Troubleshooting a really big hurting crepe myrtle - Ask Extension
We have a really big crepe myrtle that hasn't produced many flowers the last 2 years and has stained our new porch roof. We noticed sticky stuff on ev...
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Troubleshooting a really big hurting crepe myrtle #885404
Asked September 16, 2024, 11:21 AM EDT
We have a really big crepe myrtle that hasn't produced many flowers the last 2 years and has stained our new porch roof. We noticed sticky stuff on everything below it and it has attracted lots of bees and European hornets this summer. We just noticed this weekend that there are white things all over it and the leaves are starting to turn black. Not sure how long this has been going on, and hadn't specifically looked at the leaves, etc for any signs. Googling the symptoms I expect it's bark scale, but wanted to confirm and figure out how to handle it. I read suggestions about pressure washing the tree, but as you can see it's not really feasible on this big of a tree. Can someone help identify the problem and suggest correct actions, please?
Thanks in advance, Ron
Calvert County Maryland
Expert Response
Hello Ron,
We agree that those white insects pictured on the bark are Crapemyrtle Bark Scale, though honeydew (the sticky clear residue) and sooty mold (the black fungus growing on the honeydew) can also be associated with Crapemyrtle Aphids, and it's possible the two insects overlapped in presence earlier this year. Management options for scale are included on our general scale web page, and most treatment types used for scale will probably reduce aphid populations as well, if they are present.
If a systemic insecticide is needed, or even a non-systemic that needs to be sprayed on the bark, hiring a certified pesticide applicator is either required (for certain chemicals) or advisable, as they will have better-calibrated equipment to make applications and should be familiar with how to treat scale insects by looking for when crawlers are active, since they are the life stage most vulnerable to pesticide intervention. A full year or more of treatment might be needed before a high population of scale is brought under control. As noted on the page linked above, sometimes predators of the scale suppress their numbers on their own, though they usually cannot eradicate a scale population on their own that has already become established. We do not have a list of certified pesticide applicators (the agency that certifies them, the MDA, does, but it's not a very user-friendly page), but most landscaping companies do have them on staff, and many arborists or licensed tree experts also hold that certification.
Miri
We agree that those white insects pictured on the bark are Crapemyrtle Bark Scale, though honeydew (the sticky clear residue) and sooty mold (the black fungus growing on the honeydew) can also be associated with Crapemyrtle Aphids, and it's possible the two insects overlapped in presence earlier this year. Management options for scale are included on our general scale web page, and most treatment types used for scale will probably reduce aphid populations as well, if they are present.
If a systemic insecticide is needed, or even a non-systemic that needs to be sprayed on the bark, hiring a certified pesticide applicator is either required (for certain chemicals) or advisable, as they will have better-calibrated equipment to make applications and should be familiar with how to treat scale insects by looking for when crawlers are active, since they are the life stage most vulnerable to pesticide intervention. A full year or more of treatment might be needed before a high population of scale is brought under control. As noted on the page linked above, sometimes predators of the scale suppress their numbers on their own, though they usually cannot eradicate a scale population on their own that has already become established. We do not have a list of certified pesticide applicators (the agency that certifies them, the MDA, does, but it's not a very user-friendly page), but most landscaping companies do have them on staff, and many arborists or licensed tree experts also hold that certification.
Miri
