Tomato plant disease pictures

20 Common Tomato Plant Problems and How to Fix Them

If you’re one of the three million people who planted a home garden this year, you’re most likely growing tomatoes. Nine out of 10 gardeners grow tomatoes, and that number would be 10 out of 10 if the holdouts would taste a fresh garden tomato and compare it to a grocery store purchase. Nothing beats the taste of a fresh home-grown tomato!

Many gardeners who grow tomatoes, however, are frustrated with the progress of their plants. The plant may not set fruit. Or your tomatoes may ripen, but have ugly, spongy black spots at the bottom. Worse still, your plants may look great in the evening when you say goodnight to them, but in the morning, they’re skeletons waving empty branches in the breeze.

Welcome to the world of tomato problems. This list of 20 common tomato problems and their solutions will help you identify an issue — whether it’s just starting or already full-blown — and show you how to correct it, so you can save your tomato plants and harvest yummy tomatoes this year.

Identify Tomato Plant Problems and Diseases

Before diving into the list, it’s important for you to correctly identify the problem or tomato plant disease. When trying to identify tomato plant diseases, use these steps:

  1. Identify the affected part of the plant — Is it the tomato itself, the leaves, stems, flowers or roots?
  2. Note differences — When you compare your tomato plant to a healthy plant, how does yours differ? For example, a healthy tomato plant has softly fuzzed, medium-green leaves. If the leaves of your plant have brown or black patches, holes, chewed edges or fuzzy mold growing on them, make a note of that before perusing the list of problems.
  3. Look for insects — What insects do you see on your plants? If you need help identifying them, take a photo and contact your local Cooperative Extension agent to identify the insects.

Armed with this information, you can easily scan this list and narrow down the possible tomato plant disease or pest problem and how to fix it.

20 Common Tomato Problems

The list is divided into two sections: 16 diseases caused by poor cultivation habits, bacteria or fungi, and 5 insect-specific tomato problems. We have also included some tips for growing delicious, healthy tomato plants so you can keep those problems away next year.

16 Tomato Plant Diseases

Tomato diseases, garden fungi and certain environmental conditions can quickly cripple your plants. Oftentimes, you can rescue the tomato plant with a little TLC, but some circumstances may require you to destroy the plant and plant another crop in its place.

Be sure to browse the extended information below on tomato plant problems, but, overall, here are the most common disease and fungus triggers in tomato plants:

  • Not enough fertilizer. (Solution: Test your soil and apply fertilizer as appropriate for the growth stage.)
  • Over-pruning. (Solution: Always use a tomato cage and leave enough foliage to shield the fruit.)
  • Not enough calcium. (Solution: Test your soil, apply lime and gypsum as needed.)
  • Planting before temperatures raise to ideal levels. (Solution: Wait for the right planting time for your Hardiness Zone.)
  • Too much water or too little water. (Solution: Water them evenly through the growing season.)
  • Watering overhead, which promotes fungal growths. (Solution: Water at the base of the plant. and apply fungicide.)
  • Lack of air flow around plants. (Solution: When planting, space tomato plants at appropriate distance from one another and prune leaves (but not too much, see above) as they grow. Apply fungicide if powdery mildew appears.)

1. Blossom End Rot

  • What it looks like: The tomato plants appear healthy, but as the tomatoes ripen, an ugly black patch appears on the bottoms. The black spots on tomatoes look leathery. When you try to cut off the patch to eat the tomato, the fruit inside looks mealy.
  • What causes it: Your plants aren’t getting enough calcium. There’s either not enough calcium in the soil, or the pH is too low for the plant to absorb the calcium available. Tomatoes need a soil pH around 6.5 in order to grow properly. This soil pH level also makes it possible for them to absorb calcium. Uneven watering habits also contribute to this problem. Hot, dry spells tend to exacerbate blossom end rot.
  • What to do about it: Before planting tomatoes in the spring, have your local garden center or Cooperative Extension conduct a soil test. Tell them you’ve had problems with blossom end rot in the past, and they will give you recommendations on the amendments to add to your soil. Lime and gypsum may be added for calcium, but they must be added in the proper amounts depending on your soil’s condition. That’s why a soil test is necessary. Adding crushed eggshells to your compost pile can also boost calcium naturally when you add compost to the soil. A foliar spray containing calcium chloride can prevent blossom end rot from developing on tomatoes mid-season. Apply it early in the morning or late in the day — if sprayed onto leaves midday, it can burn them. Water plants regularly at the same time daily to ensure even application of water.

2. Blossom Drop

  • What it looks like: Flowers appear on your tomato plants, but they fall off without tomatoes developing.
  • What causes it: Temperature fluctuations cause blossom drop. Tomatoes need night temperatures between 55 to 75 degrees F in order to retain their flowers. If the temperatures fall outside this range, blossom drop occurs. Other reasons for blossom drop on tomatoes are insect damage, lack of water, too much or too little nitrogen, and lack of pollination.
  • What to do about it: While you can’t change the weather, you can make sure the rest of the plant is strong by using fertilizer for tomatoes, drawing pollinators by planting milkweed and cosmos, and using neem oil insecticides.

3. Fruit Cracks

  • What they look like: Cracks appear on ripe tomatoes, usually in concentric circles. Sometimes insects use the cracks as an opportunity to eat the fruit, or birds attack cracked fruit.
  • What causes them: Hot, rainy weather causes fruit crack. After a long dry spell, tomatoes are thirsty. Plants may take up water rapidly after the first heavy rainfall, which swells the fruit and causes it to crack.
  • What to do about them: Although you can’t control the rain, you can water tomatoes evenly during the growing season. This prevents them from being so thirsty that they take up too much rainwater during a heavy downpour.

4. Sunscald

  • What it looks like: The plants look healthy, and the fruit develops normally. As tomatoes ripen, yellow patches form on the red skin. Yellow patches turn white and paper-thin, creating an unpleasant appearance and poor taste.
  • What causes it: As the name implies, the sun’s rays have actually scalded the tomato.
  • What to do about it: Tomato cages, or a wire support system that surrounds the plants, give the best branch support while shading the developing tomatoes naturally. Sunscald usually occurs on staked plants that have been too-vigorously pruned, exposing many of the tomatoes to the sun’s rays. Leaving some foliage and branches provides shade during the hottest part of the day.

