There is a white powdery film on the flower buds and leaves of my crapemyrtle and the flowers dont open normally. Whats the problem, and how can I get rid of it?

It sounds like you have a problem with powdery mildew. Powdery mildew is a fungus disease that is most damaging in dry weather, typically near the end of summer when crapemyrtles are blooming. High humidity, lack of rain, and poor air circulation make powdery mildew worse. Both leaves and flower buds may be affected, but the flower buds often are more severely damaged. All of the Arboretums crapemyrtle introductions have some degree of tolerance for powdery mildew and are rarely damaged enough to warrant fungicide application. Other cultivars may require preventative treatment with any fungicide labeled for powdery mildew beginning when the foliage is fully expanded and continuing at weekly intervals until the flowers open. If youd like a soft alternative to harsh fungicides, you may want to try using horticultural oil on your crapemyrtles since it has been shown to be quite effective in controlling powdery mildew.  more