aggressive diseases requiring plant removal.
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Lower leaves brown first – Potential signs of early blight or Septoria leaf spot, which start on older leaves. Treat quickly.
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Browning spreads upward – Symptom of early blight, Septoria leaf spot, verticillium wilt and other lethal diseases. May be time to replace plant.
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Webbing or tiny pests on undersides of leaves – Severe spider mite infestations can kill plants. Apply insecticidal soap immediately.
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Brown spots with yellow halos appear – Distinct symptom of early blight and Septoria leaf spot. Prompt treatment is key.
Don’t give up too quickly on browning tomato plants – but also know when it’s time to replace severely diseased specimens so they don’t infect the rest of your crop.
Enjoy a Bountiful Tomato Harvest with Healthy Plants
When you see tomato plant leaves turning brown, it pays to investigate the cause and take appropriate corrective action. Catching issues early and optimizing growing conditions gives your plants their best shot at outgrowing minor problems. Then you can look forward to a prolific tomato yield!
Two fungal diseases with similar life cycles Early blight causes larger, amorphous brown spots with concentric rings
As tomatoes start to set fruit, gardeners often notice brown spots on the lower leaves. This can be caused by one of two fungal diseases: early blight or septoria leaf spot. Both of these diseases like damp places and splashing water, so they can spread whenever there is water on the leaves.
Early blight is the one most commonly seen tomato disease across Minnesota. The disease spores survive in crop debris and weeds, then infect this years plants via splashing water. Early blight first infects the oldest leaves, with infected areas turning brown and developing concentric rings. Brown spots, also with concentric rings, can also be seen on stems. As time passes and leaves are wet, the disease can spread upward. Infected fruit develop leathery, dark spots and fall off the plant.
Septoria leaf spot has similar biology to early blight. The disease survives in the field on solanaceous weeds and infected plant material. As fruit starts to set, septoria is able to infect the oldest leaves. Septoria leaves a leaf with many small dark spots that can turn tan in the middle as they get bigger. As time passes, the disease will move up the plant, though fruit infection is rare.
How To Turn Yellow Leaves On Tomato Plants Green (5 Hacks)
FAQ
How do you fix brown leaves on tomato plants?
Why are the leaves on my tomato plant curling and brown?
What do overwatered tomato leaves look like?
Should I cut off brown tomato leaves?
Why are my tomato leaves turning brown?
Various mites, including spider mites and russet mites, can cause tomato leaves to turn brown. They are most common on the lower leaves of plants, though if the infestation grows large enough, the whole plant can be impacted. Mites feed on the nutrients in the cells of your tomato plant’s leaves.
Why do tomato leaves turn black?
It causes the leaves to develop large, dark brown spots that eventually turn black. Aphids: These small insects suck sap from tomato plants, which can cause the leaves to turn brown. Spider mites: These tiny mites feed on the sap of tomato plants, which can also cause the leaves to turn brown.
How do you prevent Brown tomato leaves?
Here are some tips for preventing brown tomato leaves: Inspect your plants regularly for pests and diseases. If you see any pests or signs of disease, treat them immediately. Water your plants regularly, but don’t overwater them. Tomato plants need about 1 inch of water per week. Fertilize your plants regularly with a balanced fertilizer.
How do you know if a tomato plant has late blight?
Leaves develop brown patches that turn dry and papery when tomato plants become infected with late blight. Sometimes a white mold grows along the edges of the brown patches. If your tomato plants have late blight you will also notice blackened areas along the stems and the tomatoes develop hard brown lesions. Late blight on a tomato plant.