5. Poor Fruit Set

  • What it looks like: You have some flowers but not many tomatoes. The tomatoes you do have on the plant are small or tasteless.
  • What causes it: Too much nitrogen in the soil encourages plenty of green leaves but not many flowers. If there aren’t enough flowers, there won’t be enough tomatoes. Another cause may be planting tomatoes too closely together. Tomatoes are self-pollinating, meaning that each flower contains both the male (stamens) and female (pistils) parts. Wind typically pollinates tomatoes, but if plants are too close together, the wind can’t reach the flowers.
  • What to do about it: Have your soil tested. If you’re planting tomatoes in the spring, leave at least two feet or more between plants so that good air circulation can help pollinate them. If your plants are already in the garden, you can simply shake the flowering branches to simulate wind and get the pollen from the stamens to the pistils.

6. Catfacing

  • What it looks like: Catfacing makes tomatoes appear deformed. The blossom end is rippled, bumpy and lumpy.
  • What causes it: Plants pollinated during cool evenings, when the temperatures hover around 50 to 55 degrees F, are subject to catfacing. Blossoms fall off when temperatures drop too low. However, if the flower is pollinating before the petals begin to drop off, some stick to the developing tomato. This creates the lumps and bumps typical of catfacing.
  • What to do about it: If possible, plant tomatoes a little later in the season. Make sure the weather has truly warmed up enough to support proper tomato development. Devices such as a “Wall of Water” — a circle of water-filled plastic tubes — raise temperatures near the tomato and help keep them high enough on cold nights to prevent cold-related problems. Using black-plastic spread on the soil can also help. As the plastic heats during the day, it releases the heat back towards the plants at night. Black plastic can be used as a temporary measure until the temperatures warm up enough that it’s no longer needed.

7. Leaf Roll

  • What it looks like: Mature tomato plants suddenly curl their leaves, especially older leaves near the bottom. Leaves roll up from the outside towards the center. Sometimes up to 75% of the plant is affected.
  • What causes it: High temperatures, wet soil and too much pruning often result in leaf roll.
  • What to do about it: Although it looks ugly, leaf roll won’t affect tomato development, so you will still get edible tomatoes from your plants. Avoid over-pruning and make sure the soil drains excess water away.

8. Puffiness

  • What it looks like: The tomato plants look fine, they bloom according to schedule, and ripe red tomatoes are ready for harvest. When the tomato is sliced, the interior has large, open spaces and not much fruit inside. Tomatoes may feel light when harvested. The exterior of the tomato may have an angular, square-sided look.
  • What causes it: Under-fertilization, poor soil nutrition or inadequate pollination.
  • What to do about it: Make sure you are feeding your tomato plants throughout the season. A balanced fertilizer such as a 10-10-10 should be fed biweekly or monthly. Tomatoes are heavy feeders and need fertilizer throughout the growing season. For gardeners, frequent top-dressings with homemade compost and compost teas are a must.

9. Bacterial Canker

  • What it looks like: Often confused with cloudy spot disease, bacterial cankers start as yellow dots on ripening red tomatoes. If you look carefully at the spots — using a magnifying glass if you have one — you’ll see a dark, birds-eye-type rim around each of the yellowed spots. This is what distinguishes bacterial canker from cloudy spot disease.
  • What causes it: A bacteria called Clavibacter michiganensis. The bacteria occurs naturally but can be brought into the garden on infected plants or tools. Once it gets into the soil, rainwater splashes it up onto the plants. If there’s an open sore, such as insect damage or a leaf missing from pruning, it can enter the plant and infest it.
  • What to do about it: Remove the infected plants immediately and do not plant tomatoes again in that soil for at least three years. Rotate your crops regularly to prevent these and other diseases from taking hold in the soil. Don’t compost the dead plants — instead, put them in the trash to avoid spreading the bacteria.

10. Anthracnose

  • What it looks like: As tomatoes ripen, a dark, bull’s-eye circle appears on the blossom end or bottom of the tomato. The spot is sunken and mushy to the touch. When you slice into the tomato, there’s a black mushy spot underneath that looks like rot.
  • What causes it: A fungus called Colletotrichum phomoides. The fungus loves hot, moist weather and is often spread by overhead irrigation, sprinklers striking infected soil and splashing the fungus up onto the plants, and infected plants.
  • What to do about it: Switch your watering methods so water drips on the roots, not the leaves of the plants. Harvest tomatoes when ripe, since overly ripe tomatoes tend to contract the fungus more than tomatoes in the early stages of ripening.

11. Early Blight

  • What it looks like: You’ll find brown spots on tomato leaves, starting with the older ones. Each spot starts to develop rings, like a target. Leaves turn yellow around the brown spots, then the entire leaf turns brown and falls off. Eventually the plant may have few, if any, leaves.
  • What causes it: A fungus called Alternaria solani. This fungus can live in the soil over the winter, so if your plants have had problems before like this, and you’ve planted tomatoes in the exact same spot, chances are good the same thing will happen to your plants this year.
  • What to do about it: Crop rotation prevents new plants from contracting the disease. Avoid planting tomatoes, eggplants or peppers in the same spot each year as these can all be infected with early blight. A garden fungicide can treat infected plants.

12. Septoria Leaf Spot

  • What it looks like: After the plants begin to develop tomatoes, the lower leaves break out in yellow spots. Within the yellow spots, dark gray centers with dark borders appear. Black dots appear in the center of the spots. Foliage dies and falls off.
  • What causes it: A fungus called Septoria lycopersici thatinfects foliage.
  • What to do about it: Avoid watering tomatoes from the top, as the spray can force the spores developing on the leaves back into the soil and continue the disease cycle. Certis Double Nickel 55™ Fungicide & Bactericide was developed for use against Septoria Leaf Spot on tomatoes.

13. Fusarium Wilt

  • What it looks like: Your tomato plants look fine, when suddenly, they start to wilt. At first, only one side may be affected, but then the whole plant is wilting. You water them, and the problem gets worse. Within a day or two, the plant is dead!
  • What causes it: A nasty fungus called Fusarium oxysporum f.sp. lycopersici that attacks the vascular system of the plant, roughly equivalent to a human’s veins. The fungus destroys the xylem tubes, which transport water and nutrients up from the roots and into the leaves.
  • What to do about it: In the case of fusarium wilt, the best defense is a good offense. Rotate your crops so tomatoes aren’t planted in the same section of the garden each year. Purchase wilt-resistant varieties if you’ve lost tomatoes to wilting diseases in the past, since the fungus can overwinter in garden and lawn soils.

