10 Common Tomato Diseases and How to Treat Them

Three tomatoes showing signs of disease — Damage without the presence of insects or worms often means disease, not pest infestation; though you can certainly have both, and insects can be the spreaders.

While most tomato pests are visible to the naked eye, you can’t exactly see the cause of tomato diseases, but you can see the symptoms that tomato diseases leave behind, such as leaf spots, brown foliage, or prematurely rotted fruit. Noticing these telltale signs of plant diseases can help you determine what’s going on with your tomatoes and make it easier to treat or prevent diseases from spreading.

1. Septoria leaf spot

Tomato with Septoria leaf spot — Some diseases, like Septoria leaf spot, may not be fatal, but they can weaken a plant to the point of low production and slow growth.

Septoria leaf spot is a very common tomato disease, but it can affect other members of the nightshade family as well. While this disease usually isn’t fatal to tomatoes, it can rapidly defoliate plants, weakening them and slowing their growth. When tomato leaves drop due to septoria leaf spot, it can also expose tomatoes to the bright sun, increasing the chances of sunscald.

Septoria leaf spot is caused by the Septoria lycopersici fungus, and it often appears on older tomato leaves first. When septoria leaf spot strikes, tomato leaves often develop small, gray, or tan dots with dark margins, and the spots get larger over time. This disease is particularly problematic when the weather is warm, and the air is humid.

Like many other fungal diseases, septoria leaf spot can overwinter in the soil or in old plant debris, and it often spreads when plants are watered either with a hose or rain. Water droplets can splash fungal spores onto tomato leaves, increasing the spread of the fungus. Insects, humans, and unsterilized garden equipment can also spread septoria leaf spot.

Currently, there aren’t any tomato varieties that are fully resistant to septoria leaf spot, although some tomato types are less susceptible. Performing proper garden maintenance, rotating your crops, and destroying infected plant matter can limit septoria leaf spot in your garden. Keeping your soil well-mulched and trimming away lower tomato leaves will also prevent fungal spores from splashing up on your plants from the soil.

2. Fusarium wilt

Tomatoes with Fusarium wilt — Top-down wilting that occurs despite good watering practices is a reason to suspect Fusarium wilt.

Fusarium wilt is another devastating tomato disease that’s caused by a fungus (Fusarium oxysporum), and it can weaken or kill tomato plants over time. When the fusarium fungus enters tomato plants through their roots, it travels inside the tomato tissue and clogs up the plant’s xylem. When this occurs, tomatoes can no longer transport water, and they can wilt dramatically, even when their soil is moist.

Most often, fusarium affects the tops of tomato plants first, and you’ll notice sections of the plant will look wilted during the day, but they’ll appear to recover in the evening. As the infection progresses, the wilted sections of the plant will spread, and the plant will remain wilted even at night. Like many other tomato diseases, fusarium wilt affects tomatoes, as well as other nightshade plants and legumes too.

One solution for preventing fusarium wilt is to only grow tomato varieties that are resistant to this pathogen. While this often works, if tomato plants are stressed by root-knot nematodes, even resistant tomato varieties can still succumb to fusarium wilt. Rotating your crops, practicing good garden maintenance, disinfecting garden tools, and raising soil pH levels can all reduce the chances that fusarium wilt will crop up in your garden.

3. Anthracnose

Tomatoes with anthracnose infection — Like many tomato diseases, anthracnose is a fungal disease that thrives in warm and humid conditions.

Tomatoes can be susceptible to various types of rot, but anthracnose is one of the most common causes. This disease is caused by a naturally occurring fungus (Colletotrichum spp.), and it results in tomatoes developing large, sunken, soft spots, which can grow larger and darker over time. Often, anthracnose rot occurs on ripe tomatoes, but it can also creep into underripe green tomatoes, and it can spoil entire harvests.

