Typical Tomato Problems + What To Do About Them

Things looking wonky in your tomato patch? Learn to identify common tomato problems—and fix them.

Photo By: Julie Martens Forney

Photo By: Julie Martens Forney

Photo By: Julie Martens Forney

Photo By: Julie Martens Forney

Photo By: Julie Martens Forney

Photo By: Julie Martens Forney

Photo By: Julie Martens Forney

Photo By: Julie Martens Forney

Photo By: Julie Martens Forney

Photo By: Julie Martens Forney

Hungry Squirrels

Many critters have a taste for tomatoes, including squirrels and chipmunks. When these animals are the culprits behind tomato damage, you see something like this: a bite (or three) missing from a ripe tomato. Occasionally they nibble green tomatoes, but most often it’s the ripe ones they choose. If birds are eating your tomatoes, you’ll see more of a piercing, pecking-type wound that’s often triangular in shape. The best way to outsmart varmints is to protect ripening ‘maters. Either pick them slightly under-ripe and let them continue to ripen indoors, or cover plants or individual fruits with bird netting.

Bugs And Slugs

This tomato is a literal buffet for insects, including slugs, pillbugs and sowbugs. Heavy rainfall led to tomato cracking, and then bugs moved in to take advantage of the free food. To deter these insects, stake tomato plants so fruit is elevated and off the ground. Gather fallen fruit, removing it from the tomato growing area. Sprinkle diatomaceous earth or essential oil-infused natural bug killers, which typically have an inert base of materials like crushed limestone or peanut shells.

Blossom End Rot

When tomatoes develop a dark, sunken spot on the bottom, that’s known as blossom end rot. This condition occurs when plants don’t get enough calcium—either because there’s not enough in soil or soil pH is too low for plant roots to absorb calcium. Hot weather and uneven watering also contribute to the problem. The best way to beat blossom end rot is to do a soil test prior to planting, in spring. You might need to add lime or gypsum to increase calcium in soil. During the growing season, water tomato plants regularly and add a mulch layer to maintain soil moisture. Calcium-containing sprays applied to tomato leaves can also help boost calcium levels in the plant. When using calcium sprays, follow directions carefully.

Cracking

Tomatoes crack as a result of hot weather and heavy rain. Typically it occurs when summer thunderstorms soak dry soil, plants rapidly suck up the water, and ripening tomatoes enlarge so quickly that they burst their skins. The best defense against this issue is twofold. First, keep soil where you grow tomatoes moist with regular watering and mulching. Second, when heavy rain is forecast, harvest nearly ripe tomatoes. You can let them finish ripening indoors. Some tomato varieties are more prone to cracking, including most cherry tomatoes.

Sunscald

Hot summer sun can burn tomatoes, causing a condition known as sunscald. It’s not much different from a sunburn on your skin. Sunscald results in a white patch that has very thin skin. The flesh beneath doesn’t taste good. The problem occurs when there aren’t enough leaves to shade fruit. Staking tomatoes or using cages helps leaves to dangle and cover fruit. Use care when pruning tomato leaves. Make sure you don’t remove all the leaves that shade ripening tomatoes.

Tomato Hornworm

Keep an eye peeled for tomato hornworm, a worm with a voracious appetite. A mature hornworm can eat an entire tomato plant in one night. During the day, tomato hornworms hide beneath leaves, camouflaged beautifully. Often the only clue that these munchers are present is their frass (that’s science-speak for hornworm poo), which resembles black peppercorns. If you see eaten leaves or frass, inspect the plant carefully to find the hornworm and knock it into soapy water. If you spot a hornworm with white tic tac-looking items sticking out of its body, leave it alone. It’s been parasitized by a braconid wasp. When the wasp young emerge from the cocoons, they’ll eat the hornworm.

Anthracnose

Classic anthracnose symptoms include circular, water-soaked spots with a dark bull's-eye. A mold-like fungus eventually develops. Anthracnose is caused by a fungus that lives in soil. It’s more prevalent in poorly drained soil. Leaves or tomatoes that come into contact with soil can pick up the fungus spores. Rain and overhead irrigation can also splash fungus spores onto plants. To avoid this disease, improve poorly drained soil by adding organic matter. Stake plants to keep them off soil, and pick tomatoes before they become overly ripe, which makes them more susceptible to the disease.

Catfacing

When tomatoes are weirdly deformed, that’s known as catfacing. It usually happens on the bottom end of the tomato and results from cool temperatures (50 F to 55 F) during pollination. Usually when temps fall that low, tomato flowers drop from the plant. But if a blossom has been pollinated and the evening is unusually cool, the flower can get stuck on the newly forming tomato. The stuck-on bloom doesn’t allow the tomato to enlarge and form freely. This typically occurs on tomato plants that are tucked into soil too early in spring. It also happens in cool-weather regions when late summer evenings dip into chilly fall-like temps while plants are still bearing fruit. Catfacing doesn’t affect tomato flavor, so you can still eat the deformed tomato. Just cut out the brown, woody parts.

Slugs

Slugs love the soft skin of tomatoes, and if you mulch with straw or leaf litter, you may have a bumper crop of these slimy foes. You know slugs have been at work on ripening tomatoes when you see single holes in the fruit. Once a slug creates an opening in a tomato, the fruit is prone to attack by other insects and mold. The quickest way to catch slugs is by leaving boards out in the tomato patch. They’ll crawl under for shelter at dawn, and you can scrape them into a bucket of soapy water. Use slug bait throughout the growing season right up to frost to diminish the slug population. Choose pet-safe baits if your pooch visits the garden.

Late Blight

Late blight is the bane of tomato growers everywhere. This fungal disease arrives in your garden via fungal spores carried on the breeze. The disease grows best in moist conditions at temps of 60 F to 80 F. Once late blight hits your tomato patch, it races from plant to plant. The best way to beat it is to start applying fungicides from midway through the growing season on. More frequent sprays at lower rates are more successful at keeping the disease at bay.

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