Common Tomato Plant Problems and How to Fix Them

Written by Susan B.

Most tomato troubles fall into three groups: watering and weather disorders like blossom end rot, cracking, and dropped blossoms; pests like hornworms, aphids, and spider mites; and diseases like blight and wilt. The good news is that the most common complaint, blossom end rot, is not a disease at all but a watering problem, and the single best fix for a long list of these issues is consistent, deep watering plus a layer of mulch. Reach for cultural fixes first, choose disease-resistant varieties, and save sprays for last.

Problem	Likely cause	What to do
Blossom end rot	Uneven watering keeps calcium from the fruit (not a disease)	Water deeply and evenly; mulch
Cracking or splitting	Irregular watering, rapid growth after rain	Keep soil evenly moist; mulch; crack-resistant varieties
Catfacing	Cool temperatures during flowering	Plant after it warms; smooth-fruited varieties
Sunscald	Too much direct sun on fruit after leaf loss	Keep a full leaf canopy; do not over-prune
Blossom drop	Heat or cold at flowering stops pollination	Wait for milder weather; keep plants watered
Hornworms	Large green caterpillars eating leaves and fruit	Handpick; let natural enemies work
Early or late blight	Fungal leaf spots in wet, humid conditions	Water at the base; remove infected leaves; rotate
Fusarium or Verticillium wilt	Soilborne fungi; one-sided yellowing and wilt	Plant VFN-resistant varieties; rotate; remove debris

Watering and Weather Problems (Physiological Disorders)

The most common tomato complaint of all is blossom end rot: a dark, sunken, leathery patch on the bottom of the fruit. It looks like a disease, but it is not. As University of California IPM puts it, blossom end rot is not caused by a pathogen and there are no pesticide solutions; it happens when the fruit does not get enough calcium, which is almost always a watering problem rather than a shortage of calcium in the soil.^[1] The University of Minnesota is blunt that it does not mean your soil lacks calcium, and that uneven soil moisture, root damage, or too much nitrogen keep the plant from moving calcium into the fruit.^[2] The fix is not calcium sprays or crushed eggshells; it is steady, deep watering so the soil never swings between bone dry and soggy, plus a layer of mulch to even out the moisture.

Cracking and splitting come from the same root cause as blossom end rot: uneven water. When a dry spell is followed by heavy watering or rain, the inside of the fruit grows faster than the skin and it splits. The UC IPM remedy is to keep a uniform water supply through irrigation or mulch, keep a full leaf canopy to shade the fruit, and choose crack-resistant varieties.^[3] Sunscald is a related problem: when fruit loses its leaf cover, intense direct sun scalds it into a pale, leathery patch, so the answer is to keep the plant vigorous and well leafed rather than over-pruning it.^[4]

If your plant flowers but will not set fruit, the usual culprit is temperature. Tomato pollen stops working in extreme heat or cold: University of Missouri IPM notes that once days climb past about 85 degrees F, or nights stay above about 70 degrees F, the pollen turns non-viable, and nights below about 55 degrees F cause blossom drop too.^[5] Iowa State puts the comfortable fruit-setting range at roughly 70 to 85 degrees F during the day.^[6] There is no fix except milder weather, so keep the plant healthy and watered until it arrives. And if the lower leaves simply roll upward in hot weather, relax: UC IPM confirms physiological leaf roll is not caused by a pathogen, needs no action, and will not harm the plant or its fruit.^[7]

Tomato Pests

When something is actually eating your plant, start with the simplest controls. The tomato hornworm is the big one: a fat green caterpillar that strips leaves and chews green fruit, leaving large dark droppings below. UC IPM advises handpicking or snipping them and letting natural enemies such as parasitic wasps keep them in check.^[8] Aphids cluster on new growth and leave sticky honeydew; a strong spray of water early in the day knocks them off, most plants tolerate moderate numbers, and too much nitrogen only makes them worse.^[9] Spider mites appear in hot, dry, dusty weather as fine stippling and webbing, and the same tactic works: regular, forceful spraying with water aimed at the undersides of the leaves usually keeps them down, along with avoiding water stress.^[10] Whiteflies and flea beetles round out the usual suspects; for all of these, handpicking, water sprays, and protecting natural enemies come before reaching for anything stronger.

