a branch covered in crapemyrtle bark scale

Crapemyrtle bark scale
Photo: Jim Robbins, Univ. of Ark. CES, Bugwood.org

Updated: August 16, 2022

Key points

  • Crapemyrtle bark scale (Acanthococcus lagerstroemiae) is a non-native type of soft scale insect that can be difficult to manage as their waxy body covering shields them from predators and certain pesticides. Learn more about scale insect groups and biology the Introduction to Scale Insects page.
  • This is becoming a pest of crapemyrtle and occasionally beautyberry and can cause leaf drop, poor growth and flowering, and possibly dieback when populations are high.
  • Target monitoring and control efforts to the vulnerable crawler stage.  Learn more about what to look for on the Monitoring for Scale Insects page.

Appearance

  • Mature female covers are rounded to hemispherical, white, and up to ¼” (6 mm) in diameter.
  • Male covers are elongated and white.
  • Crawlers are pink, turning darker or gray-brown.
  • close up of crapemyrtle bark nymph (immature)

    Crapemyrtle bark scale crawler (nymph)

    Photo: Jim Robbins, Univ. of Ark. CES, Bugwood.org

  • white male covers of crapemyrtle bark scale

    White male covers

    Photo: Michael Merchant, Texas Cooperative Extension, Bugwood.org

Common host plants

This scale species can be found on plants in at least fifteen plant families. 

  • The primary host is crapemyrtle (Lagerstroemia).
  • So far, the only other host being damaged in North America is American beautyberry (Callicarpa americana). Potential additional hosts include apple (Malus domestica), Kalm’s St. Johnswort (Hypericum kalmianum), and boxwood (Buxus). Outside the U.S. (for now), hosts also include fig (Ficus carica), pomegranate (Punica granatum), and Asian persimmon (Diospyros kaki).

Where to look

Crapemyrtle bark scale on trunk
Crapemyrtle bark scale infestation on bark of tree
Photo: Jim Robbins, Univ. of Ark. CES, Bugwood.org
  • All life stages will be found on twigs and small branches. Rarely, they can also be found on foliage.
  • Insects attracted to honeydew. Bees, wasps (including hornets), ants, and flies tend to forage on honeydew, but note that crapemyrtle aphids are a common pest on crapemyrtle that also produce honeydew.
  • Light infestations often start in the bark furrows and branch forks.
  • They also cluster around pruning cuts. Over-pruned crapemyrtle provides more habitat for scale to colonize the plant. Crapemyrtle over-fertilized with nitrogen may also boost scale populations.
The start of a crapemyrtle bark scale infestation
Look for white wax in the bark furrows for the beginnings of an infestation
Photo: Royal Tyler, Pro Pest and Lawn Store, Bugwood.org

Plant damage

  • Light to moderate infestations will produce honeydew, which can attract other insects (mainly flies, wasps, and ants) and support the growth of sooty mold.
  • Moderate to heavy or prolonged infestations may cause leaf yellowing and shedding, and plants might lose vigor. Weakened plants may not bloom as profusely or may delay bloom. Branch dieback and entire plant death have been reported in southern states.

Honeydew and Sooty Mold 

crapemyrtle leaves with heavy coating of sooty mold
Foliage and twig covered in sooty mold
Photo: UMD-IPMnet

Life cycle

  • There are 2 to 4 generations per year, possibly overlapping, in Maryland. As a relatively newly-arrived pest, this is still being studied.
  • The crawler emergence period depends on temperature and can vary slightly from year to year. Due to the unknown details of this scale’s reproduction in Maryland, monitoring and treatment may need to occur several times a year to be effective. In southern states, the peak of the first generation of crawlers was between mid-March and early May.
  • The overwintering stage is still being determined.

Management

Refer to our general scale management recommendations for both chemical-based and pesticide-free options. When pesticides are warranted, a combination of dormant oil applications and the use of systemic or growth-regulating insecticides is the most effective approach. For large populations, scale suppression may require more than one year of intervention, and professional pesticide applicators will be needed to apply certain treatments. Mature trees should be evaluated by a certified arborist.

The unknown details for crawler emergence periods for this species means that monitoring and treatment need to occur several times a year to be effective. If you do not wish to use pesticides and are not obtaining good control from manual removal efforts alone, remove and replace the infested plants.

Introduction to Scale Insects
Details for monitoring and pesticide use timing

Just before the expected emergence period for each generation, start monitoring for crawlers. Since weather trends can shift date ranges, a more reliable prediction of timing can be made using Growing Degree Days and Plant Phenological Indicators.

Clemson University reports that southern states predict to see a peak of first-generation crawler activity around 646 degree days.

More information regarding degree days and plant phenological indicators is not yet available for this species in the mid-Atlantic.

Additional resources

Report findings of Crape Myrtle Bark Scale for research | StopCMBS.com 

Crape Myrtle Bark Scale | District Department of Transportation Urban Forestry Division (Washington, DC)
 

Author: Miri Talabac, Horticulturist Coordinator, HGIC 2022