What Causes Leaf Curl On Tomato Plants?

Leaf curling of tomato plants is a common problem. Identifying the real cause of the curling leaves as early as possible is crucial. It helps you take the necessary steps to save your crop. Why do the leaves curl on my tomato plants?

Tomato plant leaves can twist or curl for three main reasons. Exposure to chemicals, biological factors, and environmental stress are those causes. You can determine the reason for leaf curling by observing the plants for a few days. 

Observe whether all or only a few leaves are curling. Determine if the curling leaves are old or new. Both new and old leaves can roll at the same time. Identify whether the curling is upward or downward. See if any symptoms appear on other parts of the plant as well.

If tomato leaves curl upward, it is most likely due to environmental stress. Downward curling and twisted growth show exposure to drifting herbicides. 

Curling on older leaves at the bottom of the plant is often a sign of environmental stress. The oldest leaves undergo physiological leaf rolling first. Leaf curling may occur both inwards and upwards on small leaves.

Some viruses, herbicides, and broad mites often damage new foliage. Herbicide residue is most likely causing the upper, small leaves to curl downward. Young leaves curling with rust-colored patching underneath show broad mites. Virus symptoms often appear on the upper leaves first.

What Causes The Tops Of Tomato Plants To Curl?

Environmental Causes

Heat, Drought, And Windy Weather 

During high hot weather, tomato leaves curl and twist upwards. It helps them shield themselves from water loss. Heat and low humidity cause the edges of tomato leaves to die back, twist and roll. Windy weather can also dry out tomato plants, resulting in curled leaves. 

Shelter your tomato plants from strong, drying winds. You can create a windbreaker with other plants, a fence, or a canvas. Shield them from direct sunlight and provide enough shade.

This physiological leaf rolling of tomatoes has minimal impact on yield or quality. A critical state can cause flowers to fall and fruit to be fewer in number.

The tomato crop thrives during the summer. But high temperatures and heavy rains can stress them. Maintain the health of your plants at all times. Leaf curl is less likely to occur on healthy tomato plants.

The leaves can curl when planting tomatoes too early during the cold season. First, the lower leaves curl upwards, then roll inward lengthwise. Also, the leaves will become thick and leathery but remain green. 

The ideal temperature to plant tomatoes will be 70-79 0F during the day and 61-65 0F at night. 


Chemical Causes

Nutrient Imbalance

Nitrogen-overfertilized tomatoes may have thicker and greener leaves that curl upward. Phosphorus deficiency can also cause leaf curling. 

Herbicide Drift

Herbicides drifting in the air can cause tomato leaves to curl. Tomato plants are sensitive to herbicides like glyphosate and dicamba. Other hormone-type herbicides also affect them.

Herbicides drifting from nearby farms and gardens can damage your sensitive tomato plants. Winds of 5 mph can move these herbicides up to a mile. 

Wait and see if your new growth returns to normal if herbicide drift has already occurred. Plants may be able to outgrow injuries if new shoot growth is usual at 4-6 weeks left in the growing season.

Harvest any salvageable fruit and pull up the affected plants if symptoms persist. Growing tomato plants in a greenhouse is an ideal way to prevent drifting herbicides.

Whenever the wind blows toward sensitive crops, avoid spraying herbicides. You can use drift-reducing spray additives. Prevent air movement by reducing spray application speed.

Herbicide Residue

Herbicide residues in the soil or manure can lead to cupped or distorted tomato leaves. Farmers use chemicals like aminopyralid or clopyralid as active ingredients in weed killers. 

These chemicals can remain on treated hay and hay products for months. Also, they can survive in the manure of cows and horses that consume treated hay.

Avoid using manure from animals that have eaten forage or hay from treated areas. You can speed up the breakdown of aminopyralid by keeping the soil moist and warm. Buy mulch, manure, or compost only from reliable sources. Use chicken manure as it does not have this issue.

Biological Causes

Broad Mites

Broad mites feed on young tomato leaves and flowers. During feeding, they inject toxins that cause leaves to twist and deform. Infested leaves and fruits may turn bronze or russet on the underside.

The broad mite is invisible to the naked eye or a magnifying glass. Their presence will be evident through plant damage.

Broad mites may infest your crop via greenhouse transplants. Legs and antennae of whiteflies also can carry the disease. To treat them early, you can use a horticultural oil like Neem oil or insecticidal soaps. 

Use a sulfur-based miticide to treat moderate infestations. Make sure your tomato cultivar tolerates sulfur before applying it. Avoid applying miticide when the temperature is over 90 0F.

If the broad mite infestation is severe, pull up the plants and destroy them. You can also introduce predatory mites that attack and consume broad mites. They are more effective at an early stage. 


Many viruses cause tomato leaf curling and stunted growth. You can identify the relevant virus based on other symptoms and transmission methods. 

Tomato mosaic and yellow leaf curl virus are the two common viruses that cause tomato leaf curl. The geminivirus group often results in tomato leaf twisting or deformation.

Farmers may mistake the initial virus symptoms for damage from phenoxy-based herbicides. As the virus disease progresses, yellow-green mosaic patterns appear on the leaves. 

Whiteflies carry the yellow leaf curl virus. The new leaves will appear cupped and pale green. Leaf edges will turn yellow, and the undersides may turn purple. 

Control the whitefly population with insecticidal oil and soap. Save healthy plants by identifying the virus early and pulling out infected ones. Avoid composting infected plants or leaving them on the ground. They will continue to spread, so destroy or burn them.

Can A Tomato Plant Recover From Leaf Curl?

The leaf curl caused by environmental stress is most often a temporary condition. Water your tomato plants well and mulch around their bases to prevent the soil from drying. It will help them recover faster. As soon as the weather stabilizes, the plants will return to normal. 

If you prevent excessive fertilization, leaf curl will normalize in nutrient-enriched conditions. Control infection spread by pruning indeterminate tomato plants. You will have to remove the affected plants if the infection damage is severe.

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