The crape myrtle bark scale ( Acanthococcus ) is a recently introduced pest from Asia that initially infested crape myrtles (Lagerstroemia spp.) in Texas during 2004. Since then, it has spread rapidly through the movement of plant material. The pest is currently in 12 states: Alabama, Arkansas, Georgia, Louisiana, Mississippi, New Mexico, North Carolina, Oklahoma, Tennessee, Texas, Virginia lagerstroemiae and Washington. It is one of the only scales known to infest crape myrtles.
The Facts About Crape Myrtle Bark Scale Common name: Crape myrtle bark scale (CMBS) Scientific name: Acanthococcus (Kuwana), formerly lagerstroemiae Eriococcus lagerstroemiae Kuwana Description: CMBS is relatively easy to identify. Adult females are felt-like white or gray encrustations that stick to crape myrtle parts ranging from small twigs to large trunks. When crushed, these scales exude pink liquid. On new growth and in heavy infestations, the scales may be distributed more uniformly on the branch. Up close, CMBS is white to gray and about 2 mm long. Crape myrtle bark scales may aggregate toward the undersides of young horizontal branches instead of the parts exposed to the sun. CMBS causes extensive honeydew deposits and the growth of black sooty mold.
The crawlers are pink, very small, and may not be noticed without a hand lens.
Life cycle: The small CMBS males are winged and will fly to find females and to mate. Once the females lay eggs, they die. The eggs remain protected within the white colored ovisacs until the crawlers (immatures) hatch and disperse onto the branches. Each female lays about 60 to 250 eggs, which may overwinter within their ovisacs, and then hatch during mid- to late-April to May. A second peak in crawler activity occurs in late summer. These mobile crawlers move out to new twigs and branches to settle down and begin feeding on the sugary phloem layer beneath the bark. Damage: Crape myrtles suffer aesthetic damage because of the CMBS infestations. These bark scales may not kill the plants, but there may likely be a reduction in plant vigor, number of flowers, and flower cluster size. Infested plants typically leaf out later than healthy plants. Branches and trunks can be covered in the white scale infestation. Another striking symptom is the extensive amount of black sooty mold that may completely cover the foliage, branches, and trunks. However, do not confuse the honeydew and resulting black sooty mold caused by an aphid infestation with that caused by the crape myrtle bark scale. Control: The most effective chemical control is a soil drench with either imidacloprid or dinotefuran. These systemic insecticides will move up into the plants and give control for at least a year. They are most effectively applied in spring as new plant growth begins.
Sprays for crawlers are best applied in the late April and May, then again in late summer when immatures appear. Use a bifenthrin spray mixed with 2% horticultural oil. Double-sided sticky tape wrapped around small branches can be used to trap the crawlers to see when they hatch and to base the timing of additional contact insecticide applications.
Natural predators may take a while to build up in numbers, but both lady beetles and mealybug destroyers are effective in controlling CMBS.