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.

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.

Help for tomato plants

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.)

what does blossom end rot look like on tomatoes

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.

blossom drop on tomato plants

 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.

 why are my tomatoes cracking

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.

 

what does sunscald on tomatoes look like

 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.

 

Poor Fruit Set - Why are my tomatoes not growing

 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.

 

catfacing tomato

 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.

 

Why are my tomato plant leaves rolling and shriveling up

 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.

 

tomatoes look normal but gaps inside

 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.

 

tomato plant disease - bacterial canker

 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.

 

Anthracnose - dark mushy spot on tomatoes

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.

 

early blight on tomatoes

 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.

 

Tomato fungus - Septoria Leaf Spot

 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.

wilted tomato plant fungus

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.

Verticillium Wilt - Tomato plant fungus with yellow spots on leaves

 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.

What wrong with my tomatoes - spotted wilt virus

 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 also helps keep your plants healthy, which can help them naturally resist viruses better.

 

powdery mildew on tomato leaves

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.

Help for 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.

cutworms on tomatoes

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.

 

hornworm on tomato plants

 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.

 

Colorado potato beetle damaging tomato plants

 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.

how to get rid of stink bugs on tomato plants

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.

 

how to get rid of spidermites on 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. 

Source of Article: http://www.saferbrand.com.

Tomato Pests & Disease in Pakistan

A number of tomato troubles (insect, disease, environmental) can wreak havoc on your favorite plants. We identify them here and list earth-friendly solutions for controlling them.

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 problem and call up an associated picture. One of the best sites comes out of Maine titled Common Tomato 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 problem — 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 problem 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 problems 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 problems. 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 micro-organisms 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.

White flies

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 problems never get thoroughly established. After all, it’s a lot less work to nip problems in the proverbial bud.

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 back-yard gardeners than for commercial producers.

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.
  • Remove unhealthy foliage; pull unhealthy plants to cut down on the spread of problems.
  • 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. Back-yard 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
Catfaced 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 problem 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 sun scald has occurred, you cannot do anything for affected fruit, but you can provide shade for the unaffected ones.