Whether planting outside or in a greenhouse, tomato plants can be affected by a number of diseases .
This list includes several common ailments that affect tomatoes and natural solutions to them.
Check over the symptoms carefully, since some ailments may look similar, particularly in early stages.
If you’ve had any diseases like these in the past, use this guide to identify and treat them naturally, especially for heirloom tomato varieties.
You’ll find a lot of information in this article. Be sure to pin or bookmark it for future use so you can revert whenever you have tomato plant problems.
1. Leaf Curl
Tomato leaf curl is an easy disease to diagnose. Mature plants will have their leaves curl from the outside to the centers.
It’s caused by high temperatures, too much water in the soil, and too much pruning.
Thankfully, it doesn’t affect the taste of the tomatoes. It can be avoided by making sure your soil drains well and avoiding the temptation to over-prune.
2. Septoria Leaf Spot
Brown spots on tomato leaves represent the Septoria leaf spot, which is characterized by circular, water-soaked lesions on infected leaves. These spots turn brown with gray centers before drying.
Severe infection will kill the whole leaf. Over time, the leaves will turn yellow and eventually dry out and fall off. A decline in leaves will weaken the plant causing it to stop producing fruits.
The disease can survive in the remains of previous crops, so proper cleanliness practices are important. Also, avoid overhead watering — it can help spread the fungus that causes it.
3. Leaf Mold
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Leaf mold is characterized by yellow on the upper side of older leaves. Underneath these spots is a purple or olive-green patch of mold.
Infected leaves will turn yellow and fall off. Wind can spread the mold, and high humidity and temperatures encourage mold growth.
Infections can be severe in greenhouses and the fungus can also affect blossoms, fruits, and stems.
Consider rotating crops with other vegetables. Stake and prune plants for better air circulation and avoid wetting the leaves.
BioSafe is also an excellent preventive and curative organic treatment against leaf mold fungus and other tomato leaf diseases.
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Anthracnose is an easy one to spot. Near the blossom end of the tomato, you will find a dark, bull’s eye spot that will be sunken and mushy.
If you cut open the fruit, the area under the spot will look rotten.
This is caused by a fungus that thrives in hot, humid weather. It can be spread by overhead watering that splashes the fungus from infected soil or other plants onto the plants.
It can be prevented by using watering that drips onto the roots as well as harvesting earlier since it doesn’t tend to affect tomatoes early in the ripening process.
Also, plant your garden in a sunny area and keep it weed-free. Cage or stake tomato plants to improve air circulation and prevent it.
BioSafe is a natural treatment for tomato fungus.
5. Fusarium Wilt
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Fusarium wilt is wilt that occurs quickly and watering doesn’t help.
The plant will look healthy, and then they start to wilt. It might only affect half the plant at first, but will quickly spread to the whole plant and quickly kill it.
It’s caused by the fungus Fusarium oxysporum f.sp. lycopersici and it can survive in the soil over the winter .
This nasty fungus is best prevented by crop rotation and using an organic bio-fungicide such as Mycostop.
6. Verticillium Wilt
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Verticillium wilt is caused by the soil fungus Verticillium albo-atrum and Verticillium dahliae . It attacks the root and prevents the flow of nutrients and water up to the leaves.
Older leaves on plants infected with the disease will turn yellow at the leaf margins before turning brown. Plants are stunted and wilting isn’t helped by watering.
It develops rapidly in cool weather. It isn’t easy to deal with — the most effective option is crop rotation.
7. Early Blight
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Early blight of tomato is characterized by large black spots surrounded by wide areas of yellow spots on tomato plant leaves. The leaves will have a characteristic pattern described as an oyster shell or bullseye.
To prevent it, avoid wetting leaves. Warm, wet weather increases the chances of infection and spreads it faster.
As it is caused by a fungus, if you’ve had a similar problem with your tomatoes or related plants like potatoes or peppers, you can have it again.
Crop rotation, Cueva, and avoiding planting related plants nearby can help deal with early tomato blight.
8. Late Blight
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Late blight of tomato is characterized by lesions that appear wet on the leaves that eventually turn a papery brown.
