Fruit trees, including figs, cherries, nectarines, peaches and lime, are subject to a number of conditions that cause their leaves to curl. Pests, diseases and improper growing conditions reduce the plant's health and increase susceptibility to developing the condition. Identify the exact cause of the problem and rectify immediately to restore your fruit tree back to its optimal health and vigour.
Inspect the curled leaves of the fruit tree and note the season to streamline the possible causes. While fungal diseases are rampant in spring, pest problems usually arise in middle to late summer. Most fungal diseases require moist and humid conditions to spread. If you fail to notice pests or symptoms of diseases, re-evaluate your watering or fertilising practices.
Aphids, leaf miners, mealybugs, leaf rollers and whiteflies cause the foliage of fruit trees to curl or roll. Aphids, mealybugs and whiteflies are tiny insects that suck essential juices from the foliage, causing leaves to turn partially or completely yellow and curled. Leaf miners and leaf rollers are larvae of tiny moths that burrow through the leaves of fruit trees, causing them to curl and distort in shape. Because stressed fruit trees are more susceptible to pest damage than healthy ones, adopt good cultural practices to prevent infestations. Douse the pests with a spray of water from a hose, or use a low-toxicity insecticide specifically formulated to treat the particular insect.
Fungal and bacterial diseases such as powdery mildew, leaf curl and cankers cause the foliage of fruit trees to curl. Initial symptoms of powdery mildew include a delicate myceliumlike growth on the leaves that develops into powdery whitish-grey patches. Left untreated, the leaves begin to curl and fall prematurely. The fungus Taphrina deformans causes the leaves of a number of fruit trees to curl. The leaves of newly infected trees appear thicker than normal before curling and turning purplish-red. Left untreated, infected leaves die and fall off the trees. Symptoms of fruit tree cankers include swollen branches and curled leaves. Prune infected parts of the tree with sterilised pruning equipment to prevent the disease from spreading. Apply a registered fungicide to treat large infections, and rake fallen leaves and plant debris to prevent fungal spores from overwintering near the trees.
Improper cultural practices cause the leaves of fruit trees to curl. Under- or overwatering a tree causes its leaves to curl inward. Excessive exposure to direct sunlight, especially during the summer, coupled with insufficient soil moisture also causes the leaves to curl. Feeding the tree a high-nitrogen fertiliser attracts pests such as aphids that cause curling foliage.