Like most other fungal diseases, anthracnose thrives in warm, humid conditions, and it can overwinter in garden soil. Watering can splash the fungal spores onto tomato leaves and fruit, spreading the fungus throughout your plants. Contaminated garden tools and harvesting can also promote anthracnose.

Some tomato varieties are naturally resistant to anthracnose, and purchasing these cultivars can prevent this disease from entering your garden space. Following proper garden maintenance protocols, rotating your crops, and staking tomatoes to improve airflow are also helpful. Additionally, whenever you can, water your tomato plants at the soil line to avoid wet leaves and fruit, which are more likely to develop fungus.

4. Verticillium wilt

Tomatoes with Verticillium wilt — Verticillium wilt is a condition similar to Fusarium wilt that occurs in cool, wet weather.

Verticillium wilt acts similarly to fusarium wilt; however, fusarium wilt is more of a problem in warm, dry conditions, while verticillium wilt usually occurs in cool and wet weather. As with other fungal diseases, verticillium can overwinter in garden soil and old plant debris. Purchasing resistant tomato seeds is one of the best ways to prevent verticillium wilt, as fungicides don’t work on this disease.

Verticillium wilt is caused by several strains of the verticillium fungus, and it enters plants through their root systems. As with fusarium wilt, this fungus clogs the xylem of plants and causes them to wilt. Beyond this, verticillium wilt can stunt plants and their fruit, cause leaves to yellow and drop, and it can also darken the vascular tissue of tomato plants, resulting in streaked stems and curled leaves.

Since there is no treatment for verticillium wilt, this disease is managed by prevention only. Beyond purchasing resistant seed varieties, proper garden maintenance is key for keeping wilt out of your garden. Always rotate tomato crops, destroy diseased plant material, and disinfect garden tools in between plants.

5. Early blight

Early blight on tomato plants — Early blight spreads from fungal spores that splash up from soil, as well as from insects that spread the disease, like flea beetles. Mulches can help control soil splash to control disease.

If you’ve been growing tomatoes for any length of time, chances are you’ve already encountered early blight. This tomato disease is very common, and it often doesn’t kill tomato plants, although it can spoil fruit and diminish harvest yields. Early blight can occur throughout the growing season, but it is most prevalent in hot and humid weather.

Early blight is caused by a fungus (Alternaria solani) that can spread into gardens from infected plant debris, seeds, or transplants. Once established, early blight can overwinter in soil, and it can spread when plants are watered, and soil splashes up on plant leaves and fruit. Flea beetles are also a common vector for early blight, which is another reason to keep these pests out of your garden!

Early blight usually occurs on lower leaves and causes leaves to turn yellow and develop dark spots. Spots can also appear on infected tomatoes, and spots caused by early blight usually display distinct concentric rings. Garden maintenance, organic fungicides, resistant tomato varieties, staking, and pruning to increase airflow around your plants are all solutions for early blight.

6. Late blight

Tomatoes with late blight — Late blight spreads over distances through infected water. Overhead watering is also a contributor that can rapidly spread and exacerbate disease.

One of the most infamous crop diseases of all time, late blight, is caused by a water mold (Phytophthora infestans), rather than a soil-dwelling fungus, and it was the disease behind the Irish potato famine. Unlike many other tomato diseases, late blight doesn’t just cause aesthetic issues and leaf damage. Late blight affects both tomatoes and potatoes, and it can cause total crop failure, costing farmers and backyard gardeners a lot of money.

Late blight produces lots of spores that can spread over long distances, and they are particularly problematic in hot, wet conditions. Bottom watering can help slow the spread of late blight while using sprinklers and overhead watering can actually promote this disease. If late blight occurs in your garden, affected plants should be destroyed immediately to limit the disease.

Late blight usually occurs later in the season than early blight, and it can cause dark spots on plant leaves and fruit. As the disease progresses, you can usually spot the grayish fungal spores on tomato leaves, and tomatoes can turn brown and leathery. To avoid introducing late blight into your garden, always buy tomatoes from reliable suppliers and consider purchasing tomato seeds that are resistant to blight.

