Answer: I wish I could diagnose the problem with your oak tree but without being able to inspect the problem areas, I'd just be guessing. Powdery mildew can attack the tips of the stems, but so can an insect pest called the oak twig girdler. To complicate matters, other insects and diseases can cause simlar symptoms. Rather than guess, I'd suggest taking samples of the affected leaves and stems to your cooperative extension office for microscopic exam and identification. Helpful folks there can recommend control measures. Contact LSU Cooperative Extension Service, 1 University Pl, Shreveport, LA 71115-2301 phone (318) 797-5137?.
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