Fruit lesions are large greenish-brown patches with a greasy appearance. It tends to appear during cool, wet weather and can affect any part of the plant.
Keeping your plants away from other relatives like potatoes, peppers, and eggplants can help. Also, keep foliage fry and plant garden in a sunny area.
9. Mosaic Virus
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The tobacco mosaic virus can affect tomatoes despite the name. The leaves will be dappled with yellow and new growth will be twisty, resembling ferns.
Insects such as aphids can transmit it. To effectively control the spread, destroy plants as soon as the disease is noticed.
Be sure to wash your hands thoroughly after touching an infected plant and sterilize any equipment.
ZeroTol, a 3-in-1 organic fungicide, algaecide, and bactericide has also proven to control and reduce the spread of the tobacco mosaic virus.
10. Blossom Drop
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Blossom drop is fairly self-explanatory — blossoms will grow on your plant but will drop off before maturing.
It can be caused by temperature fluctuations, too little water, insect damage, improper nitrogen levels, or lack of pollination.
You can’t change the weather, but you can have your soil tested, and make sure to water properly and plant milkweed or similar plants to draw pollinators.
Be sure you water deeply as well and use high nitrogen fertilizers such as alfalfa meal, bat guano, fish meal, and seaweed.
11. Blossom End Rot
Your plant will look healthy, but the tomatoes will have a dark patch on the blossom end. The fruit will be mealy if you cut it open.
This is a sign of calcium deficiency in plants or improper soil ph. that is inhibiting calcium absorption.
Get a soil test kit at your local garden store. If calcium is low, you can either add eggshells to your compost or apply rock mineral compounds to raise calcium.
Check your local organic gardening center for advice. Also, be sure to water evenly to help prevent issues.
Be sure to apply organic fertilizers or compost regularly throughout the growing season as well, since the plants need a lot of nutrients to grow.
12. Damping Off
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Damping off is a fungal disease that can cause a sudden collapse of seedlings or a failure to germinate in seeds.
The stem base generally looks cut off or pinched. Seedlings generally wilt and die soon after emerging from the soil.
To help prevent it, seeds should be planted when soil temperatures are ideal and pre-soak seeds to help speed germination.
If you’re using a potting mix, be sure to use sterile potting soil that has undergone heat processing, and plant in containers.
Also, make sure your soil dries out between waterings, and avoid starting seeds in soil that is rich in nitrogen.
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Plants affected by sunscald will look healthy, and fruit develops normally.
However, as the fruit ripens, yellow patches form that turn papery and give the fruit an unpleasant look and taste.
It’s caused by too much sun exposure. The best thing to do is avoid over-pruning, and consider using a cage over stakes since they tend to provide more sun protection.
Water on the plants and fruit magnifying the sun can also cause damage. Leave plenty of foliage to protect your fruit.
14. Bacterial Speck
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Bacterial speck is found on many parts of the plant.
Affected leaves will have black or brown necrotic spots surrounded by yellow halos. You may also notice white borders around spots.
It is more severe if the leaves get wet. Avoid getting the leaves wet, so don’t use sprayers to water your plants.
Drip systems are a good solution to prevent many tomato plant diseases. An organic copper fungicide such as Cueva may also be applied at the first sign of symptoms.
15. Bacterial Spot
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The bacterial spot appears as dark, water-soaked spots that eventually turn black and drop out, leaving holes in the leaves.
Raised black specks become scab-like spots on the fruit. Good sanitation, crop rotation, and careful transplanting can help prevent infection.
16. Bacterial Canker
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Bacterial canker is easily detected by leaves that wilt and die, drying while still attached to the stem. Vascular tissue is discolored and a yellow slime can be squeezed from affected stems.
Fruit will have yellow dots as they ripen. You will see a dark rim around these spots if you check closely.
Prevention involves crop rotation, and be careful not to replant tomatoes in the same soil for at least three years.
Remove infected plants immediately and don’t compost them since that can spread the infection. Also, practicing good cleaning of tools and other equipment can help prevent the spread of it.
