Answer: Crape myrtles bloom on new growth so pruning in the spring will help it develop lots of new, flowering stems. The insects sound like they are feeding on the fluids from the leaves of the plants. As they feed they exude a sticky substance called honeydew which is high in sugar content. This is probably what is attracting the wasps and hornets. If you get rid of the insects, the wasps and hornets will stop visiting. The white substance is powdery mildew, a fungal disease. Some cultivars of crape myrtle are more susceptible to this than others. You can prune away the diseased parts of your crape myrtle, which will also get rid of the insects, or you can spray with a fungicide. These include: sulfur, neem oil (Rose Defense, Shield-All, Triact), triforine (Ortho Funginex), or potassium bicarbonate (Kaligreen, First Step). If you spray with a product such as Rose Defense which is neem oil based, the neem oil will also control the insect pests. Good luck with your crape myrtle!
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