Tomato Leaves Turning Black? Here’s Why and How to Fix It

How to Bring Black Tomato Leaves Back to Life

Are you seeing black spots appearing on the leaves of your tomato plant? Worried that your plant is slowly dying on your watch?

We’ve got good news for you! With the right diagnosis and treatment, you can bring your tomato plant back to life. 

Read on to find out the different causes of why tomato leaves turn black and how to treat them. 

Why do tomato leaves turn black?

tomato leaves turn black
Image: The Green Pinky

Tomato leaves usually turn black because of bacterial and fungal plant diseases. They may be soil-borne or airborne, infecting the leaf tissues and causing harm and even death to the tomato plant. 

Here are the 12 most common diseases that cause tomato leaves to turn black:

1. Early Blight

Early Blight
Image: University of Maryland
Cause/s• Alternaria tomatophila
• Alternaria solani 
Symptom/sBlack lesions with concentric circles
Part/s affected• Leaves
• Stem
• Fruit
Treatment / PreventionRemove the tomato plant

You’ll know your tomato plant is infected by early blight when you see dark lesions in concentric circles, like a bullseye, on its leaves. 

It’s caused by the soilborne fungi Alternaria tomatophila and Alternaria solani. They thrive in warm temperatures (75°F or 24°C and above) and high humidity. 

The infection first appears on the lower leaves of the tomato plants. It later moves upward, damaging the stem with sunken and dry brown spots. 

Early blight also affects tomato fruit, where its skin will show sunken black spots with concentric circles.

If you have potatoes, you’d also want to move them away from the tomato plant because they can also be infected by early blight. 

How To Fix

Remove the infected tomato plant.

Uproot the whole tomato plant. The fungi can survive over winter in these plant debris, so getting rid of them will prevent future early blight infections.

2. Late Blight

 Late Blight
Image: Michigan State University
Cause/sPhytophthora infestans
Symptom/s• Black spots on edges of lower leaves
• White mildew dots above dark spots
Part/s affected• Leaves
• Stem
• Fruit
Treatment / PreventionApply fungicide regularly

Late blight is one of the most common tomato plant diseases that cause headaches to gardeners. When you see black spots on the edges of your tomato leaves, your plant is most likely sick of late blight. 

The fungi Phytophthora infestans thrive in cool weather and moist areas, usually on the wet lower leaves of the plant. 

It spreads rapidly and can wipe out an entire field of crops in a short time. In fact, late blight is the culprit for the Irish potato famine of 1840. 

This disease does not only affect the leaves but also spreads through dark patches in the tomato plant’s stem. The tomato fruit also gets dark and firm lesions on its surface. 

Unfortunately, it’s a sure sign of death once your tomato plant is infected by late blight, so removing the infected plant is the only way to solve the problem. 

How To Fix

Apply fungicide regularly.

The best way to deal with late blight is prevention. Fungicides make the plant’s leaf surfaces inhabitable for the fungi Phytophthora infestans, which lowers the risk of contracting late blight.

3. Bacterial Speck

Bacterial Speck
Image: Cornell University
Cause/sPseudomonas syringae pv. tomato
Symptom/sSmall black spots on the surface of the leaves
Part/s affectedLeavesFruit
Treatment / Prevention• Remove the tomato plant
• Treat the tomato seed in hot water
• Disinfect gardening tools

From the name itself, you’ll know your tomato plant is suffering from bacterial speck when you see small black spots or specks on the surface and underside of the leaves. 

Bacterial speck is caused by the bacteria Pseudomonas syringae pv. Tomato. It’s usually brought into the garden due to contaminated seeds or improper transplantation.

These black spots also have a yellow ring around them and sometimes sink or rise when touched. 

But that’s not the end of the bacterial speck infestation. It also affects the growth of tomato fruits and leaves those black specks on the skin of the tomatoes. 

Ultimately, you should not consume fruits with black spots or infected by bacterial specks to avoid getting sick.

How To Fix

Remove the contaminated tomato plant. 

