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Tomatoes are one of the easiest garden crops to grow, producing an abundance of deliciously sweet fruits all summer long. But did you know that there are a bunch of tomato plant diseases just waiting to wreak havoc on your crop? Many of these diseases take advantage of weak plants in less-than-ideal growing conditions, spreading quickly and ruining your horticultural efforts.

To maximize your chances of an abundant tomato crop, we’ve found out everything you need to know about the most common tomato plant diseases, including how to prevent them and what action to take if they do occur. Let’s take a look!

1. Anthracnose (Colletotrichum spp.)

Red rotten tomatoes on plant in the vegetable garden. Tomato plants with disease.
Image Credit: Deposit Photos

Anthracnose is a fungal disease that spreads quickly in moist conditions. It causes dark lesions on all parts of the tomato plant and can lead to widespread fruit rot. To prevent it from affecting your tomato plants, keep tomato plants well-ventilated, avoid overhead watering, and harvest tomatoes as soon as they are ripe.

Treatment: There are no effective treatments for anthracnose – affected plants should be removed and destroyed.

2. Bacterial Canker (Clavibacter michiganensis subsp. michiganensis)

Rotten red tomatoes on plant in the vegetable garden. Tomato plants with disease.
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Bacterial canker spreads rapidly, causing all parts of the tomato plant to wilt and turn yellow. Plant stems split, and the fruits develop ugly brown lesions. Bacterial canker is spread via contaminated tools, so it is important to sanitize equipment regularly. Copper-based bactericides can be used in high-risk areas.

While there is no effective treatment, affected plants should be removed and destroyed.

3. Bacterial Spot (Xanthomonas campestris pv. vesicatoria)

Rotten unripe tomatoes on plant in the vegetable garden. Tomato plants with disease.
Image Credit: Deposit Photos

Bacterial spot disease appears as small, wet-looking lesions on all parts of the tomato plant. This disease spreads rapidly in warm, humid conditions. To prevent this disease from impacting your plant, keep humidity low by increasing ventilation and avoiding overhead watering. Copper-based preventative treatments can be useful in high-risk areas.

4. Blossom End Rot

Disease of tomatoes. Blossom end rot on the fruit. Damaged red tomato in the farmer hand. Close-up. Crop problems. Blurred agricultural background. Low key.
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Blossom end rot is caused by calcium deficiency or irregular watering, leading to dark and soft fruits at one end. To prevent this disease, it’s important to water regularly to maintain consistent soil moisture and sprinkle crushed eggshells around the base of plants.

If blossom end rot is present, apply a calcium-based fertilizer and increase the frequency of watering. Remove and compost any affected fruits.

5. Early and Late Blight (Alternaria solani, Phytophthora infestans)

Tomatoes get sick by late blight. Close up on Phytophthora infestans is an oomycete that causes the serious tomatoes disease known as potato blight.
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Blight is a devastating tomato disease that many growers have encountered. Both early and late blight cause yellow-brown lesions on the leaves and stems, causing plants to collapse and fruits to rot. The best way to prevent this from happening to your tomato plants is to ensure they are well-spaced and prune lower leaves to increase air circulation. Avoid watering from above and keep growing areas well-ventilated.

Treatment: It can be hard to save tomato plants affected by blight, but removing affected leaves in the early stages of the disease can sometimes be effective. In severe cases, the plants should be removed and destroyed.

6. Fusarium Wilt (Fusarium oxysporum f. sp. lycopersici)

Fusarium wilt disease on tomato plant. Damaged by disease and pests of tomato leaves.
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Fusarium wilt is a soilborne fungal disease that causes the lower leaves of tomato plants to wilt and turn yellow. As the disease progresses, the plant will lose any developing fruit and stunt new growth. Crop rotation can help prevent a buildup of fungal spores in the soil. Clear plastic placed over the soil in full sun for a month will kill existing fungal spores.

7. Gray Mold (Botrytis cinerea)

Grey mold on tomato.
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Gray mold causes grayish-brown fuzzy growth on the leaves, stems, and fruit of tomato plants. Gray mold spreads through airborne spores and thrives in cool, humid conditions. If you notice this tomato disease, remove and destroy affected leaves and treat the remaining foliage with an organic fungicide containing copper or sulfur.

8. Mosaic Viruses

Ill tomato
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Three mosaic viruses affect tomato plants – tomato mosaic virus, cucumber mosaic virus, and tobacco mosaic virus. All three cause a characteristic mottled pattern on the leaf surface. Mosaic viruses are spread by aphids and contaminated tools.

