The veins stay green while the rest of the leaf dies. This is a delayed response to cold weather. If they are not severely affected they should recover. There is no treatment. Some plants look like they were sprinkled with sugar or powder.
New growth is twisted and white, especially on dogwoods and crape myrtles.
This is powdery mildew. The disease really stands out, as easy to identify as rainbow sherbet . It generally does little damage. I would try to ignore it. Control it by planting resistant crape myrtle varieties or spraying with a fungicide as needed.