These 10 common tomato plant problems can put a damper on your summer gardening.

The best way to prevent these common tomato plant problems is to learn what causes them and how to treat them if you find tomato plants with them.

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​Learn more about the 10 common tomato plant problems below.

Nothing tastes as good as a fresh, straight from the garden, homegrown tomato.  Unfortunately, there are some diseases and pests that will try to prevent your tomato plants from making that delicious fruit.

The following pests and diseases are the most common issues that tomato plants have.  These aren't the only things that can affect your tomato crop, but they are the most common.

​Generally, if you're having issues with your tomato plants, it's probably going to be one of these things.  I've put some links in at the bottom if you find that none of these sounds like what you're dealing with.

If you notice that your tomatoes develop dark, wet spots on the underside (blossom end), then you're dealing with blossom-end rot.

Blossom-end rot is most common when the early growing season is wet and then dry when the fruit sets.  Thankfully, blossom-end rot is usually limited to a few tomatoes on the plant.

​This condition affects more than just tomatoes.  Peppers, squash, cucumbers and melons can all get blossom-end rot.

Causes of Blossom End Rot

Blossom-end rot is not caused by a disease or pest.  It's a sign of a nutritional disorder in the plant.

Plants that develop blossom end rot have a calcium deficiency.

Preventing and Treating

One of the easiest ways to treat blossom-end rot is to prevent it by mending the soil properly.  Have your soil tested to see what nutrients need to be added.

Lime can be tilled into the soil 3-6 months before planting.  If that doesn't add enough calcium, gypsum can be added before planting.  Add 1-2 pounds per 100 sq. ft. and till it into the soil.  Gypsum will not raise the pH of the soil like lime will, which is important to plant health.

Eggshells can be crushed and placed around the plant.

Blossom-end rot foliar sprays containing calcium chloride can be sprayed directly onto the plant.  Spray the plant in the morning or late in the evening.  If you spray it on the plant in the middle of the day, it will burn the plant.

Avoid using fertilizers with excessive potassium or magnesium.  Calcium, potassium and magnesium all compete with each other to get taken up by the plant.  Epsom salt is a strong magnesium fertilizer and can prevent the plant from taking in enough calcium, leading to blossom-end rot.

Treat with:

-Agricultural Lime
-Gypsum
​-Foliar spray

Flowers need to stay on the plant during pollination in order for the fruit to set properly.  A tomato plant that is dropping flowers or not setting fruit properly is under some kind of stress.

Causes for Flowers Dropping and Fruit Not Setting

Usually, the source of stress is the temperature.

Flowers will drop if temperatures are above 90 degrees or below 50 degrees for extended periods of time.

Drought stress, excess nitrogen, and too little sun can also cause flower and fruit problems.

Preventing and Treating

You can't control the temperature but you can support the plant in other ways.

If you live in an area that frequently gets temperatures above 90 degrees, purchase heat-tolerant tomato varieties.  you can also purchase shade cloth to drape over the plants during periods of extreme heat.

Drought conditions can cause flower drop, so make sure that the soil doesn't get dry.

Tomato plants require lots of energy to produce tomatoes, and they get that energy from the sun.  Make sure that your tomato plants are getting at least 6 hours of sunlight per day.

Over-fertilizing your tomato plants with too much nitrogen can cause flowers to drop.  Nitrogen causes the plant to focus on growing leaves, not fruit and flowers.  If you've accidentally given your tomatoes too much nitrogen, you can fertilize with superphosphate or 0-20-20 fertilizer.

Treat with:

-Superphosphate
-0-20-20 Fertilizer
-Shade Cloth
​-Soaker Hose

One of the 10 common tomato plant problems is, unfortunately, blight.  There are two distinct types, early blight, and late blight.

Early blight shows up as dark, ringed spots on the lower leaves and stems.  If left unchecked, it will move up the plant and will kill it.

​The spots start off as brown spots that grow in size.  The spot itself resembles a bull's eye. The tissue around the spot will yellow.

Causes of Early Blight

Early blight is caused by two types of fungi: Alternaria tomatophila and Alternaria solani.  The fungi live on infected debris in the soil, on seeds, and volunteer tomato plants.

The fungi can also live on and infect potatoes.

Preventing and Treating

Blight-tolerant varieties of tomatoes are available.

Remove any infected leaves and stems and destroy them.  Do not compost them.

When watering tomatoes, keep water off of the leaves.  Water the plants at the ground to keep moisture off of the foliage.  Early blight spreads rapidly in warm, humid conditions.

When you're planting, space the tomatoes out far enough that they won't touch each other.  Stake the plants to encourage good air circulation.

