Crapemyrtle Bark Scale in Home Gardens

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

• 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.

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 

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.

Natural predators 

Lady beetle larvae feed on crapemyrtle bark scales and help control their populations naturally. Some types of larvae in this group (Hyperaspis and Cryptolaemus) may be confused easily with crapemyrtle bark scale. There are a couple of ways to tell them apart:

• The lady beetle larvae, particularly in their later life stages, are larger and ‘fluffier’ than CMBS. Their waxy cover is more filamented and resembles a thick fleece blanket.
• The lady beetle larvae move more quickly than the bark scale, which does not move at all once it reaches the later white stages.
• The lady beetle larvaes' protective waxy cover is attached to the body underneath, while CMBS’ is not. Flip the insects over and look for legs. A lady beetle larva has six legs.

Management

Biological control

Look for the natural predators (lady beetle larvae), as noted above. In 2024, the University of Maryland Extension found that many populations of CMBS collapsed or were seriously reduced, seemingly due to natural predators. Natural predators can be supported in your landscape by avoiding or limiting the use of pesticides and providing a variety of flowering plants which provide food resources to these beneficial insects at different life stages.

Refer to our general scale management recommendations for further information.

Chemical control

As a last resort, if 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 

Waxy Lady Beetles Come to the Rescue of Pest-Plagued Crapemyrtles | University of Maryland "Bug of the Week," May 27, 2024

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

Author: Miri Talabac, Horticulturist & Coordinator, HGIC 2022. Rev. August 2024