Crape Myrtle Bark Scale: Spring Monitoring and Management Strategies

​Rafia Khan, Ph. D.
Assistant Professor and Extension Specialist
Texas A&M AgriLife Research and Extension Center
Overton, TX.

Crape myrtle bark scale (CMBS), Acanthococcus lagerstroemiae, has become a persistent and economically important pest of crape myrtle in Texas landscapes and nurseries. Early spring is a critical time to detect and manage this pest before populations build and become more difficult to control.

Identification and Early Signs

CMBS primarily colonizes trunks, branches, and twigs of crape myrtle. The most recognizable sign is the presence of small, white to gray, felt-like encrustations on the bark. These are the adult females, which produce a waxy covering that protects them from environmental stress and some control measures.

One of the earliest and most noticeable symptoms in spring is the development of black sooty mold on the bark and surrounding surfaces. This mold grows on honeydew excreted by the feeding scales and often serves as the first visual cue for infestation. Heavy infestations can lead to reduced plant vigor, poor flowering, and aesthetic decline, key concerns for both growers and landscape managers.

During early spring, overwintering populations begin to resume activity. Crawlers (the mobile, immature stage) start emerging as temperatures increase, making this the most vulnerable stage for management interventions.

Monitoring Strategies

Regular scouting should begin in early spring (March–April in most parts of Texas). Inspect the bark closely, especially in crevices and around pruning cuts. Look for both the white scale coverings and the associated sooty mold.
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To detect crawler activity, double-sided tape can be wrapped around infested branches. The presence of tiny pinkish crawlers on the tape indicates active emergence and signals the optimal timing for certain treatments.

​Management Approaches

An integrated pest management (IPM) approach is essential for effective CMBS control.
Cultural and Mechanical Control:
Light infestations can be managed by physically removing scales using a soft brush or by washing the bark with a strong stream of water. Pruning heavily infested branches can also reduce pest pressure, but care should be taken to properly dispose of infested material.
Chemical Control:
Early-season applications are most effective when targeted at the crawler stage. Contact insecticides (e.g., horticultural oils or insecticidal soaps) can help suppress crawler populations when coverage is thorough.

​These treatments should be applied when temperatures are moderate to avoid plant injury.
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Systemic insecticides, such as those containing dinotefuran or imidacloprid, can provide longer-term control. Soil drenches or trunk applications applied in spring, allow the active ingredient to move within the plant and target feeding scales. However, timing is critical; applications should be made early enough to coincide with active feeding.

Conclusion

Early detection and timely intervention are key to managing crape myrtle bark scale. By combining careful monitoring with targeted cultural and chemical controls, growers and landscape professionals can minimize damage and maintain the health and aesthetic value of crape myrtle plantings throughout the growing season.

Figure: Crape myrtle bark scales on crape myrtle plants (A), Black sooty mold on the leaf and stems on infested crape myrtle plants (B). Photo credit: Rafia Khan