Answer: Unfortunately, based on your description it sounds as though one is suffering from powdery mildew and the other is showing early signs of cedar apple rust infection. While some varieties are tolerant of the mildew, the cedar apple rust is generally fairly serious. You might wish to take samples to your County Extension office for positive identification of the problems and suggested control recommendations, if any.
Apples are susceptible to a wide range of diseases, so many home orchardists find it worthwhile to follow a routine preventive spray schedule based on both the particular apple varieties they are growing and on the diseases most prevalent in their local vicinity; the weather during any given year can also make a difference in the optimum spray routine and schedule. The County Extension staff should also be able to provide you with current spray guidelines for apples grown in your area and help you determine a schedule suitable for your trees.
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