If your plants' leaves have a white or gray dust on them, powdery mildew is probably attacking your garden. It's a common disease, and different strains of powdery mildew attack a wide range of plants.

Powdery mildew spores can overwinter in your garden -- so remove all affected fallen leaves from your garden during and at the end of the season. If you see leaves that are just beginning to show the disease, pluck them off the plant and throw them away to help keep powdery mildew from spreading to healthy plants.

Powdery mildew loves still, humid conditions, so keep spaces between your plants for air to flow through. Divide perennials every few years to keep them loose and open and prune trees and shrubs so they don't get too thick. Also: Consider airflow when you choose spots for your plants. Avoid planting mildew-prone plants in especially sheltered spots.

Fungicides can effectively stop powdery mildew from spreading, but they're not as good at killing the disease once it's established. So use fungicides -- either traditional or organic -- in wet, humid periods before you see a problem or just as the plants first start to show symptoms. Look for these products at your local garden center, nursery, or online.

Some plants have been bred to resist the disease better than others. While they can certainly suffer from the disease, powdery mildew tends to affect them less than on mildew-prone varieties. Here are some top-performing mildew-resistant varieties:

Adirondack crabapple

Aurora dogwood

Blue Stocking bee balm

Bonica rose

Cherokee Brave dogwood

David phlox

Donald Wyman crabapple

Hopi crape myrtle

Iceberg rose

James McFarlane lilac

Marshall's Delight bee balm

Miss Kim lilac

Natascha phlox

Natchez crape myrtle

Olympiad rose

Prairifire crab apple

Profusion zinnias

Sexy Rexy rose

Sheer Bliss rose

Topaz Jewel rose

Violet Queen bee balm

Zahara zinnias