Get rid of all the tomato plant debris in your garden. Dispose of them completely and do not use them as compost. 

Treat the tomato seed in hot water. 

Heat the tomato seed in hot water (122°F or 50°C) for 25 minutes to get rid of the pathogen causing bacterial speck.

Disinfect gardening tools.

Make it a routine to clean your gardening tools with bleach or rubbing alcohol to prevent the spread of plant diseases.

4. Alternaria Stem Canker

Alternaria Stem Canker
Image: Aggie Horticulture
Cause/sAlternaria alternata
Symptom/sBlack lesions on the edge of the leaves
Part/s affected• Leaves
• Stem
• Fruit
Treatment / Prevention• Remove the tomato plant
• Use disease-resistant tomato varieties.

Alternaria stem canker causes black lesions on the edges of the tomato plant leaves. Later on, these leaves will curl inwards and eventually wilt and die. 

The Alternaria stem canker is caused by another soilborne fungus, the Alternaria alternata. It thrives in warm temperatures and high humidity levels and commonly occurs in young plant seedlings. 

The stems of the plants also develop black spots, often beginning near the soil line upward. The fruits also develop circular yellow-green lesions. 

The fungus also creates a toxin that kills plant tissues and creates brown streaks on its vascular system. It leaves the whole plant damaged, and without life, it can no longer transport nutrients from its roots to its leaves. 

Be careful also because the spores of the Alternaria alternata can cause asthma and respiratory infections when inhaled by humans.

How To Fix

Remove the tomato plant.

The contaminated plant should immediately be removed, including its soil, as the fungus can survive and continue to spread if not changed. 

Use disease-resistant tomato varieties.

This is one of the surest ways to make sure you won’t get Alternaria stem canker again. Examples of these varieties are Husky Cherry Red, Jasper F1, Mt. Magic F1, Cupid F1, Jelly Bean Red F1, and Juliet tomatoes.

5. Bacterial Canker

Bacterial Canker
Image: Cornell Univesity
Cause/s• Clavibacter michiganensis
• Infected tomato seed
Symptom/s• Leaves with brown edges and yellow streaks
• Dark and sunken leaf veins
Part/s affected• Leaves
• Fruits
• Stems
Treatment / Prevention• Treat the tomato seeds in hot water
• Sanitize gardening tools 

Tomato plants that are infected with bacterial canker begin with the edges of the leaves turning brown and crispy. Later, the veins and the whole leaf turn black and drop to the ground.

Bacterial canker is usually caused by infected tomato seeds. Be careful because this disease spreads rapidly and can wipe out a whole field or greenhouse.

The bacteria Clavibacter michiganensis thrives in warm temperatures, high humidity, and moist areas. It’s a very resilient bacteria and can survive in the soil for 3 years. 

Bacterial Canker
Image: Cornell University

But it’s not just that. Bacterial canker also attacks the tomato plant’s fruits and stems. The bacteria cause the stems to split and display dark brown or black streaks, while the fruits grow small circular spots with yellow halos.

How To Fix

Treat the tomato seeds in hot water.

Soak the tomato seeds in hot water (122°F or 50°C) for 25 minutes to eliminate the pathogen.

Sanitize gardening tools.

Disinfect your gardening equipment regularly. Soak them in a solution of 9 parts water to 1 part germicidal bleach for 5 minutes. 

6. Septoria Leaf Spot

Septoria Leaf Spot
Image: University of Maryland
Cause/s• Septoria lycopersici
• Overwatering
Symptom/sTiny black dots on the surface and undersides of the leaves
Part/s affectedLeaves
Treatment / Prevention• Remove infected leaves
• Apply fungicide

Septoria leaf spots target the leaves of a tomato plant first, with yellow spots on the undersides, which will turn black or brown. 

This disease is primarily caused by the fungus Septoria lycopersici. The fungus thrives when the plant is overwatered with heavy rainfall or too much moisture on the tomato plant. 

