How to Manage Pests

UC Pest Management Guidelines

Turfgrass

Microdochium Patch (Fusarium Patch, Pink Snow Mold)

Pathogen: Microdochium nivale

(Reviewed 9/09, updated 9/09, pesticides updated 12/16)

In this Guideline:


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 dicarboximide and benzimidazole fungicides has occurred in parts of the United States but has not yet been reported in California.

Common name Amount to use Ag Use
REI‡
NonAg Use
PHI‡
(Example trade name)   (hours) (days)

UPDATED: 12/16
Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
When choosing a pesticide, consider its usefulness in an IPM program by reviewing the pesticide's properties, efficacy, application timing, and information relating to resistance management, honey bees (PDF), and environmental impact. Not all registered pesticides are listed. Always read the label of the product being used.
 
A. AZOXYSTROBIN
  (Heritage) Label rates 4 Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
 
B. CHLOROTHALONIL
  (Daconil Action) Label rates 12 Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M5)
 
C. FLUDIOXONIL
  (Medallion) 0.25–0.5 oz/1000 sq ft 12 Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Phenylpyrrole (12)
 
D. IPRODIONE
  (Chipco 26019) 4–8 fl oz/1000 sq ft. See label Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Dicarboximide (2)
 
E. MANCOZEB
  (Fore 80WP) Label rates 24 Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M3)
  COMMENTS: Dithane M-45 registered for use on sod farms only.
 
F. MYCLOBUTANIL
  (Eagle 20EW) 1.2–2.4 fl oz/1000 sq ft 24 Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
 
G. PCNB
  (Turfcide 400) Label rates 12
  MODE-OF-ACTION GROUP NAME (NUMBER1): Aromatic hydrocarbon (14)
 
H. PROPICONAZOLE
  (Banner Maxx) 2–4 fl oz/1000 sq ft 12 Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
 
I. THIOPHANATE-METHYL
  (Fungo Flo) Label rates 12 Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1)
 
J. TRIFLOXYSTROBIN
  (Compass) Label rates 12 Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
 
K. VINCLOZOLIN
  (Curalan EG, Touche EG 2.7 lb/acre (1 oz/1000 sq ft) 120 (5 days) Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Dicarboximide (2)
 
1 Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions. 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 (REI) 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.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Turfgrass
UC ANR Publication 3365-T

Diseases

A. Downer, UC Cooperative Extension, Ventura County
M. A. Harivandi, UC Cooperative Extension, Alameda 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

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