Crepe myrtles, more commonly known as crape myrtle or crapemyrtle (Lagerstroemia spp.), are large shrubs or small multiple-trunk trees with flower clusters in whites, pinks, reds and purples. Most crape myrtle varieties thrive in U.S. Department of Agriculture plant hardiness zones 7 to 10 but some grow in USDA zone 6. Crape myrtles attract aphids, Japanese beetles and primrose flea beetles. Plants are susceptible to fungi that lead to powdery mildew and sooty mold.
Crape Myrtle Aphids
Crape myrtle aphids (Tinocallis kahawaluokalani) chew through tree leaves and twigs beginning in May -- with heavy infestations in July through early August. Yellowish-green crape myrtle aphids grow up to 1/2 inch long. Females produce eggs which hatch in the spring. Crape myrtle aphids eat sweet liquid sap from leaf bottoms. The insects may damage branch tips, crape myrtle flower buds and blooms. Crape myrtle aphids can often be controlled by high-pressure water spraying on tree foliage or picking the insects off by hand. Chemical remedies include synthetic solutions of permethrin, acephate, bifenthrin, deltamethrin, cyfluthrin or imidacloprid. Organic neem oil or insecticidal soap may also be effective. Follow label instructions carefully before applying any chemical controls. Predatory insects and birds may also help control crape myrtle aphids.
Japanese beetles (Popillia japonica) are oval-shaped, metallic-green and copper colored insects, about 1/3 to 1/2 inch long. Larvae feed on roots and grasses but adult Japanese beetles mostly eat leaf tissue, especially when exposed to direct sunlight. Female Japanese beetles lay their eggs in the soil, overwintering deeply into the ground. Eggs hatch, feeding on grass roots. From May to August, Japanese beetles eat crape myrtle flowers and leaf tissue between foliage veins. To control Japanese beetles, you can pick them off by hand or use a water spray, but homemade or commercially available products may be more effective, suggests Clemson University Extension. Traps, containing milky spore (Bacillus popilliae), placed at least 50 feet away from crape myrtle kill larvae but usually not adult Japanese beetles. Effective insecticides for use on crape myrtle may include lambda, permethrin, carbaryl, acephate, cyhalothrin, neem oil, cyfluthrin or inidacloprid -- the types and amounts of products to use depend on your growing landscape. Strong insecticides may kill natural predators of Japanese beetles.
Primrose Flea Beetles
Crape myrtle trees and shrubs may attract shiny, bluish-green primrose flea beetles (Altica litigate). Adults grow to about 1/4-inch long; they feed by chewing holes into crape myrtle leaves. Severe damage to growing tips may kill tree seedlings and young plants. Primrose flea beetles have natural enemies in field crickets (Gryllus pennsylvanicus), damsel bugs (Nabis spp.) and larvae of green lacewings (Chrysopa ornata). Removing weeds around crape myrtle trees may keep larvae from feeding. Destroying infested tree branches helps control current and new infestations.
Crape myrtle and other types of trees may be visited by glassy-winged sharpshooters (Homalodisca vitripennis); brownish-black insects with transparent wings. These leafhoppers grow to about 1/2 inch long, feeding on plant sap. Although glassy-winged sharpshooters cause only slight damage to crape myrtles, the insects’ excrement can lead to the transfer of Xylella fastidiosa bacteria, which can ultimately kill the plant. Cultural controls for the glassy-winged sharpshooter are not known, advises the University of California’s Integrated Pest Management program. However, inspecting and monitoring crape myrtle and other plants for possible insect infestations, then destroying infected limbs and greenery, can help keep bacteria from spreading.
Pests and Disease
Crape myrtle trees may develop molds and other bacterial disease. Powdery mildew (Erysiphe lagerstroemiae) causes a whitish-gray film to grow on leaves, flowers and buds. Shrubs and trees may have insects living on them if plant greenery is covered with sooty mold; black, gritty dust. Aphids, scales, whiteflies and mealy bugs excrete a sugary substance called honeydew, which hosts molds and fungi on crape myrtles and other trees. Sooty mold does not directly harm crape myrtles but the plants’ black powdered-covered leaves cannot easily absorb sunlight, which deters the photosynthesis process. Reducing aphid and other insect infestations helps to control sooty mold on crape myrtle trees and shrubs.