14. Verticillium Wilt

  • What it looks like: Yellow blotches appear on the lower leaves. As the blotches spread, the veins in the leaves turn brown. After the leaves turn brown, they fall off. The disease progresses up the stem until the plant is stunted.
  • What causes it: A fungus that lives in the soil, Verticilliurn albo-atrum, attacks the roots and travels up the xylem tubes with water. It then prevents the normal flow of water and nutrients to the leaves.
  • What to do about it: Once plants are infected, there isn’t much you can do to treat Verticillium wilt. Rotate your crops, because the fungus can live for long periods in the soil and even live among weeds such as ragweed. Choosing wilt-resistant varieties to plant is the best way to prevent Verticillium wilt.

15. Viral Diseases

  • What they looks like: Viral diseases mainly attack the tomatoes themselves. You might find black spots on tomatoes, or weird stripes on them. Don’t confuse signs of disease for just how some heirloom tomatoes look with natural stripes.
  • What causes them: Many of these viruses spread when plants are stressed by heat, drought or poor soil.
  • What to do about them: If you’ve read through all of these tomato problems and think your tomatoes may be suffering from a viral disease, spray your tomato plants with neem oil. Good soil management and using organic fertilizer for tomatoes helps keep your plants healthy, which can help them naturally resist viruses better.

16. Powdery Mildew on Tomatoes

  • What it looks like: Powdery mildew is easy to find on tomato plants as it looks like someone brushed the leaves with a white powder. You might find white spots on tomato leaves or even the stem. If you let the fungi thrive it will turn your tomato leaves yellow and then brown.
  • What causes it: Powdery mildew on tomatoes is more common in greenhouses than an outdoor garden because of the lack of air flow and high humidity.
  • What to do about it: The best way to prevent powdery mildew on tomato plants is to use a preventative spray formulated with sulfur. For more information, read this post on prevention and treatment of powdery mildew on plants.

5 Insects That Can Destroy Your Tomatoes

In addition to diseases, insects can damage tomato plants, too. Not all bugs are bad — some insects are extremely helpful, and some will even attack the “bad” bugs plaguing your tomato plants.

Be sure to browse the extended information on tomato plant pests below, but, overall, here are your best options for fighting insect infestations on tomato plants:

  • Caterpillar Killer with B.t. (Solution: Fight hornworms and other plant-eating caterpillars with this OMRI Listed® biological control that targets destructive larvae.)
  • Insect Killing Spray for Tomatoes. (Solution: An insect-killing formula for use on tomatoes that’s compliant for use with organic gardening and fights tomato hornworm, Colorado potato beetles, whiteflies and other caterpillars.)
  • Insecticidal Soap. (Solution: An OMRI Listed® insecticide soap that can be used up to the day of harvest on aphids, mealybugs, spider mites and other pests.)
  • Insecticidal Soap with Pyrethrin. (Solution: By mixing the features of insecticidal soap and pyrethrin, you can maintain your organic garden and fight spider mites, hornworms and destructive beetles.)
  • Neem Oil. (Solution: Neem oil kills insects in every life stage — from eggs to adults.)
  • Insect Traps. (Solution: Lure pest insects away from your plants and trap them before they can do more damage.)

The following tend to be the most common causes of various tomato pest problems.

1. Cutworms

  • What they are: Cutworms feed at night on seedlings. They “cut” or eat through the stem at soil level or an inch or less above the soil. Cutworms aren’t exactly worms — they are the larvae of certain moths. They only emerge at night and can be difficult to spot. Cutworms kill tomato plants by snipping them right in half.
  • What to do about them: Prevent cutworm damage by making a paper collar that fits around your seedlings. Just take newspaper or cardboard and fold it into an inch-wide strip. Use tape to make a collar around the plant, leaving about two to three inches around the stem. Remove the collar once the plant has several sets of leaves. You can also cut the bottom off of a paper cup and slide the open-bottom cup over the seedling to prevent cutworm damage.

2. Hornworms

  • What they are: Tomato or tobacco hornworms can decimate mature tomato plants in one night. These crafty insects are large green worms about two to three inches long with tiny horns on their head and ridged bodies. Hornworms are perfectly camouflaged so they look exactly like a tomato stem or branch, making them difficult to spot. They emerge at night, eat all the leaves off the plant and move on to the next section or plant.
  • What to do about them: Nature provides the best control for tomato hornworm in the form of a parasitic wasp that lays her eggs on the body of the hornworm. As the wasp’s larvae hatch, they eat into the living worm and eventually kill it. Natural methods to control tomato hornworms include planting marigolds around tomatoes. The strong marigold scent repels them naturally. Safer® Brand Caterpillar Killer II With B.T. uses a naturally occurring fungus to quell hornworms without harming earthworms. You can also use an insect-killing spray.

3. Colorado Potato Beetle

  • What they are: Colorado potato beetles are native to the United States. They love plants in the nightshade family, especially potatoes. If they can’t find potatoes, however, they will gravitate towards tomatoes, eggplant and other nightshade family vegetables. The beetles are about the size of dimes, with yellow-and-black striped wings. The adults use their mouthparts to chew holes in the leaves of tomato plants. Females lay clusters of bright gold or yellow eggs underneath the leaves. When the larvae hatch, they spread out among the tomato leaves, easily eating their way through the entire plant. Larvae are red to dark pink with black spots and frequently hide under the leaves during the day.
  • What to do about them: Use a pesticide with pyrethrins to spray on your tomato plants. This method works best in early spring before the larvae mature.

4. Stink Bugs

  • What they are: The brown marmorated stink bug isn’t only an annoyance inside the home. These insects also use their needle-like mouthparts to suck the juice right out of your tomatoes. They can be spotted with the naked eye on your tomatoes, or you can see their damage in the yellow, uneven spots that appear on the ripening tomatoes. When you slice into a yellow-spotted tomato, white sections appear under the yellow spots, which distinguish stink bug damage from fungal or viral problems.
  • What to do about them: Safer® Brand makes stink bug traps that harmlessly attract the insects to the trap and away from your tomatoes.

5. Spider Mites

  • What they are: Spider mites are difficult to see because they’re so tiny, but you can clearly see the damage they leave behind. Mites scuttle along the stems and leaves, piercing the leaves to feed on the juices. Eventually, tomato leaves look stippled and bronzed, with damage to the plant’s leaf structure.
  • What to do about them: The best method for treating spider mites on tomato plants is to use a neem oil spray. Another option is insecticidal soap, which also offers a treatment for spider mites.

Not Just Bugs: Bird Problems

One final tomato problem is often mistaken for insect damage: birds. Some birds, especially crows, love to eat ripening fruit, and tomatoes are technically a fruit. Crows peck with their large, sharp beaks at the ripening tomatoes, ripping open gashes and eating partial segments from various fruits. Other birds and even squirrels may also be at work if you find tomatoes that look like they have bites taken out of them.

The best control for bird problems is a net. A large fruit tree net, available at your local home or garden store, can be draped over the plants. The net is an effective deterrent to birds and usually a good deterrent for squirrels, too.

Although this list of tomato problems is extensive, don’t let it deter you from growing great tomatoes. The good news is that most of these diseases and problems still leave you with some edible tomatoes. And once you take precautions to avoid these diseases and pests in your future gardens, your tomatoes will continue to be fruitful and successful.

Tell Us About Your Tomato Problems

Join the Safer® Brand Community on Facebook, where we want to see the pictures of your tomato and garden problems. When you upload a photo or ask us a gardening question, we’ll get on the case and offer suggestions for your next steps.

Also, be sure to subscribe to the Safer® Brand E-Newsletter — signing up gives you links to helpful articles like this one.

  • Blight: Two fungal diseases are known as blight: Alternaria solani or early blight, and Phytophthora infestans or late blight. Early blight begins earlier in the season and creates target-shaped ring spots on the leaves, usually on the lower portion of the plant first. Late blight causes irregular blotchy spots on the leaves and fruit. Controlling the environment to prevent excessive heat, moisture, and crowding helps to inhibit fungal growth. Remove affected leaves and adjust care as necessary.
  • Leaf Spots: You’ll notice leaf spots in the center of leaves, a black or gray spot with a light center. Once the spots settle in, the leaf will turn yellow, then brown, and wither away. Leaf spots are caused by a fungus, encouraged by excess heat and moisture, so removing the affected leaves and adjusting the environment will help to stop the spread.
  • Bacterial Infection: Exposed to the plant through a cut or damage in the vine or plant, bacterial diseases can wreak havoc on your tomato plants. If your plants are experiencing bacterial infection, you’ll notice spots and blotches. To treat the problem, remove the infected areas as soon as you see them.
  • Mosaic Viruses: Because tomatoes are in the same plant family as tobacco (nightshades), tobacco users can transmit a mosaic virus to their tomato plants simply by touching them. While mosaic viruses won’t kill your plant, they will weaken them and reduce your crop, which is almost as bad. You can spot a mosaic virus by the mottled coloring on the leaves or fruit, with raised almost blister-like spots. Don’t allow smoking near your garden, and wash your hands or glove them before tending tomatoes if you are a smoker.
  • Verticulum Wilt: Sneaky and devastating, tomato wilt begins with sad, wilted looking leaves in the heat of the day that perk up later on, but then progresses to complete wilting and loss of the plant. It is caused by fungi that contaminate the root of the plant and block water and nutrients. There is no way to treat it, so when a plant dies from verticulum wilt, remove it completely and destroy it.

Diagnosing and Controlling Fungal Diseases of Tomato in the Home Garden

Soil-borne fungal diseases can be a major problem of tomatoes. There are three steps to understanding and managing tomato diseases in the home garden. The first step is to understand the disease cycle of a typical fungus. The second is to recognize symptoms of important fungal diseases of tomato, and the third is to apply good cultural practices to help minimize the damage caused by these diseases.

Simply, fungi live and obtain their nourishment from infected host tissue. Fungi reproduce by spores, tiny microscopic bodies, which are spread by wind, water, or other mechanical means to a new host. On the host, spores germinate and infect healthy plant tissue causing symptoms including leaf spots, rots, and wilts that lead to premature defoliation and reduced tomato yields. Development and spread of fungi in the home garden is determined by rainfall, relative humidity, free moisture, and temperature.

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Figure 1. Anthracnose fruit rot on ripe tomato fruit

Some of the most common fungal diseases that infect tomatoes grown in the home garden include Anthracnose fruit rot, Early blight, Septoria leaf spot, Late blight, and Buckeye rot all which produce distinct symptoms making them easily diagnosable by the home gardener.

Anthracnose Fruit Rot

Anthracnose fruit rot is a soil-borne disease that affects ripe tomato fruit. Infections go unnoticed on green fruit and as fruit ripens depressed circular water-soaked spots appear on red fruit. These spots may slowly enlarge to about 1/4-inch in diameter and produce black fungal structures (microsclerotia) in the center of the lesion just below the skin surface. Microsclerotia can overwinter in the soil and serve as a source of inoculum for the next growing season.

Early Blight

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Figure 3. Early blight causing rot on petal end of infected tomato fruit.

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Figure 2. Early blight lesion on infected tomato leaf with distinct concentric rings.

Early blight can infect tomato foliage and fruit. On tomato foliage, Early blight first appears as circular irregular black or brown spots on the older leaves of the plant. As these lesions enlarge a series of dark concentric rings develop in the center of the spot creating a distinct target pattern. Over time the tissue surrounding the early blight lesions can yellow and cause the leaves to drop. Severe infestations of this disease can cause 100% defoliation of the plant.

Early blight can infect the fruit through the calyx or stem attachment in the immature green or red stage and can produce distinct target-like lesions similar to foliar infection. Defoliation caused by early blight can reduce fruit yield and can leave the fruit open to sunscald injury.

Septoria Leaf Spot

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Figure 5. Septoria leaf spot lesion: Notice black fruiting bodies in center of lesion.

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Figure 4. Symptoms of Septoria leaf spot on infected tomato leaf.

Septoria leaf spot is a soil-borne fungal disease that only infects tomato leaves and stems. The spots enlarge to 1/8-inch in diameter and are distinguished by a dark brown edge with a white or gray center. As the disease develops and more leaf spots develop, the areas surrounding spots will turn yellow causing leaves to wither and die. The disease spreads from the older leaves upward and can totally defoliate a plant in a short period of time. Defoliation can severely inhibit yield and lead to sunscald injury and fruit cracking. If tomato plants become infected with Septoria leaf spot early in the growing season, plants can become 100% defoliated before fruit set.

Late Blight

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Figure 7. Late blight on mature green tomato fruit.

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Figure 6. Sporulating Late blight lesion on underside of tomato leaf.

Late blight is the disease historically associated with potatoes and the Irish potato famine of the mid-1800’s. The Late blight fungus can also infect tomato plantings. The disease will first appear as greasygrayish indefinite patches on older leaves and stems. These spots enlarge in moist weather and may produce white fuzzy growth on the underside of infected leaves. The fungus will also attack fruit causing a dark, greasy colored lesion with a slightly sunken, rough surface on green fruit. These lesions may enlarge turning the whole fruit brownish-black. Infected fruit often remain firm. Severe infestations can cause the foliage to brown and shrivel.

Buckeye Rot

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Figure 9. Sporulation of Buckeye rot on infected mature green tomato fruit.

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Figure 8. Buckeye rot of tomato with distinct concentric rings on mature green infected fruit.

Buckeye rot typically affects immature and mature green fruit that lay on the soil surface. On green fruit, buckeye rot will produce distinct brownish-black lesions that have a definite concentric or target-like appearance. In moist conditions, white fluffy fungal growth will develop on infected fruit. Over time, infected fruit will become soft and mushy.

Control Measures for Fungal Diseases in the Home Garden

There are a number of cultural practices that can be used to help reduce tomato disease in the home garden. The first cultural practice is to remove old plant debris. Fungal spores can overwinter in infected plant debris and on weeds related to tomato, such as horse nettle, ground cherry, and night shade. During the next growing season overwintering fungal spores are splashed from infested tomato or weed debris in the soil on to newly planted tomatoes restarting the disease cycle.

Proper sanitation measures can keep spores from infecting the next crop. At the end of the growing season all tomato refuse should be removed and discarded, composted (if the pile is hot enough to kill the spores) or tilled into the soil. Thoroughly burying the residue will keep the spores below the soil surface and away from tomatoes.

Crop rotation is another means to help reduce disease in tomato plantings. Each year plant tomatoes in a new location away from areas where tomatoes, eggplant, potatoes or peppers have grown in the past. These vegetables all have similar disease problems. A minimum rotation of three years is considered essential to help reduce populations of soil-borne fungi.

A second line of defense against leaf spot diseases is to alter the microclimate surrounding tomato plants. Fungi thrive in moist, humid conditions, in particularly on leaves that remain wet for long periods of time. Tomatoes should be grown in full sun with good air circulation to dry the leaves. Staking or caging tomatoes brings the plants up off the soil and allows more rapid drying of the plant.

Watering should be performed in the morning to allow sufficient drying time. The use of a soaker hose to irrigate completely eliminates regular wetting of the leaves.

Cover crop mulches such as composted leaves or straw mulch can be placed on the soil surface to help reduce soil-borne fungal diseases such as Buckeye rot and Anthracnose fruit rot by keeping developing fruit from coming into direct contact with the soil surface. The soil beneath and surrounding the tomato plant should be covered with at least 6 inches of mulch early in the tomato season. Mulching tomato plantings this way may also reduce weeds and prevent loss of soil moisture during the growing season.

Preventative fungicides can also be used to control fungal diseases in the home garden. Always read and follow directions on the label.

April 2005

Copyright © 2020 Rutgers, The State University of New Jersey. All rights reserved.

For more information: njaes.rutgers.edu.

Cooperating Agencies: Rutgers, The State University of New Jersey, U.S. Department of Agriculture, and County Boards of Chosen Freeholders. Rutgers Cooperative Extension, a unit of the Rutgers New Jersey Agricultural Experiment Station, is an equal opportunity program provider and employer.

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for Tomato Pests

Home-grown tomatoes are a source of pride, a thing of beauty, and beyond-description delicious. Whether heirlooms of the sort our grandmothers knew or a tried and true northern variety that gives us success despite June and September frosts, a perfect tomato is an achievement. If that perfect tomato is organic, kept pest and disease free without the use of harmful chemicals, it’s priceless.

To produce that perfect tomato, be alert. Keep an eye on your plant’s health, look for larvae and other insects, watch for signs of disease. And if you find them, come here for advice on what to do. Remember: part of a quick reaction is having the most efficient tools, products, and methods ready for when trouble shows its head. Be prepared.

The first task when facing an unhappy tomato plant is to diagnose the problem. Websites with pictures can be enormously helpful here. One of the best is Texas A&M’s Tomato Disorders page, which presents photographs under five headings, green fruit, ripe fruit, stems, leaves, and roots. What you can’t do on that site, though, is type in a suspected issue and call up an associated picture. One of the best sites comes out of Maine titled Common Tomato Problems: Diseases and Disorders.

Garden Pests

If you see an insect on or near your beloved tomato plants, don’t rush for the nearest insecticide. Many insects are beneficial to the garden or at least neutral. That insect may be feeding on the very pests you’re having trouble with. Even if you’re looking at an enemy, one insect does not make an infestation. It’s best to identify the intruder and the level of damage it’s causing before implementing steps in managing insect pests in vegetable gardens (hat tip to Cornell University).

Aphids
These are those dense clusters of tiny insects you may see on the stems or new growth of your tomato plants. While small numbers are not a big deal — don’t be afraid to crush them with your thumb — large infestations can gradually injure or even kill plants. Pinch off foliage where aphids are densely concentrated, and throw these discarded bits into the garbage, not on the ground. If the problem then seems manageable, release beneficial insects such as ladybugs or lacewings. If it doesn’t, go for the insecticidal soap that uses natural fats and plant oils (Organic Material Review Institute listed) or natural sprays, many of which are listed for organic production.

Cutworms
These are the tiny grub-like caterpillars that feed on young plant stems at night, frequently felling seedlings by eating right through them at ground level. Prevent damage by placing collars around seedlings. You can make these of paper, cardboard, aluminum foil, or an aluminum pie plate about ten inches long and four high, bent to form a circle or cylinder and stapled. Sink the collars about an inch into soil around individual seedlings, letting three inches show above the ground to deter high-climbers.

Flea Beetles
A potentially devastating visitor, the flea beetle (so-named because it resembles and jumps like a flea) attacks from both sides: adults eat foliage, leaving numerous small holes, while larvae feed on roots. They’re not picky, these beetles; they’ll go for corn, cabbage, lettuce, and all members of the Solanaceae family: peppers, eggplant, potatoes, and tomatoes. Unless levels are very high, damage can be minimized and controlled by using preventative measures.

  • Clear away or plow under weeds and debris, in which adults over-winter.
  • Place yellow sticky-traps to monitor levels and capture adults.
  • Use row covers. Young plants are more vulnerable to damage, so cover them to keep beetles off.
  • Dusting plants with diatomaceous earth (a chalky stone composed of marine fossils, ground to powder) helps control adults feeding on foliage.
  • To attack the insect more directly, introduce beneficial nematodes into your soil to feed on the larvae and pupae.
  • In cases of high infestation and serious damage, botanical insecticides such as pyrethrin can be used.

Hornworms
These destructive caterpillars are so big — three inches long or more — that it would seem to be easy to control them just by picking them off. And so it is, sometimes. The dilemma is that their pale green color provides excellent camouflage, and the nymph and larval stages are far smaller and less obvious. If there are only a few, picking them off works well. (One site suggests spraying the plant with water, causing the caterpillars to, and I quote, “thrash around,” giving themselves away.) If there are more than a few, other measures may be called for. One of these is Bt, or Bacillus thuringiensis, an organic treatment that can control numerous other caterpillars as well.

Nematodes
This is one of the most dreaded tomato problems. Actually, almost 20,000 different species of nematode have been identified, and billions of these usually microscopic worms occupy each acre of fertile earth, so it is fortunate that only a few cause gardening troubles. Some, insect pathogenic nematodes, can actually help control other gardening pests such as fungus gnats or flea beetles. But when a gardening friend says in a voice of doom, “I’ve got nematodes,” he generally means one thing: root-knot nematodes. This particular species invades various crops, causing bumps or galls that interfere with the plant’s ability to take up nutrients and to perform photosynthesis. They’re most common in warmer areas with short winters. Unfortunately, controlling nematodes is not easy.

  • Rotation: Since they take several seasons to get established, rotating garden crops denies this pest the chance to get entrenched. It’s crucial, though, that you follow tomatoes with crops that are not vulnerable to the same problem! Members of the same family are of course taboo; this includes peppers, eggplant, and potatoes. However, less likely crops are also vulnerable; these include okra and cotton, in the south, and peas, squash, beets, and numerous others anywhere. If you suspect nematodes — if you ever pull a plant that has odd-looking lumpy growths on its roots — have your county extension agent take a look at it, and get advice about crop rotation in your area.
  • Soil sterilization: Completely sterilizing the soil is one option on small plots, but it’s toxic and sometimes expensive. It also means that you’ve killed off all the beneficial organisms in the soil as well as the troublesome ones, so it’s particularly important to follow such treatment with a big infusion of clean compost. It would also be best to add earthworms, and an assortment of microorganisms as well, since doing so will restore the soil to full health and make it less vulnerable to further incursions by nematodes.
  • Nematodes: While eliminating nematodes is extremely difficult, it is possible to limit their damage by using resistant varieties, marked N. Doing so doesn’t kill the pests, but it does keep them and their effects under control.

Whiteflies
These tiny flying insects feed on plant juices, leaving behind a sticky residue or ‘honeydew,’ which can become a host for sooty mold. Rustle the leaves of infested plants, and clouds of these insects will rise. If you have a serious problem, you may be tempted to reach for a conventional insecticide, but don’t bother, as whiteflies have developed resistance to many.

  • The best bet is a horticultural oil, which effectively smothers all stages of this insect.
  • To deal with lower levels, place yellow sticky traps to monitor and suppress infestations.
  • Hosing down plants can be surprisingly effective, especially if you use a bug-blaster, a hose attachment designed to produce an intense multi-directional spray that easily reaches the undersides of leaves.
  • Another tactic is to release natural predators such as ladybugs, lacewings, or whitefly parasites.
  • If the situation is out of control, insecticidal soaps and botanical insecticides can bring populations down to manageable levels, at which point natural predators can maintain them.

Plant Diseases

Tomatoes can be stricken by an astonishing array of diseases. If you want to see the full list, go to the How to Manage Tomato Pests page at UC Davis, which discusses some 30 diseases that can afflict tomatoes. Tomatoes can get early or late blight, either white or grey mold (or both). Then they can have problems with diseases with quirky names like curly top and corky root rot. It’s amazing that tomatoes are ever healthy. But they are, and it’s largely because the quandary never gets thoroughly established. After all, it’s a lot less work to nip troubles in the proverbial bud.

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Approved for organic gardening. Bonide® Liquid Copper Fungicide controls a large variety of plant diseases including leaf curl, powdery mildew, black spot, rust, anthracnose and bacterial leaf spot. Use up to the day of harvest.

Avoiding Problems

If you’re at all susceptible to anxiety attacks, it will probably be of some comfort to know that disease is generally far less of an issue for backyard gardeners than for commercial producers. Furthermore, there’s a lot a gardener can do to minimize diseases in vegetable gardens (PDF).

Here’s how you can protect your tomatoes:

  • Give your plants good soil & fertilizer and regular watering; healthy plants are much more likely to resist diseases and other problems.
  • Keep gardening plots free of weeds and debris where insects can breed and diseases can incubate.
  • Rotate crops so that soil-borne pathogens never have more than a season to get established.
  • Clean your gardening tools and equipment, especially at the end of the season, to ensure that they don’t carry over or spread a disease.https://www.planetnatural.com/tomato-gardening-guru/pests-disease/
  • Remove unhealthy foliage; pull unhealthy plants to cut down on the spread of fungal spores.
  • Don’t compost diseased foliage or plants unless you know it is safe to do so.
  • Don’t use tobacco near tomato plants, to avoid communicating tobacco mosaic virus.
  • Avoid watering the foliage of your plants, especially in humid climates, as many diseases are encouraged by damp conditions.

