Leaf problems
Leaves are where most tomato problems show first. Dark spots on lower leaves are usually early blight, with target-like rings and yellow halos, or Septoria leaf spot, with many small spots that have pale centers; both work up the plant in wet weather. Even, pale yellowing of older leaves without spots points to nitrogen, while yellow new leaves with green veins point to iron and high soil . Leaves rolling upward in heat are usually harmless; twisted, cupped new growth suggests herbicide or a virus. See the pages on black spots, yellow leaves and curled leaves for details.
Fruit problems
Most fruit problems trace back to water. A dark, leathery patch on the bottom is , caused by uneven moisture that keeps calcium from reaching the fruit, not usually a lack of calcium in the soil. Cracks around the stem or shoulders follow a dry spell broken by heavy rain or watering. Grainy, mealy flesh most often comes from storing ripe fruit below about 55°F. Green fruit late in the season can ripen indoors if it has reached full size and a glossy shine. Single bites taken out of fruit in dry weather often point to squirrels.
Flowers but no fruit
Flowers that open and drop with no fruit behind them are usually a temperature problem. Tomatoes set fruit best when nights stay between about 55°F and 70°F; warmer nights, or days above about 90°F, make pollen sticky and infertile. Heavy nitrogen adds to the problem by pushing leaves over fruit. Keep plants watered and , hold off on nitrogen, and expect fruit set to pick up again when the weather moderates. Heat-tolerant varieties help where hot summers are the norm.
Wilting plants
For a wilting plant, check the time of day. Plants that droop on hot afternoons and recover by evening are coping with heat. A plant still wilted at 8 a.m. needs a soil check: dry soil means water, while soggy soil means roots may be rotting. If the soil seems fine, cut the lower stem lengthwise. Brown streaks under the skin point to Fusarium or Verticillium wilt, which often yellow one side first; milky threads streaming from a cut stem set in water suggest bacterial wilt, mostly in the South. Plants near a black walnut tree may be reacting to juglone.
Pests
For pests, look at the damage. Leaves and stems stripped overnight, with dark pellets of droppings below, point to tomato hornworms, green caterpillars up to 4 inches long that blend in with the stems. University of Wisconsin–Madison Extension suggests hand-picking them, or Bacillus thuringiensis kurstaki for widespread feeding. Fine speckling and webbing under leaves in hot, dry weather suggest spider mites. Clouds of tiny white insects that fly up when you brush a plant are whiteflies, which can spread tomato yellow leaf curl virus. Aphids cluster on new growth.
Habits that prevent most problems
A few habits prevent most of these. Keep 2–3 inches of mulch over the root zone, water deeply at the base on a steady schedule, and keep water off the leaves. Space and stake or cage plants for airflow, remove spotted lower leaves as soon as you see them, and grow tomatoes in a different spot each year. Choose varieties with disease resistance codes, such as V and F for the wilts, where those diseases have been a problem. If you can't match the symptoms, your local extension office can help identify a sample.
Before using any product, read the whole label. It must list the crop you’re treating, and its directions on amount, timing, protective gear, bees and days before harvest are legal requirements. If this page and the label disagree, follow the label.
Growing it again? When to plant tomato for your ZIP code
- Verticillium WiltLower leaves yellow with V-shaped browning; wilting in midday heat with partial evening recovery.
- Fusarium WiltOne-sided yellowing and wilting; stem cut lengthwise reveals brown or salmon-colored vascular tissue.
- Gray Mold (Botrytis)Gray-brown fuzzy mold on fruit, flowers, or stems — soft, collapsing tissue beneath the coating in cool, wet conditions.
- Early BlightDark spots with concentric rings on lower leaves that yellow and drop, working up the plant.
- Septoria Leaf SpotNumerous small circular spots with dark borders on lower tomato leaves, which then yellow and drop, progressing upward.
- Why are my tomato leaves turning yellow?Where the yellow starts points to the cause: lower, older leaves suggest nitrogen, early blight, Septoria, or age; new leaves suggest iron and soil pH; yellowing with wilting suggests Fusarium or Verticillium.
- What are the black spots on my tomato leaves?Black or dark-brown spots on tomato leaves are usually early blight or Septoria leaf spot — two common fungal diseases with different spot patterns that are managed much the same way.
- What is that black leathery patch on the bottom of my tomatoes?Blossom end rot is a calcium deficiency at the fruit level, usually caused by irregular watering rather than a lack of calcium in the soil.
- Why are my tomato plants wilting?If wilted tomatoes perk up by evening, it's usually heat. If they're still wilted the next morning, check the soil for dry or soggy roots first, then cut the stem to look for wilt disease.
- My tomato plants are full of flowers but no fruit is setting — why?Tomato flowers often drop without setting fruit when nights stay above about 70°F or below 55°F, or days top about 90°F — warm nights are a common cause in midsummer.