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 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
| Cause/s | • Alternaria tomatophila • Alternaria solani |
| Symptom/s | Black lesions with concentric circles |
| Part/s affected | • Leaves • Stem • Fruit |
| Treatment / Prevention | Remove 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
| Cause/s | Phytophthora infestans |
| Symptom/s | • Black spots on edges of lower leaves • White mildew dots above dark spots |
| Part/s affected | • Leaves • Stem • Fruit |
| Treatment / Prevention | Apply 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
| Cause/s | Pseudomonas syringae pv. tomato |
| Symptom/s | Small black spots on the surface of the leaves |
| Part/s affected | LeavesFruit |
| 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
| Cause/s | Alternaria alternata |
| Symptom/s | Black 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
| 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.
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
| Cause/s | • Septoria lycopersici • Overwatering |
| Symptom/s | Tiny black dots on the surface and undersides of the leaves |
| Part/s affected | Leaves |
| 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
| Cause/s | Thrip insect |
| Symptom/s | Black spots and purple veined-leaves |
| Part/s affected | Leaves |
| 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
| Cause/s | Fusarium oxysporum |
| Symptom/s | Black wilted leaves |
| Part/s affected | • Leaves • Stem |
| Treatment / Prevention | Plant 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
| Cause/s | Aphids |
| Symptom/s | Black sooty mold |
| Part/s affected | • Leaves • Stem |
| Treatment / Prevention | Spray 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
| Cause/s | Verticillium fungi |
| Symptom/s | Black 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
| Cause/s | Infected seed or crop debris |
| Symptom/s | Mottled black areas with yellow rings on leaves |
| Part/s affected | • Leaves • Fruit |
| Treatment / Prevention | Remove 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
| Cause/s | Passalora fulva |
| Symptom/s | Yellow to black spots on bottom leaves |
| Part/s affected | Leaves |
| Treatment / Prevention | Sanitize 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
1. Apply fungicide.
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.
| Difficulty | Easy ●○○○○ |
| Duration | 15 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.
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.
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.
| Code | Tomato Plant Disease |
| A | Alternaria alternata (stem canker or early blight) |
| E or EB | Early Blight |
| F | Fusarium Wilt |
| FF | Fusarium Wilt Races 1 and 2 |
| FFF | Fusarium Wilt Races 1, 2, and 3 |
| L or LB | Late Blight |
| N | Nematodes |
| St | Stemphylium (gray leaf spot) |
| T | Tobacco Mosaic Virus |
| TSWV | Tomato Spotted Wilt Virus |
| V | Verticillium 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.
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.
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.
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.
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
You should cut the leaves that turned black to prevent the spread of the infection to other parts of your tomato plant.
Tomato plant leaves turning yellow is caused by nutrient deficiencies. This also causes stunted growth of its fruit and vegetables.
High heat and low moisture cause the edges of tomato leaves to twist, curl, turn black, and eventually die.
Fungicides with the active ingredient chlorothalonil are recommended for tomato plants because they cure various plant diseases, such as early blight.