The last on that list may be one of the most important. Many plant diseases — verticillium and fusarium wilt, early and late blight, and various leaf spots — are all caused by fungi that prefer damp, cool conditions. Experts generally advise gardeners to water in the morning in part to avoid conditions that encourage fungal growth or molds. Using drip watering systems or soaker hoses keeps leaves dry, again reducing attractive sites for the fungus to get established. Though some of these fungi are airborne, many reside in the soil or in garden debris or weeds related to the tomato. It is important, therefore, to keep weeds and brush piles clear of garden plots. It also helps to keep tomato foliage off the ground and to avoid splashing water up from the ground onto foliage while watering. Mulches help achieve both these objectives.

Damping Off
Caused by any of several viruses, damping off disease is a tomato problem that affects young, seemingly healthy seedlings that suddenly develop a dark lesion at the soil line, then quickly wilt and die. Cool, damp soil, overwatering, and overcrowding all increase probability of infection. Use clean potting soil and germination trays and tools to reduce incidence, avoid crowded seed beds, and monitor watering carefully during the first two weeks after sprouting.

Fusarium Wilt
Caused by a soil-borne fungus that targets Solanaceous plants (tomato, pepper, potato, eggplant), fusarium wilt often causes no symptoms until plants are mature and green fruit begins to reach its full size. At that point foliage, sometimes on only one side of the plant, turns yellow, and a sliced stem will show brownish, discolored tissue. Control includes crop rotation, so that the wilt organisms, deprived of a host, will die down in affected soils where it winters. Since cool, damp conditions favor infection, avoid spraying leaves, especially in cool weather. Use resistant varieties.

Mosaic Virus
There are actually several closely related viruses (the tobamoviruses) that cause the wilted, mottled, and underdeveloped fern-like leaves characteristic of the tobacco mosaic virus. All are spread by what are termed mechanical means: something or something that’s been in contact with the virus touches an uninfected plant, and voila — you’ve got an infected plant. Sanitation is therefore of the utmost importance, starting with never smoking near tomato plants, as tobacco can carry the virus. Infected plants should be destroyed. Backyard plants purchased from a reliable nursery or grown from certified disease-free seed and handled in a tobacco-free environment by only one or two people, are unlikely to develop this disease.

Verticillium Wilt
Like fusarium, verticillium is caused by a fungus that, once established in soil, is virtually impossible to remove. Symptoms are almost identical to those caused by fusarium wilt, but are less lethal. The edges of large, older leaves turn yellow, then brown and crumbly, and stems show vascular damage. Unlike fusarium, verticillium wilt affects a wide variety of crops, but lowers yield without killing plants. Again, avoid spreading infected soil and watering foliage, and again, use resistant varieties.

Environmental Conditions

Blossom End Rot
If your ripening fruits develop a dark spot at the lower end, a spot that gradually widens and deepens, you’re looking at blossom-end rot. It’s an environmental problem most often caused by uneven watering or by calcium deficiency. (These can be related; uneven watering can interfere with the uptake of calcium.) The simplest treatment is therefore pre-treatment: make sure soil is rich in all necessary nutrients, including liquid calcium, and water regularly. Mulches also help maintain even moisture levels.

Catfacing
Cat faced tomato plants are deformed to a greater or lesser extent, having deep grooves or indentations running from the blossom end all the way around to the stem. The condition results from cool weather or insect damage while the plant is in blossom. Tomato varieties with large fruit are most susceptible and tomatoes are often rendered inedible — although considered safe to it. To avoid the problem select resistant varieties whenever possible.

Cracking
Several things can cause cracking in tomatoes. Cherry tomatoes, especially small ones, frequently split at the stem end, sometimes all the way to the blossom end, and it does not indicate any sort of disease or problem. The skin of a tomato becomes less resilient as it matures, so the fruit often outgrows the skin. Pick cherry tomatoes just before full ripeness to avoid this.

Circular splitting at the stem end, (concentric cracking) or cracks running towards the stem (radial cracking) usually result from a sudden increase in moisture after a dry spell. Once again, the tomato fruit expands beyond the skin’s ability to adapt. Keep soil evenly moist to avoid this phenomenon.

Sun Scald
The tomato’s skin will look bruised or leathery, the skin sunken and puckered. It is essentially what it sounds like, a sun-burn, tomato style, and it occurs when fruit is too exposed during hot weather. This issue primarily affects staked and trellised tomatoes, which are more aggressively pruned than are caged or free tomatoes. To prevent this problem, be sure to leave adequate foliage on plants when pruning. Reusable shade cloth can also be used to protect tender vegetable plants. Once sunscald has occurred, you cannot do anything for affected fruit, but you can provide shade for the unaffected ones.

10 Tomato Plant Diseases to Watch For

From containers to expansive garden plots, growing tomatoes is a popular and relatively easy way to harvest at least some of your own produce. In fact, tasty and easy-to-grow tomatoes are the most popular garden vegetable. However, tomato pests and diseases such as tomato wilt can harm your crop. Don’t let those potential problems scare you away. Growing healthy, pest- and disease-free tomato plants is relatively simple. Keep your plants healthy by rotating crops, planting disease-resistant varieties, spacing plants properly, mulching, and watering at least 1 inch per week.

As tomato plants grow, keep an eye out for tomato pests and tomato plant diseases such as tomato wilt that may come in the form of fungi, bacteria, or viruses. In the fall, if you have had tomato plant disease problems or tomato pests of any kind, remove the entire plant. Rotate tomatoes so they grow in the same ground only every four years or so. Many tomato plant diseases and tomato pests lurk in the soil.

Related: Guide to Starting Tomatoes

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Septoria leaf spot is one of the most common tomato plant leaf diseases. You can first detect this fungus as it creates a small, circular spot with a grayish-white center and dark edges. Small black spots may show up in the center. Affected tomato plant leaves turn yellow, wither, and fall off. Long periods of warm, wet weather contribute to this tomato plant disease, and splashing water spreads spores to other leaves.