Blight can live on weeds and volunteer tomato plants that live around your tomatoes.  Remove these when they come up so that they don't harbor the fungi.

You can treat early blight with fungicides that contain mancozeb, chlorothalonil, or copper fungicide.

Treat with:

-Soaker Hose
-Tomato Stakes
-Mancozeb Fungicide
-Chlorothalonil Fungicide
​-Copper Fungicide

Late blight attacks newer leaves.  The leaves and stems will develop areas that look like water-soaked lesions.  These lesions grow in size and white mold will develop around the edges of the affected areas.

Late blight can quickly overtake a plant.  Tomato plants can be completely defoliated within 14 days of seeing the first signs.

​Tomato fruits that become infected develop dark, shiny lesions.

Causes of Late Blight

The fungus Phytophthora infestans causes late blight.  The spores that cause late blight can be carried by rain and wind, making late blight very contagious.

You can visit the site USA Blight to monitor where late blight is in the United States currently.

​Late blight thrives in cool, wet conditions.  Typically, it is seen at the end of the growing season when temperatures are in the lower 70's and humidity is high.

Preventing and Treating

Keep the leaves of the plant dry. Water the plant at the ground, not from above to prevent getting the foliage wet.

Space plants out and stake them to encourage proper air circulation around and between plants.

Any dew that falls at night will collect on the leaves.  Tomato plants need ample morning sun to dry the moisture from their leaves.  Make sure that the tomato plants are getting at least 6 hours of sun a day and that they get plenty of morning sun.

Late blight can be treated with fungicides such as Actinovate or a copper fungicide.

Treat with:

-Tomato Stakes
-Actinovate
​-Copper Fungicide

Of the 10 common tomato plant problems, this is my personal least favorite.  Not that I like the rest of these issues, but I really dislike tomato hornworms.

Tomato hornworms are common tomato pests and will seemingly appear overnight.  You'll notice that some of the leaves are missing with the stems still intact.  You may also notice that some of the fruit is eaten.

Hornworms are the caterpillar of the sphinx moth.  They are green with yellow and white on the body.  They can be hard to detect because they are almost exactly the same color green of the tomato plant.

​The tomato hornworm usually produces one generation per year in the Northern U.S. and two generations per year in the Southern U.S.

Preventing and Treating

Sprays intended to keep pests off of your vegetable plants will keep tomato hornworms (mostly) at bay.

If you see that leaves are missing from a hornworm, don't rest until you find it.  They can make quick work of a tomato plant and will move from plant to plant.

This year, we started raising honeybees that visit the plants in our vegetable garden.  We've started using bee-friendly methods of getting rid of hornworms.

You can simply pull off the hornworms and submerge them into a bucket of soapy water to kill them.  You can also try bee-friendly pesticides.

Hornworms are in the larvae stage.  After they've eaten their fill, they will bury themselves in the soil below your tomato plants and cocoon themselves for the pupae stage. They will then emerge as adults from the soil, ready to start a new generation.

​Tilling your garden soil is really effective at killing hornworm pupae.  It's most effective if you till right after the growing season is finished.

The braconid wasp is a natural parasitic predator of the hornworm.  Adult wasps will lay eggs on the body of the tomato hornworm.  These eggs will hatch and the babies will eat the hornworm.

The eggs look like small white sacs on the back of a hornworm.  If you notice these, don't kill those hornworms.  Let the wasp do its thing and kill them for you.

Treat with:

-Bee-friendly Pesticides
-Garden Pesticide
​-Insect Killing Soap

Slugs will chew holes into the fruits of your tomato plants.  They won't chew all the way through it like a hornworm will.

You might notice small, circular holes in some of the fruits.

Preventing and Treating

Iron phosphate-based slug pellets are really effective at keeping slugs off of your tomatoes.

Beneficial nematodes are natural predators of slugs.  They will help to manage the slugs in your garden.

I haven't had issues with slugs in my garden, but I use black plastic mulch that deters many pest insects.  It is possible that the slugs don't like the plastic mulch.

Treat with:

-Iron Phosphate-based Slug Pellets
-​Plastic Mulch

Of the 10 common tomato plant problems, this one is probably the most annoying.  You'll be growing perfect, beautiful tomatoes and then all of a sudden, your tomatoes crack.

Not only will they crack, but the cracks will fill with ugly scar tissue that is brown.  In the right conditions, the open wound can harbor mold and bacteria that will cause rot.

​Cracks also invite birds and insects for an easy treat.

Causes of Cracks in Fruit

Cracks in tomatoes are most often caused by uneven watering.

