We don’t seem to hear as much about it these days, but crapemyrtle bark scale is still out there and still wreaking havoc on our crapemyrtles. Fortunately, the name on this one is exactly what it is. It’s a scale insect that attaches to the bark of a crapemyrtle.

If you have a crapemyrtle in your landscape, now would be a good time to check on them to see if there are signs of this bark scale. You’ll need to look at the branches to see if there are any brown or white bumps, likely clustered close to one another. Or, you may have bark on your crapemyrtle that is black which is not the normal color for bark on a crapemyrtle.

If you see some of these brown or white bumps, these are the protective covers that keep the scale insect safe underneath. The presence of this covering makes treating for this disease a little more problematic, but not impossible.

Protected underneath that covering is an insect with what we call piercing/sucking mouth parts. As they live under the hard shell, they are free to feed upon your plant. A few of these insects is not a problem, but if they have time to increase in quantity, they can be detrimental to the health and beauty of the plant.

The female scale insects can lay between 60 to 250 eggs with these eggs overwintering under the hard shell to hatch sometime between April and May. The insect that emerges is very small and light pink in color. At this point they can move around the plant or move to other plants via a bird or the wind. Most years, there is a second generation later in the summer.

During the summer, the first sign you may have a problem with crapemyrtle bark scale is that you might notice some of its leaves covered in a black substance. This is a black fungus that grows on the excrement of the scale insect. Their excrement has a very pleasant name - honeydew. You might also notice a higher-than-normal presence of ants since ants are attracted to this apparently delicious honeydew.

The best way to treat for crapemyrtle bark scale is to spray the shrub/tree with dormant oil on a day when it’s over 50 degrees outside but while the plant is still dormant. Dormant oil is a horticultural oil that is thicker and only meant to be sprayed on dormant plants. It can damage healthy, green plants during the growing season, but you are good to go when the plant is dormant. This oil smothers the scale insect underneath that hard shell.

You might see a pesticide called Imidacloprid recommended to treat crapemyrtle bark scale, but this one comes with some challenges. Imidacloprid is a systemic pesticide, which means it should be mixed with water and poured on the root growing zone of the plant. It works when the plant draws the insecticide up inside the plant, killing the scale insect from the inside. The problem is that Imidacloprid is not picky about its target, so when it makes its way into the flowers, the visiting pollinating insects will unfortunately become collateral damage. Because of that, we do not recommend Imidacloprid for the treatment of crapemyrtle bark scale. So, get some dormant oil and a pump sprayer so you can be ready for a day when the temps are in the 50s. Good luck!

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at mg@tulsamastergardeners.org. Photo: Tom Ingram