Curled Tomato Leaves: Stress or Curly Top?

Seeing curled leaves on your tomato plants can be alarming, but curled leaves do not always mean disease. In many cases, the plant is simply reacting to stress.

Physiological leaf roll is a common response to growing conditions. It usually begins on older leaves near the bottom of the plant. The edges of the leaves cup upward and may roll inward, sometimes forming a tight, tube-like shape. Even though the leaves look unusual, the plant generally stays green, continues growing, and keeps producing fruit. Fruit quality and yield are usually not seriously affected.

Several things can trigger physiological leaf roll. Hot weather, drought, uneven watering, overly wet soil during high temperatures, heavy pruning, too much nitrogen, phosphorus deficiency, or a heavy fruit load can all contribute. Some tomato varieties are also more prone to leaf roll than others. The best response is usually simple: keep soil moisture as even as possible, avoid overfertilizing, and do not remove too much foliage at once. During extreme heat, temporary afternoon shade may also help reduce stress. There is no need to remove the plant just because the leaves are rolled.

Beet curly top disease is different. It is caused by Beet curly top virus and is spread by the beet leafhopper. Tomatoes are commonly affected, but peppers, beans, squash, table beets, Swiss chard, melons, cucumbers, and many weeds can also serve as hosts.

Curly top causes more than curled leaves. Infected plants may become yellow and stunted. Leaves can look thick, leathery, twisted, or brittle, and the veins may turn purple. New growth may be distorted, fruit production may slow or stop, and young plants can die. Unlike physiological leaf roll, plants infected with curly top do not recover.

Take a look at the whole plant before deciding what is wrong.

Is the plant still green and growing normally, with curling mainly on the older, lower leaves? Is it still setting and ripening fruit? That points more toward physiological leaf roll.

Is the plant stunted, yellowing, brittle, or declining? Are the newest leaves distorted? Do you see purple veins, leathery foliage, or very little fruit? Those symptoms are more concerning for beet curly top.

Plants suspected of having curly top should be removed because they will not improve. Managing nearby weeds may help reduce possible host plants. Young transplants can also be protected with row cover or shade cloth while they are becoming established, as long as row covers are removed when pollination is needed.

The bottom line: Leaf curl by itself does not equal curly top. Look at the plant’s color, growth, leaf texture, fruiting, and overall health before reaching a conclusion.

Interested in learning more?

• University of Idaho Extension — Physiological Leaf Roll of Tomato
• Oregon State University Extension — Physiological Leaf Roll of Tomato
• Utah State University Extension — Curly Top of Tomato