CRAPEMYRTLE BARK SCALE

Photo Captions

Bottom Left–

Adult Female

Scale on Crape

Myrtle branch

Bottom Right–

Up close view of

adult CMBS

Top Right– Ex-

ample of Black

Sooty Mold

Jim Robbins University of Arkansas

New Pest Threatens Crapemyrtle

An invasive pest has been identified on crapemyrtles in the Jackson Madison County area. It is

known as Crapemyrtle Bark Scale (CMBS). This relatively new pest was first noticed in Dallas

TX several years ago and has recently been working its way eastwardly across the state of TN.

Shelby County was the first area in TN to identify this pest and begin control measures.

Although an unchecked infestation may not kill otherwise healthy crapemyrtles, the pest stress-

es the plant, affecting not only its appearance but also interfering with blooming and overall

thriftiness. It is the only bark scale to occur on crapemyrtles at this time and should be easy to

identify. Adult females appear as white or gray felt-like encrustations on small twigs to large

trunks, often near pruning wounds or branch crotches. Most gardeners will be alerted to its

presence by the black sooty mold on the bark (not to be confused with sooty mold associated

with aphid feeding).

Tips for Control and Reducing Spread

University researchers are very concerned about the difficulty of control. Faculty of the Univer-

sity of TN Soil, Plant and Pest Center in Nashville are preparing public information materials. In

the meantime, current best practices for control include the following:

Check for signs of CMBS and the presence of black sooty mold routinely

Wash the trunk and reachable limbs with a soft brush and a mild solution of dish

washing soap. This will remove many of the scale and egg masses, much of the

black mold, and increase the effectiveness of insecticide control.

A winter application of dormant oil to the bark may be helpful. However, thorough

coverage is necessary for positive results.

During the growing season, drenching the root zone with a systemic insecticide has

shown promise with best control when applied between May and July. Neonicotinoid

insecticides like Imidacloprid have demonstrated good control. There has been

some controversy on the use of Neonicotinoids and their impact on the environ-

ment. However, crapemyrtles are a valuable plant in the southern landscape and you

may wish to ensure their persistence.

Mengmeng Gu, Texas A&M Extension Service

Gary Brooks Bayer Crop Science

Be on the outlook for crapemyrtle bark scale (CMBS) on your crapemyrtles. CMBS is an insect that made its way to west TN in 2013. It has been widespread in Memphis for some time but was first found in North West Jackson in late summer of 2015. It has rapidly spread through many of the North Jackson subdivisions. In the fall of 2016, it was found in the Lambuth area of Jackson and a few locations in the Nashville. It is in at least 11 other states, and eventually all crapemyrtles in the U.S. will come in contact with this invasive pest. Often the first sign of CMBS is a black substance that appears on the trunk and leaves. This black film is known as sooty mold. It is fungus that grows on insect excretions (poop). Once the insect has died and the mold has nothing to feed on it will wash off with time, or can be scrubbed off with a hose and soft brush. With CMBS, on closer inspection you will easily see the scale insect which will appear as a light gray, almost white felty scale about a tenth of an inch long. It will exude a pinkish liquid if punctured or squished. This is what differentiates the CMBS from the more common and less damaging forms of sooty mold which can appear on crapemyrtle caused by less harmful pests like aphids. In general, scale insects are one of the more difficult pests to control due to their waxy outer coating, which prevents spray treatment from penetrating their bodies. Soil applied systemic insecticides are the most effective treatments currently available for CMBS and the easiest to apply. Insecticides containing the active ingredient imidacloprid applied at the base of the plant as new growth begins to appear will provide 12 month control. This is typically in late April to early May but can be applied in June and July if needed. If CMBS is active in your area, a preventative yearly treatment will also protect the crapemyrtles that have not yet been infected. Fertilome Tree and Shrub Systemic Drench and Bayer Advanced Tree and Shrub Insect Control II are just two of the many products that contain imidacloprid and are available to homeowners. Just like with medication, the active ingredient (imidacloprid) can be found in name brands as well as generic brands. They are both effective, but be conscious of the percentage of active ingredient to ensure that you are comparing apples to apples. Some products contain fertilizer as well. I would avoid those. No need to pay extra for overpriced and unnecessary fertilizer. Always read and follow label directions for any pesticide. A final thought, even though CMBS will not kill the plant, but makes it unsightly and is then the "typhoid Mary" of the neighborhood. If you are not willing to treat the pest, removing infected specimens would be the most responsible action to take in order to prevent the further spread of this pest. Here are a few helpful links. https://extension.msstate.edu/sites/default/files/publications/publications/p2938.pdf https://www.uaex.edu/publications/pdf/fsa-7086.pdf If you have further questions contact your local county Extension agent.