Both of my Hydrangea's and a rose is severely infected with powdery mildew....
Both of my Hydrangea's and a rose is severely infected with powdery mildew. Will our harsh winters kill the problem so next spring it won't come back?
Johnson County Missouri
Unfortunately, our cold winters will not kill powdery mildew. This fall pick up infected leaves and blooms and dispose of them. If we get a lot of rain next spring and summer and temperatures remain cool like this summer, powdery mildew will be a problem again. Use a fungicide to prevent the spread of powdery mildew. Also, good air circulation helps.