It’s best to use companion plants to attract beneficial insects that control aphid populations.

9. Powdery Mildew (Leveillula taurica)

Fungal plant disease Powdery Mildew on a tomato leaf. White plaque on the leaf. Infected plant displays white powdery spots on the leaf. Close up.
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Powdery mildew causes a white, powdery growth on all parts of the tomato plant. The leaves will become distorted and fruit will drop prematurely. This fungal disease spreads quickly via airborne spores. If you notice this disease, remove and destroy infected leaves then apply a sulfur-based fungicide.

10. Root-Knot Nematodes (Meloidogyne spp.)

Closeup hands in gloves uproot sick tomato plant.
Image Credit: Deposit Photos

Root-knot nematodes are microscopic worms that infect the roots of tomato plants. The roots become deformed and struggle to provide the plant with sufficient water and nutrients, resulting in stunted growth and wilting. The best preventative measure is to avoid growing tomatoes in the same area year after year – crop rotation prevents a build-up of nematodes in the soil.

Protect Your Tomatoes From 15 Pests That Can Wreak Havoc on Your Crop

 11. Septoria Leaf Spot (Septoria lycopersici)

The last of the bounty.
Image Credit: Deposit Photos

Septoria leaf spot is a fungal disease that causes small circular lesions with dark borders on the lower leaves of tomato plants. The plant quickly becomes weakened, and crop yields are poor. To prevent this disease, it’s best to water early in the day and avoid splashing the leaves. To conserve moisture, mulch around the base of plants. Treat the plant with a copper-based fungicide. 

 12. Southern Blight (Sclerotium rolfsii)

Wilting tomato leaves on a vegetable garden in australia in spring.
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Southern blight causes the stem of tomato plants to turn yellow and rot close to the ground, resulting in complete loss of the plant. It is spread through infected soil and plant debris. The best way to prevent this is to keep the soil around tomato plants clear and free from plant matter.

13. Tomato Spotted Wilt Virus (TSWV)

Organic tomato plant and fruit on a natural background.
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Tomato spotted wilt virus is spread by thrips and causes characteristic rings on developing fruit. You may also see dark spots on the leaves and stunted growth.

As there is no cure for this virus, affected plants must be removed and destroyed. Control thrips by attracting beneficial predators such as lacewings, parasitoid wasps, and ladybugs.

14. Tomato Yellow Leaf Curl Virus (TYLCV)

Close-up of curled leaves on tomato plants in a vegetable patch. Tomato leaf curl, a common problem in UK gardens.
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Tomato yellow leaf curl virus is spread by whiteflies and causes upward curling and yellowing of tomato plant leaves. While there is no effective treatment, it’s simply best to remove and destroy any affected plants and Control whitefly populations with insecticidal soap or neem oil.

15. Verticillium Wilt (Verticillium spp.)

Tomato disease.
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Verticillium wilt is a soilborne fungal disease that causes wilting and yellowing, often only on one side of the plant. If verticillium wilt is prevalent in your area, grow resistant varieties (marked with a ‘V’ on the label).

In addition, this soilborne pathogen can only be eradicated by soil fumigation. All affected plants should be removed and destroyed.

 16. White Mold (Sclerotinia sclerotiorum)

Tomato mold.
Image Credit: Deposit Photos

White mold causes a cotton-like fungal growth on tomato plants’ stems, leaves, and fruit. To prevent white mold, maintain a good crop rotation schedule, keep plants well-ventilated, and avoid overhead watering. Organic treatments such as Coniothyrium minitans can get rid of spores in the soil.

17 Plants That Will Keep Squirrels From Eating Your Garden

squirrel with tomato
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To help you safeguard your garden, we’ve handpicked 17 plants Squirrels tend to avoid due to their taste, smell, or texture.

17 Plants That Will Keep Squirrels From Eating Your Garden

How to Support Tomatoes: Tomato Stakes vs. Tomato Cages

supporting tomatoes with stakes or cages
Image Credit: Homestead How-To

Supporting garden tomatoes with tomato stakes or cages is necessary for all but a few varieties of tomatoes. Without some form of support, your tomato plant will sprawl out over the ground. Here, we’ll share some considerations to help you make a choice that will work for your garden.

How to Support Tomatoes: Tomato Stakes vs. Tomato Cages

How to Properly Prune Tomato Plants

tomato plants in garden
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If you’re dealing with tomato plants that often get diseased, tend to droop, or look unhealthy, pruning should be on your gardening checklist. Here’s how you can properly prune your tomato plants.

How to Properly Prune Tomato Plants

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