What’s Wrong With My Tomatoes?

In our last vegetable installment, we talked about how to get started growing your own food at home. While a busy schedule (a very young, new child) prevented me from getting a blog out about getting started on spring vegetables, I’m sure many of you made your way to growing your own tomatoes at home. Growing spring veg is about the same as growing autumn veg, so I still hope to get that information out soon.

Growing tomatoes at home is one of the first and primary vegetables that people choose to start with. You use them on sandwiches, make pasta sauce, salsa, or just snack on them if you’re growing a cherry/grape variety. You can easily grow them in-ground, or in a pot on the back porch. Tomatoes can come with a host of problems, unfortunately. They’re not hard to grow if you follow certain basic steps, but issues may come up that are beyond your control. There are things you can do to take to prevent some of these problems, and we’ll talk about that in this edition.

Previously, I mentioned how every year can be different and present new problems and challenges. At my home garden this year, I’ve run into more animal issues than I ever have before. A strong thunderstorm came with rain and wind and knocked my sweet corn to the ground. Groundhogs and rabbits continuously broke into my weave fence and had their way with cabbage, lettuce, kale, bush beans, Swiss chard, and seemingly everything else I tried to grow. When I thought I had all the holes plugged, my pole beans were eaten 4 feet up from the ground, much too high for either of those critters. Deer, I presumed. Amidst all of this, occasionally I would see a tomato on the ground with a bite taken out of it. This is a sure sign of a groundhog. My solution will be to remove all the fencing and spend some money on a stronger fence that will be sunken into the ground on all sides. Maybe we’ll have a bit of fun next year and make a scarecrow while we’re at it. Despite all of this, I stayed vigilant and patched fence holes, tied up the corn, and was rewarded with a fairly decent harvest of tomatoes and corn. Those are my two favorite vegetables to grow anyway.

Healthy Gardeners Delight Tomatoes


Insect Problems

Before we discuss fungal problems and diseases, let’s further talk about issues that stem from animals and insects. It is possible you may find holes or chewed leaves on your plants. Take a closer look. You may find a hairless, green tomato/tobacco hornworm. This is a fat, green caterpillar with black and white markings along its body. Remove these if you find them by knocking them off with an instrument of your choosing into a container of soapy water and dispose of them. If you find one of these, it’s very possible you may see many white bumps sticking out of its body. These are the cocoons of wasp parasitoids, a natural enemy of the tomato hornworm. In this case, happily leave them be. They’ve most likely already killed the hornworm, and you want to keep the wasps in your garden. You can attract beneficial insects like these by having small flowers in your garden such as yarrow, cosmos, dill, fennel, and more.


Probable Flea Beetle Damage


Two other insect problems you may encounter are flea beetles and spider mites. Flea beetles leave small holes in the leaves, and may possibly be controlled by putting a garden mesh or netting over your plants from the time of planting until flowering. Spider mites are extremely tiny and will leave a speckled, mottled effect on the leaves. Insecticidal soap may be applied to control spider mites, but follow directions on the label and realize that if damage has already gotten bad enough that treatment may do more harm than good. Make sure that weeds in the garden area are suppressed, and that any fertilizer applied doesn’t contain an excessive amount of nitrogen that results in extra soft new growth. These things will encourage bad insects.


Environmental Problems

One of the best ways to prevent insect and disease problems is to grow strong, healthy plants. Follow practices such as growing in healthy, organic soil, mulching, and watering regularly. We’ll talk more about this in a moment, but tomatoes don’t like extremes in temperature or watering. Letting them dry out to the point of wilting, then soaking them (or teasing them with a smaller amount of water), and ignoring them until they are dry again is a great way to encourage unhealthy plants that will be easy pickings for insect and disease problems. Mulch generously, and keep plants evenly moist at all times. In addition to this, prune tomato leaves 12 inches from ground level so that no leaves are touching the soil and picking up any potential bad guys.

Speaking of extremes in temperature, some of you are very likely experiencing leaf curl right now. Our nights over the last 2-3 months have been strangely cold. Daytime temperatures are warm, and nights have reached the low 50s. If you’ve left your windows open at night and get up before sunrise like me, you’ll know what I mean. Colder than normal nights, especially mixed with irregular watering, can cause tomato leaves to curl up. There’s nothing you can do about the temperature, but if you get your watering schedule right, leaf curl should not hurt your fruit production.

Adventitious roots

Two very common problems that are related to this are blossom end rot and catfacing. Blossom end rot is just what it sounds like, a brown rotting spot on the end of a tomato fruit. It can also occur in peppers, eggplant, watermelon, and other vegetables and fruits. It’s caused by lack of calcium in cell walls, and gardeners often run to purchase special tomato food containing calcium to solve the problem. That might help, but the cause of this is usually a problem with uptake of available calcium in the soil caused by a poor watering schedule. There’s no way to know if your soil lacks calcium unless you do a soil test, which is a great idea anyway. It also doesn’t hurt to use a tomato food, whether it be a liquid feed or granular, but nutrients can’t be taken up properly if there’s not enough available moisture to do it.

