Question
I am new to the KC area, to the midwest.  What I believe is powerdery mildew has taken over my garden. It has killed shrubs and perennials.  How can I best get rid of it?  

Answer
Hi James,
Thanx for your question.  I'm in KC too.  One of the best ways to control powdery mildew is improving sanitation.  Prune shrubs and woody perennials removing all dead or unkempt growth.  Clean around the drip line of plants removing unnecessary vegetation.  If plants are growing to closely, thin them out for good air circulation.  Use plants that are not prone to the disease.  Do not spray water on top of plants but water at ground level.  Avoid too much shade for sun-loving plants.  Here is some additional information from Ohio State University.  I hope this helps.
Tom

http://ohioline.osu.edu/hyg-fact/3000/3047.html