May 26, 2020
"Yikes! My beautiful Crape Myrtles have black mildew all over the branches and leaves. They also have some weird white spots."
This is a common issue we hear when people call us in regards to their Crape Myrtles. We know now that it is Crape Myrtle Bark Scale.
What is Crape Myrtle Bark Scale?
After much research, we learned that CMBS is actually an insect. This insect (called a “scale”) was originally found in Richardson, Texas in 2004 and has slowly been spreading through neighboring states, including Oklahoma and Arkansas. It was found in Oklahoma County in 2015. Irish Green found and reported the first case of Crape Myrtle Bark Scale in Cleveland County August 2016 (confirmed by Plant Disease and Insect Diagnostic Laboratory at Oklahoma State University).
One of the first signs of this insect is black sooty mold on the bark and leaves. Bark and leaves may feel sticky to the touch as a byproduct of where the scale is feeding. The "white spots" look similar to felt and are usually located in the branch crotch or pruning wounds; but can be found anywhere on bush/tree.
How Can We Help?
GOOD NEWS - We can treat this scale and your beautiful crape myrtles shouldn't die. Crape Myrtle Bark Scale is not easily controlled so you will need to faithfully apply 2 insecticide treatments, one in Spring once crape myrtles break out of dormancy and leaves begin to appear (happening right now). The second in Fall, once the trees/bushes have dropped their blooms. If you would like, we can take care of these applications for you.
Current management recommendations from the Oklahoma State University Extension include the following:
- Carefully inspect crape myrtles prior to purchase for signs and symptoms of CMS, including the presence of white to gray scale bodies on bark, honeydew and/or black sooty mold. Always buy plants that are free of mechanical damage, such as bark wounds that may serve as "points of entry" for CMS
- The bark of infested plants can be scrubbed with a soft brush and a mild solution of dishwashing soap and water. Washing removes many of the female scales and egg masses, possibly improving insecticide effectiveness, as well as buildup of black sooty mold on branches and trunks. (The soot and scales will come back. From my research, this is not always practical and, therefore, optional.)
- Horticultural oil may be applied during the winter at a dormant oil rate. Ensure adequate coverge of the entire tree and use enough oil to reach behind those loose bark, branch crotches, and other crevices. (From my research, this is optional also. But if possible, personally, I would try it. We can do this for you also.)
- Systemic insecticides provide the best chemical control option in efficacy trials to date.
OUR SPECIFIC PLAN FOR CRAPE MYRTLES:
Irish Green Lawn Care’s recommendation is to apply one insecticide in the Spring and one in the Fall. Allow the material several weeks to move into all plant tissues. We can do this for you.
IRISH GREEN’S Complete TREE AND SHRUB PROGRAM
As you're probably already aware, trees and shrubs have always been of special interest to us; therefore, we have had a tree and shrub program for 10+ years. At Irish Green, we have a 5 application tree and shrub program that results in noticeable differences. We strongly believe that fertilizer, insecticides, and fungicides are all needed. Our 5 application program includes your 2 insecticide applications discussed above, plant probiotics, organic components, fertilizer applications, fungicide applications; everything you need to ensure a beautiful healthy landscape. Since including our new plant probiotics and organics into the mix, I have seen a noticeable difference in all my trees and bushes.
This is a picture ( Spring 2017) of one of my pine trees after just 2-3 applications.
Please email, chat with us from our website, or call our office as soon as you see the black soot and/or white scales. My recommendation is to treat your crape myrtles now as a preventative, as it is very hard to control once you get them.
If you have any additional questions or would like to get a quote or scheduled for our tree and shrub program, please contact us through email or give us a call.
Safer. Better. Greener.
Gu, M., M. Merchant, J. Robbins, and J. Hopkins. 2014. EHT-049: Crapemyrtle Bark Scale, A New Exotic Pest. Texas A&M AgriLife Extension at http://www.eddmaps.org/cmbs/Resources/TAMUCrapemrytlebarkscaleEHT-049.pdf
Merchant, M. 2014. Crapemyrtle Bark Scale Reduces Bloom. Insects in the City blog. Texas A&M AgriLife Extension at: http://citybugs.tamu.edu/2014/08/14/crapemyrtle-bark-scale-reduces-bloom
Rebek, E.J. 2015. CR-7092: Management of Insects and Mites in Tree Nurseries. Oklahoma Cooperative Extension Service at http://http://entoplp.okstate.edu/pddl/pddl/2015/PA14-39.pdf
Mar 28, 2020