How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE DISEASE

Microdochium patch is also called Fusarium patch as well as pink snow mold in areas that receive snowfall; the fungus can attack turf underneath the snow cover, causing considerable damage if fungicides are not applied before snowfall. This disease also occurs during periods of cool, wet weather in areas of northern California that receive no snow.

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 inhibits 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		Example trade names	Ag Use R.E.I.+	NonAg Use R.E.I.+
(trade name)			(hours)	(hours)
When choosing a fungicide, consider general properties as well as information relating to environmental impact.
A.	AZOXYSTROBIN	Heritage
	MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)		4	until dry
B.	CHLOROTHALONIL	Daconil
	MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M5)		12	until dry
C.	FENARIMOL	Rubigan
	MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)		12	until dry
D.	FLUDIOXONIL	Medallion
	MODE OF ACTION GROUP NAME (NUMBER1): Phenylpyrrole (12)		12	until dry
E.	IPRODIONE	Chipco 26019
	MODE OF ACTION GROUP NAME (NUMBER1): Dicarboximide (2)		see label	until dry
F.	MANCOZEB	Fore
	MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M3)		24	until dry
	COMMENTS: Dithane M-45 registered for use on sod farms only.
G.	MYCLOBUTANIL	Eagle
	MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)		24	until dry
H.	PCNB	Terrachlor, Turfcide
	MODE OF ACTION GROUP NAME (NUMBER1): Aromatic hydrocarbon (14)		12	—
I.	PROPICONAZOLE	Banner Maxx
	MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)		24	until dry
J.	THIOPHANATE-METHYL	Fungo 50, T-Methyl E-Pro
	MODE OF ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1)		12	until dry
K.	TRIFLOXYSTROBIN	Compass
	MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)		12	until dry
L.	VINCLOZOLIN	Curalan, Touche
	MODE OF ACTION GROUP NAME (NUMBER1): Dicarboximide (2)		5 days	until dry
1	Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions (for more information, see http://www.frac.info/). Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action Group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode of action Group number; for fungicides with other Group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action Group number.
+	Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Agricultural use applies to sod farms and commercial seed production.
—	Indicates use is not listed on label.

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 County
Acknowledgment for contributions to Diseases:
J. Hartin, UC Cooperative Extension, San Bernardino County
M. E. Grebus, Plant Pathology, UC Riverside

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