How to Manage Pests

UC Pest Management Guidelines

The disease appears as small, circular dead spots (up to several inches in diameter) that have a pinkish color. Often white to pink mycelia are evident in affected areas in the early morning. Small white to pink spore masses (sporodochia) can develop on infected and dead plants. The fungus survives in plants and plant debris as dormant mycelia.

SUSCEPTIBLE TURFGRASSES
Annual bluegrass and creeping bentgrass are very susceptible to this disease.

CONDITIONS FAVORING DISEASE
The pathogen can be active across a broad range of cooler temperatures (32° to 65°F), but air temperatures above 70°F inhibit the growth of the fungus and can shut down the progression of the disease.

MANAGEMENT
Providing good soil aeration and water drainage and reducing shade can discourage the incidence of Microdochium patch. Monitor the evapotranspiration needs of turfgrass to schedule irrigations. Avoid excess nitrogen fertilization, especially in fall and maintain the soil pH between 6.5 and 6.7. High levels of potassium tend to suppress the disease. If Microdochium patch has been a problem in previous years, apply a fungicide in fall before symptoms develop.

Cultural Control
High levels of nitrogen in fall or winter months may increase susceptibility to the fungus, although a nitrogen application in spring after environmental conditions no longer favor Microdochium patch development may aid the recovery of affected areas. High potassium levels may help suppress the disease. Maintain soil pH around 6.5 to 6.7.

Treatment Decisions
In areas where Microdochium patch is chronic, apply fungicides before the advent of cool, wet weather (late fall to early spring), and continue applications until the environmental conditions no longer favor pathogen development. Resistance to dicarboxmide and benzimidazole fungicides has occurred in parts of the United States but has not yet been reported in California.

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.	CHLOROTHALONIL	Chlorophenyl (multi-site)
C.	FENARIMOL	DMI
D.	FLUDIOXONIL	Phenylpyrrole
E.	IPRODIONE	Dicarboximide
F.	MANCOZEB	EDBC (multi-site)
G.	MYCLOBUTANIL	DMI
H.	PCNB	Substituted Aromatic Hydrocarbon
I.	PROPICONAZOLE	DMI
J.	THIOPHANATE-METHYL	Benzimidazole
K.	TRIFLOXYSTROBIN	QoI (strobilurins)
L.	VINCLOZOLIN	Dicarboximide

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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