Agriculture and Natural Resources Blog

Matthew Orwat
County Extension Agent – AG/NR
Email: matthew.orwat@ag.tamu.edu

Treating Crape Myrtle Scale

Article written by Master Gardener Volunteer Stephanie Suesan Smith for the Agriculture and Natural Resources division.
August 4, 2025

Crape myrtles (Lagerstroemia) are very pretty and versatile trees.  They come in a range of sizes from a few feet tall to forty feet.  The blooms range from light pink to bright pink.  Crape myrtles are not native to Dallas but have been planted so widely they are often encountered in the landscape.  However, they have been having trouble with crape myrtle scale in the last decade or so.

What is Crape Myrtle Scale?

Crape myrtle bark scale (Acanthococcus lagerstroemiae, CMBS) is an Asian pest that was first noticed in the Dallas area in 2004.  By 2016, it was seen in eleven states.  Researchers across the southern United States have created a website on CMBS, but it has not been updated since 2020, when Dr. Mike Merchant retired from Texas A&M AgriLife Extension. 

Crape Myrtle Struggling with Crape Myrtle Scale Photo courtesy of Stephanie Suesan Smith ©2019

Crape Myrtle Struggling with Crape Myrtle Scale Photo courtesy of Stephanie Suesan Smith ©2019

Symptoms of Crape Myrtle Scale

CMBS are related to other scale insects.  I noticed my crape myrtle was struggling in 2019 and asked Dr. Merchant for help.  The symptoms were white scale on the wood, sooty mold which grows on the sugary excrement of the scale, and a general decline in the health of the tree.  The sooty mold turns the trunk and branches black.  The flowers and leaves had sooty mold on them, too.  This reduces the blooms and can keep the tree from photosynthesizing because the mold blocks the light.

Treating Crape Myrtle Scale

Dr. Merchant made a video of how to treat CMBS.  It is a good video, and I used it to treat my tree.

First, you get a bucket and put a couple of gallons of water in it.  Give it a squirt of dishwashing soap.  You want the water to be very soapy.  Take a soft bristle brush and scrub the sooty mold off the tree trunk and branches.  Don’t worry if some bark comes off.  Crape myrtles shed bark all the time.  Get the soap in the crevices and cracks of the tree.

Next, you need to hose down the tree to get the soap and mold off of the crape myrtle.  You may have to scrub more mold that was hiding under the dirty water.  Repeat until the tree is as clean as you can make it.

Finally, you will need to apply a systemic insecticide to the soil around the trunk of the crape myrtle.  These insecticides have active ingredients of one or several of these choices:  imidacloprid, imidacloprid + clothianidin, dinotefuran, and thiamethoxam.  The one Dr. Merchant used is Bayer Advanced 12 Month Tree & Shrub Insect Control II Landscape Formula.  The name has changed to Bio Advanced 12 Month Tree & Shrub Insect Control Landscape Formula.  These products are very expensive but kill scale and other insects that bite into the bark, leaves, and flowers for a year.

Use long dishwashing gloves to completely cover your arm up to your elbow.  If you have safety glasses, wear them as well.  You do not want to get this stuff on you or in your eyes.  Keep pets and humans, especially children, away from the treated tree until the area is no longer wet. 

You must follow the precautions on the label of the product you are using.  You will also need to measure the height of the tree to the nearest foot.  To legally treat the crape myrtle tree, it cannot have blooms on it.  These products can possibly harm bees.  If your crape myrtle is in bloom, wait until the blooms stop to treat the tree.

Mix the solution according to the label with three or four gallons of water.  Pour the mixture around the trunk of the crape myrtle.  Do not get the solution on the tree.  If it has just rained, wait until the soil dries out so the tree will immediately absorb the poison.  Wait to water the area around the crape myrtle until the insecticide has soaked into the soil, about 24 hours.  Once the mixture travels from the roots to the rest of the tree, the scales will die.  You may have to scrub the tree again to get the dead scale insects and any remaining sooty mold off. 

My crape myrtle survived the attack by CMBS pests and recovered after I followed the treatment described in this article.  If you are not sure what is attacking your tree, take good, sharp, close-up photos of the pest and a picture of the whole tree and send them to the Dallas Master Gardener’s Help Desk at dallasmg@ag.tamu.edu for identification.