This article covers the topic of controling Crepe Myrtle (also spelled Crepemyrtle, Crapemyrtle or Crape Myrtle) bark scale.
There is a new serious threat to one of our favorite trees; even more serious than the unsightly and oft mentioned crape murder. As a reminder, crape murder is the extreme pruning of crapemyrtles that results in weakened and deformed trees. Prune correctly, y’all! Okay, jumping off that soapbox, let’s talk about the Crapemyrtle Bark Scale. It has been around the Southeast for years but this insect showed its’ destructive little head in Arkansas earlier this year…and it occurred in West Little Rock! Are we gonna just take this or are we gonna fight? We say fight!
*Pictures of Crapemyrtle Bark Scale were provided by the University of Arkansas Cooperative Extension Service.
Crapemyrtle Bark Scale (let’s call it CMBS) is a small insect that appears as a white or gray felt-like encrustation. CMBS might be found anywhere on crapemyrtles, and often appears near pruning sites and branch crotches of more mature wood. Often times, the first sign of CMBS is the black sooty mold on the tree bark. This may be misleading since a more common and easier to control pest, aphids, can also cause sooty mold. A close inspection will determine which pest is present.
This tree is heavily infested with CMBS; notice the gray and white insects all over and the black sooty mold covering the entire surface of the tree bark.
As with most insects, there are several life stages and the appearance of CMBS changes with the stages. CMBS might be able to overwinter in the adult female and egg life stages, and crawlers and later stage nymphs have been observed overwintering under the loose bark and in cracks and crevices of crapemyrtles in our area. In one year, there could be at least two generations of CMBS. This can be a difficult pest to control and it may take multiple years of treatment. So, how do we fight this pest? Keep reading!
Again, black sooty mold with gray and white specs being CMBS.
Treatment – The best window for control is late April or early May as the crapemyrtles begin to really flush; during this window, apply a soil drench of an imidacloprid product such as Ferti-Lome Tree & Shrub Systemic Insect Drench. If CMBS are in your area, it would be a good idea to apply this as a preventative measure during this window. This imidacloprid product is a soil drench that is watered into the root zone, specifically in the drip line of the tree where the feeder roots are located. Every month past May, the effectiveness of control decreases since the plants are growing less and less. During times when crapemyrtle trees are not in leaf, apply sprays of dormant oil (containing paraffin oil) or permethrin, taking care to apply under loose bark and in cracks and crevices.
*We have had a lot of questions lately and wanted to make this as clear as possible! Here is the list of what you can do and when it needs to be done:
Mix dishwashing soap with water and scrub the branches with a soft bristle brush.
Late Fall-Early Spring
Once the tree defoliates or before it puts on new foliage, spray with a dormant oil. This can be done multiple times. Apply thoroughly, making sure to get the product under crevices in the bark and between branches.
Late April-Early May
Apply Ferti-Lome Tree & Shrub Systemic Insect Drench. This is a soil drench; just mix correctly with water and apply in a band along the drip line of the plant. To measure the crapemyrtle, add up the circumference of all trunks at chest high (about 4.5 feet off the ground). For example, if you have 5 trunks and the trunk circumference is 4 inches each, then you have a total of 20 inches in circumference. The drench will need to be applied to the drip line of the plant. The drip line of the plant is considered to be the outer circumference of the plant branches and inward toward the trunk several feet (see diagram above). In order to apply this 20 ounces properly, it will need to be mixed into several gallons of water so that there is enough volume to be applied in a 3-4 foot band from the drip line in towards the tree trunk all the way around the plant.
Late Summer-Early Fall
Treat with Hi-Yield Systemic Insect Spray using a hose end sprayer. This should be done after blooming has ended for the season. Be sure to coat the trunk and leaves thoroughly.
For more information, visit the University of Arkansas Cooperative Extension Service fact sheet. We thank them for providing the images! The Good Earth Garden Center has what you need to save your crapemyrtles….come see us!