You’ll know that these are Septoria leaf spots because of the light brown halo surrounding them. Thereafter, the leaves of the tomato plant will dry out and eventually fall off. 

The black areas don’t just cause damage to the plant itself; they also produce spores and spread the fungus or infestation to nearby plants.

The infection usually spreads first to the old leaves close to the ground and then to the young leaves.

Unfortunately, when your plant has been infected by Septoria, it won’t be able to bear fruit. Severe cases of the Septoria leaf disease could also hamper the plant’s ability to photosynthesize and cause it to die. 

How To Fix

Remove infected leaves.

Once you see the dark spots appearing on the leaves, remove them immediately. Make sure to wash your hands after to prevent the spread of the disease to other plants.

Apply fungicide regularly.

It’s advisable to use organic fungicides containing copper or potassium carbonate to prevent the spread of the disease. For chemical fungicides, choose those containing chlorothalonil.

7. Tomato Spotted Wilt Virus

Tomato Spotted Wilt Virus
Image: University of Florida
Cause/sThrip insect
Symptom/sBlack spots and purple veined-leaves
Part/s affectedLeaves
Treatment / Prevention• Control weed growth
• Repel thrip with silver reflective mulch

When thrips, tiny insects infected with the virus, feed on the tomato plant, they also spread the virus to them. 

The tomato-spotted wilt virus is recognizable through the leaves’ dark spots and purple veins. The young leaves high up the plant will twist and curl as these dark spots grow bigger. 

It also causes the stunted growth of the tomato plant. It may proceed to bear fruit, but expect these tomatoes to have black spots all over them.

How To Fix

Control weed growth.

Remove all weeds around the tomato plants and potential host plants of thrips such as plantains, buttercups, chickweeds, sow thistles, and dandelions. 

Repel thrip with silver reflective mulch.

These thrip insects are repelled by silver reflective mulch because of its glaring effect. Make your own by spray-painting silver on plastic sheets and securing them using U-shaped metals.

8. Fusarium Wilt

Fusarium Wilt
Image: Plant Natural Research Center
Cause/sFusarium oxysporum
Symptom/sBlack wilted leaves
Part/s affected• Leaves
• Stem
Treatment / PreventionPlant tomatoes in a new location

At first, you’ll see “lazy” wilted leaves at the bottom of the tomato plant. 

These leaves will turn yellow, brown, and then black as a sign that tissue death has already kicked in inside the poor tomato plant. And if you cut the stems lengthwise, you’ll also see the browning of their tissues. 

How To Fix

Plant tomatoes in a new location.

Avoid planting the tomato in the same location you used to plant eggplant, potato, or pepper for 4 to 6 years. These plants can all be infected by Fusarium wilt, so planting them in the same location will only help the fungi to thrive. 

9. Sooty Mold

Sooty Mold
Image: Sustainable Market Farming
Cause/sAphids
Symptom/sBlack sooty mold
Part/s affected• Leaves
• Stem
Treatment / PreventionSpray dish soap solution.

This tomato plant disease gives a dark mold looking like soot from chimneys, hence its name, on the surfaces of the leaves and stems of the plant. 

These black sooty molds are caused by a pest called aphids. They feed on tomatoes and suck all the juices, leaves, and stems, leaving behind a sooty mold that grows on the honeydew. 

The sooty mold then spreads and covers the leaves and stems of the tomato plant. 

How To Fix

Spray dish soap solution.

Make a solution of water, dish soap, and alcohol and spray it on the tomato plant to get rid of aphids in your garden.

10. Verticillium Wilt

Verticillium Wilt
Image: North Caroline State Extension
Cause/sVerticillium fungi
Symptom/sBlack leaves
Part/s affected• Leaves
• Stems
Treatment / Prevention• Use disease-resistant tomato cultivars
• Practice crop rotation

As the name suggests, this disease causes wilted leaves and stems on tomato plants. 

The Verticillium fungi affect the plant’s vascular tissue, which is essential in transporting water and nutrients from roots to leaves. 

