A: That is crape myrtle bark scale, and you do need to treat it. This pest sucks sap from the plant, making it less vigorous and reducing bloom. Sticky residue from the insect can coat branches, stems, and leaves, then airborne molds may grow in the sugary material and blacken the trunks of the plant.
Your tree isn’t in danger of dying, but it can become very unattractive. Plants which are under stress (grown in partial shade, new, damaged in some way, badly pruned) are the most susceptible, but even healthy plants can get a touch of this pest. The insect gets into every nook, cranny, and crevice of the branch structure and thus it’s hard to spray for.
The good news is that it is very easy to treat with a drench insecticide. We recommend our Bonide or Ferti-lome Systemic Insect Drench. Mix in water according to label instructions, and pour the drench slowly around the base of the crape myrtle trunk. The pesticide will have to travel up the trunks and branches, so give the product some time to work – typically two to three weeks. Then the scales will start dying, and the plant will be protected from re-infestation for the rest of the season. Keep an eye on the plant in the late fall and next spring to see if any further treatment is necessary.
If you haven’t already done so this spring, feed your crape myrtle and all your shrubs and trees now. We recommend our Covington’s Tree & Shrub Fertilizer.
Burton specializes in diagnosing and solving plant problems. If you have a question for Burton, please email him at burton@covingtonnursery.com and include photos showing the problem.