Answer: Poinsettia leaves are very sensitive to foliar sprays so I'd suggest pinching off the affected leaves rather than trying to spray to control a problem. There are a number of diseases that can cause spots on the leaves. White spots can be powdery mildew which indicates air circulation is poor and the plant is experiencing warm days and cool nights. I'd simply pinch off the affected leaves to keep the problem from spreading.
Best wishes with your poinsettias!
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