Verticillium wilt usually affects only one side of the plant and spreads upwards. The leaves turn yellow (called chlorosis) and then black (called necrosis), which signals the death of the plant tissue.

How To Fix

Use disease-resistant tomato cultivars

Verticillium-resistant tomato cultivars are labeled “V” in their packaging. Examples of these are Amarillo F1, Astoria, Baby Cakes F1, Camelia F1, and Early Cherry tomatoes.

Practice crop rotation

Don’t plant the same susceptible crops in the same soil every year such as melons, eggplant, strawberries, and potatoes. 

During off years, you can instead plant crops, grains, or corn to reduce the fungus spread in the soil.

11. Tobacco Mosaic Virus

Tobacco Mosaic Virus
Image: North Carolina State Extension
Cause/sInfected seed or crop debris
Symptom/sMottled black areas with yellow rings on leaves
Part/s affected• Leaves
• Fruit
Treatment / PreventionRemove the infected tomato plant

The Tobacco Mosaic virus causes mottled black areas with yellow rings on the leaves of the tomato plant.

Apart from the stunted plant growth, the leaves are also malformed, reduced in size, and curled.  

The plant may still produce fruit, but these will unevenly ripen or will be smaller in size and number. 

Unfortunately, this virus spreads rapidly through the plant sap and has no known cure. It also affects other nightshade plants like peppers, potatoes, and eggplants. 

How To Fix

Remove the infected tomato plant.

Immediately remove the infected plant and dispose of all of its plant debris. Also avoid touching your tomato plant after working with tobacco products like cigarettes, cigars, or chewing tobacco. 

12. Leaf Mold

Leaf Mold
Image: Gardening Know How
Cause/sPassalora fulva
Symptom/sYellow to black spots on bottom leaves
Part/s affectedLeaves
Treatment / PreventionSanitize gardening tools

The leaf mold begins as yellow spots on the old leaves at the bottom of the tomato plant. These spots later grow larger and turn black. 

The lower leaves are the frequent target of the fungus Passalora fulva because they get wet from overhead watering or rainwater. Fortunately, those new and higher leaves tend to stay dry as they get direct sunlight. 

How To Fix

Sanitize gardening tools.

Leaf mold spreads through tools, so wash and sanitize your gardening equipment before and after use. 

How to Treat Black Tomato Leaves

How to Treat Black Tomato Leaves
Image: The Grow Network

​​

1. Apply fungicide.

Apply fungicide
Image: The Green Pinky

Fungicides are the quickest and most effective way of treating black tomato leaves. The market provides various fungicides for every kind of tomato plant disease. 

These fungicides are easy to use, requiring only to be diluted in water and then sprayed directly onto the leaves. 

There’s also a more natural solution to treat black tomato leaves – creating your own fungicide. Here’s how. 

DifficultyEasy ●○○○○
Duration15 to 30 minutes
Things You Need

• Baking soda
• Water
• Liquid soap
• Dropper
• Sprayer
How To Do

1. Prepare 4 cups of lukewarm water.
2. Mix one teaspoon of baking soda with the lukewarm water. 
3. Add two drops of liquid soap to the mixture using a dropper.
4. Transfer the solution to the sprayer.
5. Spray the homemade fungicide on the leaves and other infected parts of the plant. 
6. You can do this once a week until you see signs of improvement in your tomato plant. 

2. Remove infected plants.

Remove infected plants
Image: Tomato Bible

It’s inevitable, but you’ll have to remove the root of the problem – the infected tomato plant. 

Make sure to clean up all its parts and fallen fruits in the surrounding area. Dispose of them right away. 

Don’t leave them sitting in your yard or reuse them as compost because this will just cause the bacterial and fungal spores to grow back into the soil.

How to Prevent Tomatoes from Getting Diseases

As cliche as it may sound, prevention is always better than cure. Follow these tips to prevent your tomato plant from getting diseases in the future!

1. Choose disease-resistant tomato varieties. 

Choose disease-resistant tomato varieties
Image: Gardening Chores

Choosing disease-resistant tomato seeds is the surest way to prevent tomato leaves from turning black.