Control leaf spot by not crowding your tomatoes. Leave enough space so air circulates and dries leaves. Avoid overhead watering. When watering tomatoes, water at the base of the plant. Also, water in the morning so wet leaves have time to dry before evening. A fungicide formulated for tomatoes can be used to treat affected plants.

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Anthracnose

Follow the same procedures used for septoria leaf spot against the tomato plant disease anthracnose. This fungus shows up as a small, circular, indented area on tomato fruits. Eventually, rings surround the original spot. The flesh of the fruits may rot completely through, especially on overripe tomatoes, so keep fruits picked as they ripen. Spores are spread by rain splash, and the fungus is most common in warm, wet weather.

Related: Heirloom Tomato Varieties

Fusarium and Verticillium Wilt

These tomato plant wilt diseases are caused by fungi in the soil that enters through young roots, then begin to plug the vessels that move water to the roots and stems of the plants. Without water, the plants begin to suffer from tomato wilt on sunny days, although they appear to recover at night. Tomato wilting may first appear in the top or lower leaves of the plant, causing them to lose color, then die back from the tips. The process of tomato wilt continues until the entire plant is affected.

Heirloom tomato varieties that have not been bred to withstand these diseases are commonly attacked by tomato wilt. New strains of this tomato plant disease attack cultivars that are resistant to only one type of tomato wilt. Fusarium wilt is most common as a tomato plant disease in warm-weather regions and occurs during the warmest weather in cool areas.

To avoid these tomato plant diseases, plant tomatoes bred for disease resistance. They should be labeled V (for verticillium), F, FF, or FFF (for fusarium variations). Avoid overwatering tomato plants; just because a plant is wilted doesn’t mean it needs more water. Check the soil; if the soil is dry, then water the plant.

If your tomatoes are affected by one of these tomato wilts, remove and destroy all affected plants. Do not place them in your compost pile. Avoid using this location for tomato, eggplant, potato, and pepper plants for four to six years, because the fungi that cause the tomato wilt remain in the soil. Corn and beans won’t be affected. Keep weeds out of affected areas because their roots can continue feeding these pathogens.

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Early Blight (Alternaria)

Another tomato plant disease fungus, Alternaria, also causes leaf spot or early blight. Lower leaves show brown or black spots with dark edges, almost like a target. Stem ends of fruits may be attacked, showing large, sunken black areas with concentric rings. This tomato plant disease fungus usually strikes after plants set fruit.

The tomato plant disease late blight, caused by the fungus Phytophthora infestans, occurs during periods of cool, rainy weather that may come at the end of a growing season. It looks almost like frost damage on leaves, causing irregular green-black splotches. Fruits may have large, irregular-shaped brown blotches that quickly become rotten. This tomato plant disease fungus also affects potatoes and can be transferred from them. Use the same controls as for septoria leaf spot.

Mosaic Virus

Mosaic virus attacks many kinds of plants and is common in tomatoes. While mosaic virus doesn’t kill the plant, it diminishes the number and quality of fruits. The virus gets its name from the markings that resemble a mosaic of light green and yellow on the leaves and mottling on the fruits of affected plants. Leaves may also grow in misshapen forms, resembling ferns.

Because the virus must enter through a cut in the plant, avoid handling the plant. Anyone who uses tobacco can easily transmit the disease; wash hands thoroughly with soap to cut the risk of infection. Avoid this virus by planting resistant cultivars and not replanting in areas that previously hosted the problem.

Blossom Drop

Brought on by temperature extremes, blossom drop occurs when temperatures rise above 85 degrees F or drop below 58 degrees F. The temperature extremes cause tomato plants to discard their developing blossoms. Often, the damage is not realized until harvest is reduced later in the season.

Prevent blossom drop by using row covers to raise night temperatures. Little can be done to thwart high daytime temperatures. Maintain healthy plants so they will set new buds after the heat wave passes.

Related: Tips for Growing Healthy Tomatoes

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Blossom-End Rot

Caused by a lack of calcium, most often brought on by fluctuating water availability, blossom-end rot is a common tomato disorder. It appears as a sunken, dead area opposite the stem (the blossom-end of the fruit). The area will expand as the fruit matures.

Prevent blossom-end rot by promoting steady, stress-free plant growth. Water plants regularly to maintain moist, but not waterlogged, soil. Spread a 2-inch-thick layer of mulch around plants to conserve soil moisture.

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Damping Off

A frustrating fungal disease, damping off causes sudden collapse of seedlings, or failure to germinate. There are many steps you can take to prevent damping off. First, plant seeds when soil is at optimum temperature. Presoak seeds to speed germination. If planting seeds in potting mix, use sterile potting soil and containers. Allow the soil to dry between waterings.

Sunscald

Essentially a sunburn on a tomato, sunscald causes a section of the fruit to become soft, light in color, and dry. Prevent sunscald by maintaining enough foliage to shade fruits or shade fruits artificially with a shade cloth.

Related: Tips for Growing Heirloom Tomatoes

Tomato Bacterial Diseases

Tomatoes can fall prey to a number of tomato plant bacterial diseases, including bacterial spot, bacterial speck, and bacterial canker. They’re all slightly different but appear as spots on leaves and fruits. Use the same controls as for septoria leaf spot. Grow disease-resistant plants. Avoid rotating the same ground with peppers, which can host the same diseases. Avoid pruning and tying plants, because the bacteria can enter any openings made during these procedures. Fixed copper sprays may reduce the spread if applied as soon as symptoms begin.

Understand the Tomato Plant Disease Code

Disease resistance has been bred into many tomato varieties. The letters behind the names are codes showing what diseases and insects the tomato plants are bred to resist, including:

V Verticillium wilt
F Fusarium wilt
F Fusarium wilt races 1 and 2
FFF Fusarium wilt races 1, 2, and 3
N Nematodes
A Alternaria alternata (stem canker or early blight)
T Tobacco mosaic virus
St Stemphylium (gray leaf spot)
TSWV Tomato spotted wilt virus

For example, the label on Big Beef VFFNTA Hybrid, a winner of a 1994 All-America Selections award, tells you that it is bred to resist verticillium wilt, fusarium wilt races 1 and 2, nematodes, tobacco mosaic virus, and Alternaria, and early blight.

  • By Deb Wiley

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