Because privet (Ligustrum spp.) shrubs don’t mind clipping and pruning, they've traditionally been used as hedge plants. These evergreen, semi-evergreen or deciduous shrubs grow in U.S. Department of Agriculture plant hardiness zones 3 through 10, depending on the species. Examples include amur privet (Ligustrum amurense), which grows up to 15 feet tall and 10 feet wide and grows in USDA zones 4 through 7, and 10-foot-tall and wide common privet (Ligustrum vulgare), which grows in USDA zones 5 through 8. Considered invasive in some areas, privet hedges prefer moist, well-draining soil in full sun or partial shade. A few problems can cause privet leaves to curl.
Tiny pests, including aphids, scale insects and whiteflies, can have a big impact on privet hedges in spring and summer. Often found on the undersides of leaves, these bugs suck the juices from the plant and cause leaf curl and wilting. Privet mites may cause stunted growth and leaf curl in California privet (Ligustrum ovalifolium), which grows in USDA zones 7 through 10. Mites often attack the tender, new growth on privet hedges.
You can remove a light infestation of aphids, whiteflies, scales or mites with a strong spray of water, or spray heavily infested privet hedges with insecticidal soap. Dilute 2 1/2 tablespoons of insecticidal soap in 1 gallon of water and spray the entire plant, including the undersides of leaves. You can apply it again after seven to 10 days. If you are pregnant or nursing, have someone else apply pesticides, including insecticidal soap. Keep pesticides out of the reach of children.
Active in the spring in deciduous privet and all year in evergreen varieties, anthracnose fungi spread in splashing water and attack twigs and leaves. This disease causes curled, brown or distorted leaves and leaf drop, particularly in young privet leaves. Verticillium wilt fungus attacks privet roots and interferes with water uptake, resulting in curled or wilted leaves. Privet leaves may suddenly turn brown or yellow and drop off the hedge. The fungi can stay in the soil for years after you remove an infested plant.
You can plant anthracnose-resistant privet species, including amur privet. To prevent the spread of anthracnose, rake and dispose of fallen leaves in the fall. Plant the shrubs 2 to 4 feet apart to allow enough air circulation. Prune and destroy verticillium-infected branches, and dip tools in a solution of 1 part rubbing alcohol and 1 part water between cuts. Keep children and pets away from sharp pruning tools and disinfectants. If the privet shrub has died, remove the entire shrub with the roots intact. Do not plant privet hedges where verticillium-infected plants have grown.
If your privet hedges have curled leaves in hot, dry weather, make sure they are getting enough water. Young plants are particularly sensitive to water stress. Too much water or poorly drained soil can cause curled leaves because the roots and plant tissue die and cannot send water to the leaves. Magnesium deficiency can cause leaf curl in foliage plants such as privet hedges. To treat this deficiency, water the soil twice a year with 1 teaspoon of Epsom salts diluted in 1 gallon of water, recommends North Carolina State Cooperative Extension.