We have noticed a white powdery accumulation on our flowering crab apple tree (Malus 'Indian Magic').  The tree was planted as part of a complete landscaping two years ago.  It is approximately 8' tall and has vigorous growth this growing season.  The white powdery accumulation is around year-old wood, not on new growth (a photo is attached).  It does not seem to be on leaves.  We talked to a local extension volunteer who thought it was "powdery mildew," but looking on-line that appears to be on leaves, and our problem is not on the leaves.  We would appreciate any guidance.  Thanks.