7. Tomato mosaic virus

Tomato plant with tomato mosaic virus — No smoking in the garden! Mosaic viruses can spread from infected smoking products and from hands after smoking such products--and there is no way to know if products are infected. Many commercial growers will not allow smoking in or near their plantings.

Tomato mosaic virus and the closely related tobacco mosaic virus produce yellow, mottled patterning on plant leaves that are said to resemble a mosaic. When infections are severe, tomato leaves may develop raised patches of dark green that have a fern-like appearance. A mosaic virus can also damage the fruit of tomato plants and cause tomatoes to develop yellow spots, sunken patches, or dark brown interiors.

Tomato mosaic virus can spread by seeds or infected plants, so you’ll always want to purchase tomato starts from reliable sources. Unfortunately, the mosaic virus can also be introduced into gardens by humans, and it can even be transmitted by handling tobacco products, or from smoke from smoking. Washing your hands after smoking or handling cigarettes can reduce the chances that the mosaic virus will arrive in your garden.

Beyond selecting resistant seed varieties, you can also limit the spread of the mosaic virus by rotating crops and destroying infected plant debris. Aphids and leafhoppers can also transmit this disease, and it can spread from certain weeds. While composting works for a lot of garden debris, don’t compost infected plant matter, as tomato mosaic virus and many other plant diseases can often survive the composting process.

8. Bacterial spot

A tomato plant with bacterial spot disease — Many tomato diseases are caused by viruses or bacteria, but bacterial spot is a bacterial disease, as its name implies.

Unlike the other tomato diseases on this list, bacterial spot is caused by bacteria (Xanthomonas), instead of fungi or viruses. When it enters garden spaces, bacterial spot can cause tomato leaves to develop dark spots that turn gray with dark centers as the spots spread. Tomatoes can also exhibit dark bumps that become sunken as a result of this devastating plant disease.

If tomatoes develop bacterial spot, it’s important to dispose of all of the affected fruit. While humans can’t be infected with bacterial spot, the disease can make it easier for other pathogens and bacteria to enter tomatoes, and you don’t want to eat that! Since it limits the spread of diseases, burning is usually the best way to destroy infected plants.

Organic fungicides can sometimes be used to treat bacterial spot, but prevention is even better. Purchasing certified, disease-free tomato seeds can ensure bacterial spot never arrives in your garden. Additionally, since bacterial spot prefers hot, humid conditions, consider staking tomatoes to improve airflow and water your plants at the soil line whenever possible.

9. Tomato yellow leaf curl virus

A tomato with yellow leaf curl virus — Tomato yellow leaf curl is a relatively new disease to many areas; know the signs so you'll recognize if this disease makes its way to you.

Tomato yellow leaf curl virus is a relatively new issue for gardeners, and it likely arrived in the United States in an international plant shipment. This disease often spreads by whiteflies, which feed on plant sap, and it can cause crop failure in commercial farms and backyard gardens.

When young tomato plants are infected, they may not fruit at all. Older plants can develop yellow leaves that curl at their margins, and plants can be stunted and drop their flowers. Herbicide exposure can also cause these issues, so it’s important to consider herbicides as a potential cause of plant symptoms before you diagnose your tomatoes with yellow leaf curl virus.

If this virus spreads into your garden, the best course of action is to destroy infected plants. You can reduce the likelihood that you’ll ever encounter this tomato disease by purchasing seeds and plants from reliable suppliers. Preventing whiteflies with companion planting or other organic pest control measures can also help!

10. Damping off

Tomato seedlings with damping off disease — Damping off disease, a fungal disease, is a common killer of young seedlings.

