Crape Myrtle Bark Scale in the DMV
Written by: Vira Sisolak, UDC Master Gardener & Mary Blakeslee, FONA Member
A new scale pest of crape myrtle called Acanthococcus lagerstroemiae (Common Name: crape myrtle bark scale) has made its way from Texas through the southeastern United States and is now threatening the use and appearance of crape myrtles in Washington, DC. The crape myrtle bark scale (CMBS) introduced in Texas in 2004 from Asia lives and thrives on crape myrtle. A DC Master Gardener observed this pest in a public space garden on Capitol Hill and the diagnosis was made by a DC Urban Forestry Division arborist in November 2021.
CMBS produce copious amounts of a sugary waste known as honeydew. As a result, the leaves, branches, and trunk become covered with black sooty mold, which grows on the honeydew. These infestations appear as white or gray, waxy crustations on stems, large twigs, and trunks, but rarely on foliage. They congregate in branch crotches and at pruning sites.
This scale will settle to feed under loose, exfoliating bark of the crape myrtle, which makes control by both predators and pesticides more difficult. The end result is a crape myrtle that is black and ugly (due to heavy sooty mold accumulation) and produces fewer and smaller blooms. Untreated, crape myrtles that are heavily infested with CMBS become a landscape eyesore.
Effective treatments are available but most must be applied by a licensed pesticide applicator. They are relatively costly and do not provide 100% control, meaning that treatments must be reapplied each year.
On the local front, the DC Division of Urban Forestry is already taking action to ensure it can maintain the city’s crape myrtles and change its planting and pruning activities to reduce further spread of CMBS. Their first step has been to learn about this invasive species new to the District. They are also in contact with colleagues in surrounding municipalities to inquire about their experience and observations. Lastly, they are developing a management plan to address planting of crape myrtles, inspections for CMBS, sanitation methods, control methods, and guidance for the general public. They will share this information when it is available on their forest health website.
For now, additional information about this pest and treatments can be found on the following websites:
