Why Are My Tomato Leaves Curling? Leaf Roll, Herbicide or Virus
Most curled tomato leaves are a harmless stress response. A few patterns are not. Here is how to tell which one you are looking at.
If the lower leaves roll upward, stay green and feel thick and leathery, you are probably looking at physiological leaf roll, a stress response that does little harm. Keep watering steadily and leave the plant alone. If the newest leaves are twisted or roll downward, suspect herbicide. If new leaves are cupped, small and yellow at the edges on a stunted plant, suspect a virus and remove the plant.
Look-alike table
| Cause | Where and how it curls | Other clues | Harm to the crop | What to do |
|---|---|---|---|---|
| Physiological leaf roll | Lower leaves first; upward toward the midvein | Leaves stay green, thick and leathery | Little or none | Water evenly; wait |
| Herbicide drift (2,4-D, dicamba) | Growing tips; leaves roll downward and twist | Twisted stems, veins running in a parallel pattern, deformed fruit | Can be serious | No remedy; prevent drift |
| Herbicide in compost, manure or hay | Twisted, cupped leaves after adding new material | Damage may show only when fruit sets | Can be serious | Stop using the material; run a pot test |
| Tomato yellow leaf curl virus | New leaves cup; leaves smaller than normal | Yellow edges, stunting, flower drop, whiteflies | Serious | Remove and bag the plant |
| Tomato mosaic virus | Leaves roll, with small leaflets | Mottled color; internal browning in fruit | Affects fruit quality | Remove the plant |
| Broad mites or wind | Varies; can mimic herbicide injury | Mites are too small to see easily | Varies | Send a sample to your extension office |
Physiological leaf roll: the harmless one
This is the most common reason for curling. It usually starts on lower leaves, with the edges cupping upward and then rolling in toward the midvein. Rolled leaves can look alarming, but they stay green.
Triggers include heat, drought, too much water or nitrogen, severe pruning, root damage, early planting and transplant shock. In other words, the plant is telling you it was stressed. Clemson’s factsheet on rolling tomato leaves says the effect on fruit production and plant growth is minimal. Indeterminate (vining) varieties tend to show it more than determinate (bush) types.
There is nothing to treat. Water deeply and evenly, keep a layer of mulch on the soil, and go easy on nitrogen and pruning. Our guide to how often to water vegetables covers a steady routine.
Herbicide injury
Tomatoes are among the most sensitive garden plants to growth-regulator weed killers such as 2,4-D and dicamba, and tiny amounts carried on the wind can cause damage. Unlike leaf roll, this injury concentrates on the upper part of the plant and the growing points. Leaves roll down rather than up, stems twist, and fruit can be misshapen.
Think back over the past couple of weeks: did anyone treat a lawn, fence line or roadside nearby? There is no way to reverse the damage. Plants that were only lightly exposed may grow out of it, and new growth is the thing to watch. If you know a product landed on your plants, check its label or ask your extension office before eating the fruit.
To prevent it, keep weed-and-feed products and sprays away from the vegetable garden, spray only on calm days, and rinse sprayers thoroughly or keep a separate one for herbicides.
Herbicide that arrives in compost or mulch
Three persistent herbicides (picloram, clopyralid and aminopyralid) can survive in hay, grass clippings, manure and compost. NC State Extension reports that breakdown is especially slow in manure and compost piles, and that tomato damage may not show until plants set fruit.
If you suspect a load of compost or manure, do a simple pot test. Fill several pots with a half-and-half mix of the material and potting mix, fill several more with potting mix alone, and sow peas or beans in all of them. Grow them for two to three weeks. If the plain pots grow normally and the mixed pots do not, stop using that material.
Viruses
Tomato yellow leaf curl virus is spread by whiteflies and threatens tomatoes mainly in the southern US. It is less of a problem where whiteflies cannot survive winter, although infected transplants can carry it north. Symptoms can take up to three weeks to appear. New leaves cup and turn pale, edges yellow, plants stay short and bushy, and flowers drop. Young plants may set no fruit at all.
There is no treatment for an infected plant. Pull it and bag it, and keep it out of the compost. What to do with diseased plants explains why. To protect the rest of your garden:
- Buy clean transplants and check the undersides of leaves for whiteflies before planting.
- Choose resistant varieties next year. Seed packets and catalogs will say so.
- Keep nightshade and other weeds down, since whiteflies can move in from them.
- Use a yellow sticky trap to monitor for whiteflies.
- If whiteflies are heavy, insecticidal soap or neem aimed at leaf undersides can reduce them. Use one product at a time, never mix products, and follow the label.
Tomato mosaic virus causes rolled leaves together with mottled color and small leaflets. It too has no treatment, so remove affected plants.
How to check in five minutes
- Note which leaves are curling: old and low, or new and high.
- Check the direction. Upward suggests leaf roll or a virus; downward with twisting suggests herbicide.
- Look at the color. Solid green suggests leaf roll. Yellow edges or mottling suggest a virus.
- Inspect stems and growing tips for twisting or distortion.
- Shake a leaf and watch for small white flying insects.
- Ask yourself what changed recently: a heat wave, a heavy pruning, nearby spraying, a new load of compost.
- If it still does not add up, send a sample or clear photos to your county extension office.
Bottom line
Green, leathery, upward-rolled lower leaves are rarely a problem. Twisted new growth points to herbicide, and cupped, yellow-edged, stunted growth points to a virus. Fix the watering for the first, prevent drift for the second, and remove the plant for the third. Compare other symptoms with our guide to tomato leaves turning yellow.
FAQ
Will curled tomato leaves uncurl?
Leaves with physiological roll may stay rolled, and that is fine. What matters is that new growth looks normal and the plant keeps setting fruit.
Should I cut off curled leaves?
No, not for leaf roll. The leaves are green and still working, and they shade the fruit. Remove leaves only if they are diseased.
Does leaf curl reduce the tomato harvest?
Physiological leaf roll has little effect. Herbicide injury and viruses can reduce or end the harvest.
Can I eat tomatoes from a plant with curled leaves?
Fruit from a plant with physiological leaf roll is fine. If herbicide reached the plant, check the product label or ask your extension office first.
