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UC Pest Management Guidelines

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Turfgrass

Powdery Mildew

Pathogen: Erysiphe graminis

(Reviewed 6/03, updated 6/03)

In this Guideline:

Description of the disease
Susceptible turfgrasses
Conditions favoring disease
Management

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 sexual spores (cleistotheicia) and may be spread into turfgrass plantings by airborne asexual spores (conidia) from other grasses and hosts.

SUSCEPTIBLE TURFGRASSES
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.

MANAGEMENT
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.

Common name Chemical class

Many of these products are available for use by licensed applicators only and cannot be used by home gardeners.

A. AZOXYSTROBIN QoI (strobilurins)

B FENARIMOL DMI

C. MYCLOBUTANIL DMI

D. PROPICONAZOLE DMI

E. THIOPHANATE-METHYL Benzimidazole

F. TRIADIMEFON DMI

G. TRIFLOXYSTROBIN QoI (strobilurins)

PUBLICATION

UC IPM Pest Management Guidelines: Turfgrass
UC ANR Publication 3365-T
Diseases
F. Wong, Plant Pathology, UC Riverside
M. A. Harivandi, UC Cooperative Extension, Alameda Co.
J. Hartin, UC Cooperative Extension, San Bernardino Co.
Acknowledgment for contributions to the disease section:
M. E. Grebus, Plant Pathology, UC Davis

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