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It seems like I remember you talking about how to treat for Crapemyrtle Bark Scale but can you refresh my memory? AT

Crapemyrtle bark scale is an ongoing problem for area crapemyrtles and now is a great time to take action to rid your crapemyrtles of this pest.

Crapemyrtle bark scale is exactly what it says it is - a scale insect that feeds on crapemyrtles. Scale insects can be difficult to treat since their hard scale protects them from many pesticides. Because of this, we must take another approach.

CMBS (crapemyrtle bark scale) insects have what are called piercing/sucking mouth party. With these mouth parts, they are able to pierce the bark of the plant and extract nutrients. A small quantity of CMBS insects is not an issue. The problem is that there won’t be a small quantity for long.

Female CMBS insects can lay between 60 to 250 eggs. These eggs overwinter underneath the scale and begin to hatch between April and May. When they emerge they are very small and a light pink in color. They move from plant to plant by hitching rides on birds or letting the wind blow them to nearby plants. There is a second generation in the late summer.

The first indicator that your crapemyrtle has CMBS insects is usually when you notice some of the plant’s leaves are covered in something black. This is a black fungus called black sooty mold. The mold grows on the excretions of the CMBS insects which is called honeydew. Ants love this sweet substance so you might also notice an abundance of ants moving up and down your crapemyrtle.

The best way to deal with CMBS insects is a dormant oil treatment while the crapemyrtle is dormant during the winter on days where the temperature is over 50 degrees. Dormant oil is a horticultural oil that is thicker in consistency. Because of this thickness it is not appropriate to use during the growing season as it might damage the plant by smothering it. But smothering is exactly what you want to do to the CMBS insects. Dormant oil is available at most garden centers.

To treat, just pick a time during the winter where we are in a bit of a warm stretch and soak the plant with dormant oil. This should help to minimize the issue if not eliminate it completely.

You may see other recommendation to treat for CMBS using a pesticide called Imidacloprid. Imidacloprid is considered a systemic pesticide which means that you mix it with water and pour it into the root zone, allowing it to be absorbed into the plant and thereby attacking the insect from the inside. In theory the CMBS insects would ingest the pesticide while feeding on the plant. However, because crapemyrtles are a flowering shrub, insects visiting the flowers can become collateral damage. Because of this, we do not recommend using imidacloprid to treat for CMBS. 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: Jim Robbins, Univ. of Ark. CES, Bugwood.org