Leaf Curl on a Citrus Tree

When the leaves on a citrus tree curl, it's the tree's response to an unfavorable environment. This response may be a result of the tree's water needs, pests or chemical sprays. Prevention or early intervention are the best ways to minimize damage.

"Citrus" is a collective term that categorizes fruit-bearing trees in varied plant groups. The most familiar citrus trees are Citrus, Fortunella and Poncirus species. Although different species grow in different climates, some grow in the range of U.S. Department of Agriculture plant hardiness zones 5 through 12. The familiar lemon tree (Citrus limon) grows in the warm climates of USDA zones 9 through 11.

The University of Arizona Cooperative Extension paints a word picture to describe the appearance of drought-stressed citrus leaves -- "cigar leaf curling." If a citrus tree doesn't get enough water, its leaves curl inward from the edges.

Watering needs vary, depending on climate, species, soil type, age and size of a tree. General guidelines include: don't water until the top 6 inches of soil are dry, and then water the soil around the citrus tree to a depth of 2 feet -- from the trunk to just beyond its outermost branches, called the "drip line."

Strong winds, which batter citrus trees in spring as new leaves are opening, can dry out the leaves, causing them to curl. This is a seasonal disorder that typically does not cause serious damage.

Insects including Asian citrus psyllids, aphids and leafminers feed on citrus leaves, causing the leaves to curl. Young, tender leaves are more vulnerable to feeding damage. Leafminers tend to make the leaves look wrinkled or puckered. A severe aphid infestation may cause new leaves to be distorted.

Control Asian citrus psyllids and aphids by using a soap-oil spray. The University of Hawaii at Manoa recommends making a homemade soap-oil concentrate by combining 1 tablespoon of a mild dishwashing liquid with 1 cup of vegetable oil, such as peanut, corn or safflower. Shake the soap-oil concentrate thoroughly and mix 1 to 2 teaspoons into 1 cup of water. Pour the solution into a garden sprayer and spray all leaf surfaces thoroughly, particularly the undersides. Spray once a week until the insects are gone.

Insecticides typically are ineffective for controlling leafminers, but leafminers don't usually cause catastrophic damage. It's best to let natural predators control these insects instead of using insecticides.

Asian citrus psyllid spreads a bacterial disease that threatens citrus trees across the U.S. If you find these pests on your tree, check the SaveOurCitrus.org page for information on what you should do. Most areas where citrus is grown commercially are under a quarantine and many require you to report the pests if you find them on a tree in your yard.

Broad mites are tiny arachnids -- relatives of spiders -- that cause leaf-curling damage similar to that of insects. Although broad mites prefer feeding on citrus fruits, they also feed on the leaves.

Spray all leaf surfaces thoroughly with a ready-to-use insecticidal soap as a less-toxic option to using a synthetic chemical miticide.

Herbicides used to control weeds, such as glyphosate, and plant growth regulators, such as 2,4-D, can cause citrus leaves to curl. Whether from intentional spraying or chemical drift, these weedkillers will damage citrus trees.

Use all chemicals -- synthetic or organic -- only according to label directions and cautions.

Don't spray chemicals on windy days.

Wear protective clothing and safety glasses when spraying chemicals on citrus trees.

Make sure any chemical you use is safe to use on fruit trees.