Zippering and Sun Scald

Catfacing is caused by cooler temperatures at night. Fruits are misshapen, with crevices and holes forming around the underside. Varieties with larger fruits tend to be more prone to this. These fruits can be removed becasue they will not mature correctly. Make sure to place new plants out when there is no threat of frost and nighttime/soil temperatures are warm enough. In Pennsylvania, this is usually at the end of May or in early June.

Another thing you may notice are small bumpy nodules along the main stem of the tomato.  Tomatoes produce roots along their stems on non-root tissue. These are called adventitious roots. When you first put your tomato plant in the ground, it’s best to plant it deep, up to its first set of leaves. Roots will develop along the stem and form a stronger root system. These bumps are a good thing!

A thin line along the side of the tomato is called zippering and is only an aesthetic problem. This is caused by flower parts sticking to the side of the fruit as it develops.

The final environmental problem I’ll mention is when the sun beats down on a tomato because of removed leaves that would normally have shaded the fruit. I’ll often times remove leaves intentionally if a group of tomatoes is being shaded too much by a branch, causing the fruits to not ripen quickly enough. Sunscald is caused when when there is too much sun exposure on a fruit for too long a time. The area will be light and blistery, and the fruits will be largely inedible and should be removed.


Fungal and Bacterial Problems

Leaf Curl from cold nights.

The first fungal problem we’ll mention here is Early blight. This common tomato problem can occur on plants such as eggplant as well, and is usually brought about by rainy weather. Older, lower leaves get wet, and irregular brown spotting appears, surrounded by yellow halos. It can spread to other leaves and other plants, which is why spacing your individual tomato plants is important. I plant at least three feet apart. If the fungal infection is severe enough, it can kill your plants and ruin the fruits. The fungus may also overwinter in the soil. Clean up any debris from infected plants and do not allow it to lay on the ground over winter. I often prune out less than desirable foliage as I see it while I’m pruning suckers out of the plant, cleaning my cutting instrument between plants. Again, regular watering at the soil level (not watering foliage) and keeping leaves pruned off the ground can help prevent fungal issues from popping up. Early blight can act often appear at the same time as Septoria leaf spot. This fungus causes small grey spots and can lead to leaves yellowing and dying. It is also typically caused by wet weather.

Bacterial spot and bacterial speck are also caused by wet weather, or improper watering by tomato parents. If I haven’t said it enough already, don’t water tomato leaves. Bacterial spot can look similar to Septoria leaf spot, but the spots may become raised and appear scabbed over. In this instance, leaves may also yellow and die. Bacterial speck looks similar but the spots are smaller and more numerous. Bacterial diseases can be transmitted through seed, so it’s a good idea to buy your seed from a reputable source (if you’re starting your own at home).

Fusarium wilt is caused by a soil-borne fungus and can cause lower leaves to appear wilted and yellow. It may begin to spread throughout the plant. If you scrape the stem you will likely see browning of the tissue just under the very outer tissue of the plant. Fusarium does not spread from plant to plant above the ground. It can be brought into the garden with the introduction of infected plants or soil. Verticillium wilt will happen more slowly, but the effect tends to be seen on most of the plant all at once. Bacterial wilt will occur from the top of the plant and work toward the bottom.

Probable Start of Early Blight

Though not fungal or bacterial, I’ll include mosaic viruses in this section. Mosaic viruses can happen to a lot of different vegetables. Symptoms may include yellow mottled leaves, twisted or malformed foliage, or stunted growth. The symptoms are first observed on foliage, but can spread to fruit. Fruit may also appear spotted or mottled with greens and yellows. Viruses are typically spread by insects, but some may be transmitted through pruning instruments. There is not treatment for plants infected virally. They need to be pulled out, bagged, and disposed of by your waste collector.


This is Overwhelming and Scary.

After all of this information, please don’t be encouraged to quit gardening and buy your vegetables at the super market. There are a lot of problems that can happen to nearly any plant you grow. Some have more potential issues than others. Tomatoes and a few other vegetables have things you need to keep an eye out for. Fungal diseases can be treated with copper fungicides.

If you’re growing your tomatoes in pots, refresh the soil with new every year and clean your pots well. Old soil can either be added to the compost pile where internal heat will be enough to kill the baddies, or reused for things that don’t get the same diseases. You can mix in some fresh soil if you decide to reuse your old tomato soil for your zinnias next year. Home grown vegetables taste better than what you buy in the produce department. Real deal. I promise!


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