If you look at the information in the tomato seed packet, you’ll see different codes that indicate resistance to a specific disease. Here’s what those codes mean. 

CodeTomato Plant Disease
Alternaria alternata (stem canker or early blight)
E or EBEarly Blight
FFusarium Wilt
FFFusarium Wilt Races 1 and 2
FFFFusarium Wilt Races 1, 2, and 3
L or LBLate Blight
NNematodes
StStemphylium (gray leaf spot)
TTobacco Mosaic Virus
TSWVTomato Spotted Wilt Virus
VVerticillium Wilt

If the label says “ Big Beef VFFNTA Hybrid,” this means that the tomato variety is resistant to Verticillium Wilt, Fusarium Wilt Races 1 and 2, Nematodes, Tobacco Mosaic Virus, Stem Canker, and Early Blight.

2. Practice crop rotation.

Practice crop rotation
Image: UC Master Gardeners of Napa County

Crop rotation means not planting the same crop in the same part of your garden for two years. Therefore, you’ll have to rotate the crops on a three or 4-year cycle to eradicate plant diseases from your garden.

We also advise not to plant tomatoes and other crops from the nightshade family, such as potatoes, peppers, and eggplants, in the same place, even in alternate years. 

These nightshade crops share plant diseases like early and late blight, and planting them in the same area will only help propagate the bacteria or fungi. 

If possible, change all the soil in your garden. These tomato plant diseases usually stay dormant in the ground during winter but can rise from the grave and spread during the next planting season.

3. Sanitize your gardening tools.

Sanitize your gardening tools
Image: The Spruce

It’s a rule of thumb to disinfect all your garden equipment before and after using them to prevent the spread of bacterial or fungi diseases to tomato plants. 

You can use rubbing alcohol or a diluted bleach solution to clean your gardening tools. 

If you’re planning to plant your tomato in a pot or hanging basket, you could also take the extra step of bleaching the pots to remove previous contamination. 

4. Avoid overwatering.

Avoid overwatering
Image: Tomato Bible

It’s best to use the drip irrigation method. This way, water is applied directly onto the soil on the plant’s base, and the leaves remain dry. 

Take note that tomato plants love moist soil, so they need 1 to 2 inches of water per week. Just give them their water needs, and they’ll have fewer chances of getting sick. 

Keeping leaves wet becomes a breeding ground for moist-loving bacteria and fungi. So, by watering your tomato plants close to the soil, you’ll avoid splashing onto the lower leaves and prevent them from getting moist and vulnerable to infection. 

5. Ensure proper air circulation.

Ensure proper air circulation
Image: Tomato Bible

Proper air circulation between the plants should be done through adequate spacing and pruning. 

When planting, make sure your tomatoes are at least 18 to 24 inches apart. Enough space ensures less water splashing to the lower leaves or other plants, preventing the spread of bacteria and fungi.

Regularly prune the leggy bottom branches to prevent the spores of the disease-carrying bacteria and fungi from splashing onto the plant’s surface.

You should also remove the lower leaves of your tomato plants. As we’ve seen above, most plant diseases start with moist or wet lower leaves, so it’s best to take them out before it causes the spread of bacteria. 

Make sure to also control weed growth in your garden. Pluck them out before it gets near your tomato plants. 

FAQs on Black Tomato Leaves

Should I cut the black leaves off my tomato plant?


You should cut the leaves that turned black to prevent the spread of the infection to other parts of your tomato plant. 

What do yellow leaves on tomato plants mean?


Tomato plant leaves turning yellow is caused by nutrient deficiencies. This also causes stunted growth of its fruit and vegetables. 

Why are my tomato leaves turning black and curling?


High heat and low moisture cause the edges of tomato leaves to twist, curl, turn black, and eventually die. 

What is the best fungicide for tomato plants?


Fungicides with the active ingredient chlorothalonil are recommended for tomato plants because they cure various plant diseases, such as early blight. 

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