Damping off is a fungal disease that’s typically caused by the pythium fungus, although other fungi can result in damping-off too. This disease predominately affects young seedlings, and it can target tomatoes and other vegetables, herbs, and flowers. In the right conditions, damping off can also cause root and crown rot in mature plants, but this is less common.

When seedlings develop damping off, they can rapidly collapse and die. Upon closer inspection, affected seedlings often have soft, sunken, or mushy spots on their stems, and roots may also display signs of rot. In severe cases, damping off can prevent seeds from germinating, or it can cause entire flats of seedlings to fail.

Damping off usually occurs in warm and humid settings with minimal airflow. If you’re starting tomato plants from seed, always use fresh potting mix and sterilize all pots and watering trays each spring. Adding a fan to your growing setup can also improve airflow and prevent the chances that damping off will set in.

Other common tomato issues

White flies on a tomato plant — It helps to know the signs of insect damage and infestation along with the signs of disease so that you can treat appropriately.

Tomato diseases can definitely cause problems in the garden, but many symptoms of tomato plant distress are vague, and they can also be attributed to pests or environmental factors. Before treating your tomatoes for pathogens, make sure that your tomatoes aren’t suffering from any of these other common issues.

Pests

Trail-like damage from insects on tomato leaves — There are few tell-tale signs that pests can leave behind, even if you do not see them.

Some tomato pests, like hornworms, are large and easy to spot. But even if you don’t see any pests on your tomatoes, it doesn’t necessarily mean your tomatoes aren’t being eaten by insects.

If you suspect pests may be targeting your plants, look your tomatoes over carefully for pests and check them for other telltale signs of predation. Ragged holes on plant leaves or fruit or leaves that have been stripped down to their veins are common signs of pests. Pests can also leave behind tiny “shot holes” on plant leaves, produce stippling patterns on leaf surfaces as they feed, or they may deposit a sticky, “honeydew” residue on your plant.

Sunscald

Sunscald can happen in any climate, but it is particularly common in very hot weather or when tomato plants have been over-pruned. Removing tomato leaves can expose the tender fruit to too much bright sun, which can cause damage. Sunscald usually appears on the upper sections of tomatoes, and it can cause pale or white spotting that turns wrinkly as the tomato matures.

Watering issues

Tomatoes that were overwatered and cracked — Be aware of the signs of under- and over-watering, like cracking (typically caused by overwatering or inconsistent watering).

Underwatered tomatoes can wilt, develop brown or crispy leaves or drop fruit. But overwatering tomato plants should also be avoided as it can result in wilting, and plants may develop yellow leaves and stems as root rot sets in. Irregular watering also stresses out tomato plants and often results in tomatoes cracking or splitting due to fluctuating water levels.

Temperature extremes

Tomato plants impacted by heat stress — Hot weather can cause tomatoes to stop producing, though they will typically recover when temperatures fall to more moderate levels.

Tomatoes are warm weather-loving plants, and they shouldn’t be planted outdoors until daytime soil temperatures reach around 60°F. Planting tomatoes out too early in the spring can cause cold stress, and affected plants will also lose leaves, or leaves can turn yellow or black and wilt.

While tomatoes generally tolerate hot weather better, if temperatures climb too high, tomatoes can drop flowers and stop fruiting. Hot temperatures also increase the chances of sunscald, and plants may droop due to water loss. Installing a shade cloth over tomatoes during very hot weather can help you avoid these issues.

Nutrient deficiencies

Tomato plants impacted by poor nutrition — As heavy feeders, tomatoes require adequate nutrition to perform optimally.

Tomatoes are heavy-feeding plants that should be fertilized throughout the growing season to support their growth. But if tomatoes don’t receive enough nutrients or they’re grown in depleted soils, they can develop various nutrient deficiencies.

Specific nutrient deficiencies can cause different symptoms in tomatoes, but in general, nutritional deficiencies result in stunted growth and poor fruit production. Plant leaves may also turn pale with visible veining.

