Answer: What you describe sounds like a fungal disease called powdery mildew. To reduce additional infections, avoid overhead watering to help reduce the relative humidity. An application of a fungicide may be necessary. These include: sulfur, neem oil (Rose Defense, Shield-All, Triact), triforine (Ortho Funginex), or potassium bicarbonate (Kaligreen, First Step). Be sure to apply according to label directions. Good luck with your crepe myrtle!
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