| Missouri Environment and Garden | Volume 8, No. 5 |
| News for Missouri’s Gardens, Yards and Resources | May 2002 |
Powdery mildew of Kentucky bluegrass is most severe on the north side of buildings and other heavily shaded areas. Disease development is also favored by cool, humid, and overcast conditions. Powdery mildew can be easily identified by observing the white, powdery growth on the upper leaf surfaces. Heavy infection causes leaves to turn yellow because the fungus is removing nutrients from epidermal cells. Infected plants are weakened, resulting in thinning of the turfgrass stand.
Powdery mildew is best managed by modifying the environment. Prune trees and shrubs to reduce shade and promote air circulation. Kentucky bluegrass is the least shade tolerant cool season turfgrass, but there are some cultivars that do better in shade than others. In areas with a chronic powdery mildew problem, renovate using one of the more shade tolerant Kentucky bluegrass cultivars or with a fine leaf fescue. Refer to MU Guide G6725, Grasses in Shade: Establishing and Maintaining Lawns in Low Light, for a list of recommended cultivars and general information about growing grasses in shade.
When infection is noted, increase the height of cut. On high profile lawns, a fungicide such as propiconazole (Banner Maxx) or triadimefon (Bayleton) applied at the first sign of disease will reduce further spread.
Barb Corwin, Extension Plant Diagnostic Clinic, UMC (573)882-3019