Blossom end rot

Blossom end rot is a very common issue in tomatoes, and it can look a lot like certain plant diseases, including bacterial spot and anthracnose. However, blossom end rot results from environmental conditions, rather than pathogens.

When blossom end rot sets in, tomatoes will usually develop sunken, mushy, and dark spots on their bottoms, which can even occur on green fruit. While this issue can be caused by soil that’s deficient in calcium, it’s more likely to result from irregular watering practices. To learn more, check out our full guide on how to prevent and treat blossom end rot here.

Herbicide exposure

Yellowed and dying tomato plants exposed to herbicides — Herbicide exposure can look a lot like disease like yellow leaf curl virus, and it is becoming increasingly difficult to avoid, especially if you bring in new soil, compost, or material.

Herbicides can kill pretty much any plant they come in contact with, so it’s best to avoid spraying herbicides near your garden. Overspray or drift can cause herbicides to spread to non-target plants, which can kill or severely damage them. Herbicides can also enter into gardens in fill or compost that was made with treated plants or manure from livestock that ate treated hay.

Herbicide exposure in tomatoes can mimic some plant diseases, especially the tomato yellow leaf curl virus. Affected plants may wilt or turn yellow, and their leaves often become distorted or curled. Tomatoes can also be damaged and exhibit signs of necrosis or deformed growth.

Frequently asked questions

A tomato affected by rot — Tomatoes from plants with diseases are safe for humans to eat, but getting the fruit to maturity and ripening can be difficult without treatment.

Can you still eat tomatoes with blight?

Tomatoes with blight are still perfectly safe to eat, but you may not get a chance to harvest them. Since blight causes tomatoes to rot on the vine, it can limit your harvest and prevent tomatoes from maturing properly.

Is it safe to eat tomatoes with a mosaic virus?

While the mosaic virus can cause a lot of problems for tomatoes and limit harvest yields, the tomatoes of affected plants are still edible.

Can you eat tomatoes with wilt?

Tomatoes infected with wilt are safe to eat. Still, wilt will severely impact your harvest, and it may prevent tomatoes from ripening properly.

Does tomato blight stay in the soil?

Early blight can overwinter in garden soil and infect plant material, but late blight requires plant tissue to overwinter. Late blight can, however, overwinter in plant debris, especially if your plants aren’t completely killed by winter weather. That’s why it’s so important to remove infected plant debris from your garden in autumn if you’ve dealt with late blight.

Which is the most serious disease of tomato?

While all tomato diseases cause problems, wilt and late blight are arguably the most severe tomato pathogens. Some plant diseases cause primarily aesthetic issues, or they can diminish tomato harvests, but late blight and wilt are fatal to tomato plants, and they can kill entire crop fields if left unchecked.

How do I get rid of tomato fungus?

Organic fungicides can help treat some fungal issues, like early blight. Some tomato fungi can also be treated with all-natural, organic methods, such as baking soda or milk spray.

Summary

Healthy, ripe red cherry tomatoes — Whether pest or disease, tomato problems can often be kept under control with multi-purpose organic treatments like Neem oil (both an anti-fungal and natural insecticide)

As frustrating as tomato diseases can be, you can always find a solution to whatever tomato pathogen you’re dealing with. Watering plants at the soil line is one easy way to prevent many tomato issues, and mulching can keep fungal spores from splashing up on your plants and causing problems. Starting your garden with disease-resistant tomato seeds is also helpful, and trellising tomato plants can improve airflow and reduce disease spread.

The most important thing to remember when tackling plant diseases is to not get frustrated. With time and a bit of effort, you should be able to eradicate most tomato pathogens from your garden, and you can limit the spread of diseases by acting quickly. A well-timed pruning and cleaning up of your garden in autumn may be all you need to remove tomato diseases from your yard once and for all.

For more tomato growing tips, learn how to organically treat tomato hornworm infestations with our easy guide, or discover the top tomato growing mistakes to avoid right here.