Tomato Diseases

Tomato diseases are far easier to prevent than to cure, so identification matters. Early blight shows up first on the older, lower leaves as leathery brown spots with a target-like pattern of concentric rings; UC IPM manages it with crop rotation and by avoiding overhead watering.^[11] Late blight is the more dangerous cousin, favored by cool, wet, humid coastal weather: it causes irregular water-soaked lesions and a white, downy growth on the undersides of the leaves, and the response is certified transplants, no sprinkler irrigation, and destroying infected debris.^[12] The two soilborne wilts are worth knowing because they cannot be cured once they take hold. Fusarium wilt turns the plant yellow starting on one side or one branch, with brown streaking inside the stem, and the main defense is planting resistant varieties marked with an F.^[13] Verticillium wilt looks similar but favors cooler soils, and its resistant varieties are marked with a V.^[14] Those letters, along with N for nematodes, are why gardeners look for VFN-resistant tomatoes. A wilt disease is different from a plant that simply wilts in dry soil and perks back up after watering; the disease shows one-sided yellowing and internal brown streaking that watering does not cure.

How to Prevent Most Tomato Problems

Most of these problems trace back to a handful of habits. Water deeply and evenly, and mulch to hold that moisture steady; this one practice alone prevents blossom end rot and cracking and eases heat stress.^[1] Choose VFN-resistant varieties to sidestep the soilborne wilts that have no cure.^[13] Rotate where you plant tomatoes each year, and clean up and destroy infected debris to break disease and pest cycles.^[11] Water at the base of the plant early in the day rather than overhead, so the leaves stay dry and blight has less chance to take hold.^[12] Keep a full leaf canopy instead of over-pruning, which guards against sunscald,^[4] and go easy on nitrogen fertilizer, which otherwise feeds aphids and worsens blossom end rot.^[9] When a problem goes beyond what these cultural steps can handle, your local UC Master Gardeners and UC IPM have current, region-specific guidance. For the basics of growing great tomatoes in the first place, see our guide to growing tomatoes and our tips for caring for tomato plants.

Not sure what you are looking at? Bring a photo or a sample to any Green Thumb Nursery and our team can help you tell a watering problem from a pest or a disease and point you to the right fix. For a head start on keeping trouble out, see our tips to keep your vegetable garden pest-free.

Tomato Problems FAQ

What is wrong with my tomato plant?

Start by sorting the symptom into one of three groups: a watering or weather disorder (like blossom end rot, cracking, or dropped blossoms), a pest (like hornworms or aphids), or a disease (like blight or wilt). The most common issue by far, blossom end rot, is a watering problem rather than a disease, so check your watering before you reach for any spray.^[1]

What causes blossom end rot and how do you fix it?

Blossom end rot is the dark, sunken patch on the bottom of the fruit. It is not a disease and has no pesticide fix; it happens when uneven watering keeps calcium from reaching the fruit. The cure is consistent, deep watering plus mulch, not calcium sprays or eggshells, since the soil almost always has enough calcium already.^[1]

Why are my tomatoes cracking or splitting?

Cracking comes from uneven water, when the inside of the fruit grows faster than the skin after rain or heavy watering follows a dry spell. Keep soil moisture even with regular watering and mulch, shade the fruit with a full leaf canopy, and choose crack-resistant varieties.^[3]

Why are my tomato flowers falling off without making fruit?

Temperature. When days get much hotter than about 85 degrees F, or nights are too hot or drop below about 55 degrees F, tomato pollen stops working and the flowers drop without setting fruit. There is no fix but milder weather; keep the plant healthy and watered until conditions ease.^[5]

How do you treat tomato blight?

Blight is hard to cure, so prevention is the real answer: remove and destroy infected leaves, water at the base rather than overhead so foliage stays dry, rotate your planting spot, and avoid crowding. Late blight in particular spreads fast in cool, wet weather, so act early and clear out affected plants.^[12]

Sources

• [1] UC IPM, Blossom End Rot: ipm.ucanr.edu
• [2] University of Minnesota Extension, Tomato Disorders: extension.umn.edu
• [3] UC IPM, Fruit Cracks on Tomatoes: ipm.ucanr.edu
• [4] UC IPM, Sunscald on Tomatoes: ipm.ucanr.edu
• [5] University of Missouri IPM, Understanding Tomato Fruit Set: ipm.missouri.edu
• [6] Iowa State Extension, Tomatoes Flowering but Not Setting Fruit: yardandgarden.extension.iastate.edu
• [7] UC IPM, Physiological Leaf Roll in Vegetables: ipm.ucanr.edu
• [8] UC IPM, Hornworms: ipm.ucanr.edu
• [9] UC IPM, Aphids: ipm.ucanr.edu
• [10] UC IPM, Spider Mites: ipm.ucanr.edu
• [11] UC IPM, Early Blight on Tomatoes: ipm.ucanr.edu
• [12] UC IPM, Late Blight: ipm.ucanr.edu
• [13] UC IPM, Fusarium Wilt on Tomatoes: ipm.ucanr.edu
• [14] UC IPM, Verticillium Wilt on Tomatoes: ipm.ucanr.edu

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