17. Spotted Wilt Virus
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Leaves will show yellow speckling. Growing tips may die. The fruit is malformed with green, red, and yellow bullseye spots.
Tomato spotted wilt virus is caused by thrips — tiny harmful flying insects. Check new plants carefully and practice good pest control to help get rid of thrips.
Elimination of infected plants is very effective in controlling it. Clean cultivation is very important as well.
18. Fruit Crack
Fruit cracks are exactly what it says, cracks appearing in the fruit. It tends to be caused by heavy rain after a dry spell. The tomatoes will take up too much water and crack.
The best solution is to keep up on watering so they won’t absorb too much rainwater.
However, this generally isn’t too much to worry about — the fruits are edible so long as you cut off the cracked areas.
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Catfacing results in deformed-looking tomatoes. It’s caused by the same factors as blossom drop, however, the blossom is pollinated before the petals drop.
These petals can stick to the developing fruit and cause the typical bumpy look of catfacing.
As it’s caused by low temperatures at night, the best solution is to be sure to plant later in the season.
You can also cover the soil in black plastic. The black plastic will trap heat during the day and release it back to the plants at night.
You can also try devices like a ‘wall of water’. It’s a circle or plastic tube filled with water that can help raise temperatures near your plants at night.
20. Powdery Mildew
White spots on tomato leaves represent powdery mildew. It can also be characterized by yellow spots covered with a gray powder on the surface of the spots.
The leaves will die but typically stay attached to the stem. Warm, dry conditions make it worse.
21. Pith Necrosis
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Pith necrosis is caused by the bacterium Pseudomonas corrugata .
It might not always be visible externally, but it causes the pith of the stem to turn brown and eventually die, leaving hollow spaces that can cause collapse.
This is more common in greenhouses but can be found in field-grown tomatoes and other areas where conditions are humid.
Excessive nitrogen can cause it, so be cautious. Plants can recover if conditions improve. The best treatment is to avoid planting during cool, wet weather to help avoid it.
22. Buckeye Rot
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Buckeye rot of tomato is caused by a fungus that leaves a brown or green stain-like spot that resembles a buckeye. It can also affect relatives like peppers and eggplant.
Avoid soil contact with the fruit to help prevent infection. This can be done by applying mulch.
Also, water less frequently but with a higher amount and ensure your soil drains well. Make sure to rotate crops as well or consider raised beds or container gardening.
23. Southern Blight
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Southern blight is seen as a white mold growing near the soil line. It can completely circle the stem with dark round spots that discolor both the outer and inner stem.
It can cause young plants to collapse completely. Be sure to keep up good crop rotation and remove plant debris after harvest.
Appling a high-quality, cold-pressed Neem Oil such as Rango can help control it.
24. Root-knot Nematodes
Root-knot nematodes are microscopic worms that live in the root of plants or the soil.
They can be spotted when the wilted plants are uprooted and there are swollen areas in the root balls.
You can either relocate the garden to an area that is free of nematodes or add parasitic nematodes to help decrease occurrences.
25. Gray Leaf Spot
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Gray leaf spot develops first on the underside of the leaf.
You’ll see small brownish-black specks that will grow in larger necrotic areas that may drop off, leaving a shot hole type appearance. A grayish-brown color will appear as the spots get larger.
Spots may also have a yellow halo, and severe infections can cause leaf drop, yellowing, and defoliation. Fruit production will be blighted.
The fungus can survive on weeds in the same family, so keep up on weeding. Leaf moisture can make the infection more severe.
CEASE organic fungicide can help suppress gray leaf spots and other tomato leaf ailments.
When you’re dealing with tomato issues, please note that not all color changes may be linked to plant diseases. You have to examine the plant carefully for patterns and color combinations.
For example, yellowing leaves may be caused by magnesium deficiency where the leaf would become yellow and wilt before falling. The deficiency of magnesium can be resolved by using Epsom salt.
Advice from your local organic gardening center can be very helpful as well. Good sanitation of your tools and hands can help prevent disease spread, as well as crop rotation.
Avoid planting related crops nearby and be careful when you bring in new plants. Also, be sure not to compost any infected plants or parts so you don’t spread anything further.