How to Manage Pests
UC Pest Management Guidelines
Pathogen: Erysiphe graminis
(Reviewed 9/09, updated 9/09, pesticides updated 12/16)
In this Guideline:
DESCRIPTION OF THE DISEASE
Powdery mildew causes grayish white, powdery growth to develop on the leaf surfaces. It begins in isolated patches before spreading over larger areas. In advanced stages of the disease, the leaf blades may turn pale yellow. The fungus survives as small, hardened fruiting bodies (cleistothecia) and may be spread into turfgrass plantings by airborne asexual spores (conidia) from other grasses and hosts.
All turfgrasses are susceptible to powdery mildew, but it is most severe on Kentucky bluegrass and fescues.
CONDITIONS FAVORING DISEASE
Powdery mildew is most injurious in shady areas with high humidity and poor air circulation with temperatures at about 65°F.
In areas that are prone to powdery mildew, plant less susceptible species. The incidence of powdery mildew can be reduced by improving air circulation and reducing shade. Be sure that moisture and fertility are adequate, and raise the mowing height where feasible. Fungicides are generally required only in severe cases.
UC IPM Pest Management Guidelines: Turfgrass
A. Downer, UC Cooperative Extension, Ventura County
Acknowledgment for contributions to Diseases:F. Wong, Plant Pathology, UC Riverside
J. Hartin, UC Cooperative Extension, San Bernardino County
M. E. Grebus, Plant Pathology, UC Riverside