Tomato plants that are dry become thirsty.  When you water these thirsty plants, they soak up too much water.  The excess water causes the tomato to burst, or crack.

Preventing and Treating

Many heirloom varieties are more susceptible to cracking.  Some tomato varieties are crack-tolerant and will crack less.

The easiest way to prevent this is to make sure that your tomatoes have sufficient water all of the time.  Plants that are well-hydrated will not gorge themselves when water is available.

Treat with:

​-Soaker Hose

Tomatoes that are lumpy, bumpy or have a puckered surface or odd shapes are considered catfaced.  Don't confuse these with some of the heirloom varieties that don't have the round and smooth shape of store-bought tomatoes.

These tomatoes are disfigured and may have scar tissue at the blossom end.

​Catfaced tomatoes are safe to eat.  If there is any scar tissue, simply cut it away.

Causes of Catfacing

Catfacing is most common when the temperatures are less than 55 degrees during fruit set.

​The cold causes the blossoms to fall off. If the flower is pollinating before the petals fall off, some stick to the developing tomato.  This is what causes the lumpy, distorted appearance.

Preventing and Treating

Unfortunately, you can't control the weather.

Plant tomatoes after temperatures have risen sufficiently.  You don't want plants in the garden when temperatures will drop below 55.  Tomatoes will drop flowers and any tomatoes that develop may be catfaced.

​The tomato variety Homestead 24 is resistant to catfacing.

When you see wilted leaves, you'll probably assume that your plant needs water.

And while this could be the case, monitor the plant after you water it.

Causes of Wilted Leaves

Tomatoes will become wilty if they need water.  Water creates pressure inside of the plant (called turgor pressure) that helps to hold the plant upright.

Not enough water and the plant droops.  When you water the plant, they should perk back up.  You should see a noticeable difference a couple of hours after watering.

If there isn't a difference, your tomato plant could have fusarium wilt.

Fusarium Wilt

Fusarium wilt is caused by the fungus Fusarium oxysporum.

The fungus lives in the soil around the roots of the tomato plant.  It enters the plant through wounds in the root system.

The fungus lives in the water-conducting vessels of the plant.  Eventually the fungus will block off the water-conducting vessels in the plant, preventing water from moving through the plant.  That's why it still appears wilty even after watering.

Another sign of fusarium wilt can be seen in the leaves.  The lower leaves will droop and become wilty. Leaves will lose their green color.

You may notice that leaves on one side of a stem turn golden yellow.

When you cut a stem of a tomato plant that has fusarium wilt, you'll see dark brown areas.  These are the infected water-conducting vessels.

Preventing and Treating

Make sure that your tomato plants are getting adequate water all of the time.  Aim for about an inch of water per week per plant to keep it hydrated.  If you notice a droopy plant, water it and monitor it closely.

There are varieties of tomatoes that are resistant to fusarium wilt.

Treat with:

​-Soaker Hose

Tomato plants will yellow, curled leaves could have two separate conditions.  They could be suffering from an aphid infestation or from tobacco mosaic virus.

Aphid Infestation

Aphids are small winged insects that are usually beneficial.  They can overcrowd on new growth and cause stress on the plant.

To check for an aphid infestation, check the undersides of the tomato leaves and on any new growth.  Aphids are small and white.

Preventing and Treating

Aphid infestations are easily controlled.  Spray them with a water hose to remove them.

You can also spray them with neem oil.

If you don't see any aphids, your plant likely has tobacco mosaic virus.

Treat with:

-Neem Oil
-Tobacco Mosaic Virus

Tobacco mosaic virus is most commonly seen in gardens of people who smoke.  The virus can be transmitted from the hands of the gardener to the plant.

The virus must enter through a wound on the plant.

Preventing and Treating

If you smoke, wash your hands thoroughly before going into your garden.  Don't smoke in the garden.

There is not a chemical control for tobacco mosaic virus.

It helps to rotate your crops in the garden.  Rotate tomatoes with cabbage, broccoli or turnips.

​There are some tobacco mosaic virus resistant varieties of tomatoes available.

You can help your tomato plants survive many of these conditions by making sure that they receive enough water, are in a good location, are fertilized properly and are planted at the right time.

Monitor your plants daily.  Many tomato plant problems show signs early and can be treated before the entire plant is lost.

​If your tomato plant is having problems that is not listed above, check out this article from Clemson about tomato diseases and disorders or this article from the Farmer's Almanac about common tomato plant problems.
​
​If you haven't yet, grab your FREE copy of the From Seed to Supper guide and learn how to start growing delicious, fresh vegetables and herbs!

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