Turffiles:Diseases:Microdochium Patch

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Microdochium Patch (Pink Snow Mold)

[Microdochium nivale]

SYMPTOMS

Pink snow mold develops during periods of snow cover, with symptoms of the disease becoming evident as the snow melts. The disease appears in roughly circular patches from 2 inches to 1 foot in diameter that are white or light tan in color. A ring of salmon or pink-colored growth is present on the outer edge of patches when the disease is actively developing. The infected leaves within the patches are usually collapsed and matted down upon themselves.

Microdochium nivale may also infect turfgrasses in the absence of snow cover during periods of cool, wet weather; in these cases, the disease is referred to as Microdochium patch. The symptoms of Microdochium patch are slightly different than pink snow mold. The patches are similar to pink snow mold in size and shape, but are reddish-brown or salmon-colored and greasy in appearance. When the disease is actively developing, the patches may be surrounded by a dark brown or bronze ring.

Microdochium patch

Characteristic

Description

Host Grass Species

bentgrass, bermudagrass, bluegrasses

Month(s) with symptoms

November to March

Stand Symptoms

spots, circles, patches (4 to 12 inches)

Foliar Symptoms - Location/Shape

blighting of entire leaves

Foliar Symptoms - Color

pink, white, tan

Root/Crown Symptoms

none

Fungal Signs

mycelium, jelly-like spore-masses

Note: Still not sure if this is the right disease? The Turfgrass Disease Identification program may be helpful. Or consult the experts at the Turf Diagnostics Lab. Check the TurfFiles glossary for definitions of unfamiliar terms.

FACTORS AFFECTING DISEASE DEVELOPMENT

Disease activity is most severe when snow falls on unfrozen ground; however, activity can occur without snow cover during cool (less than 60°F) wet weather. Excessive foliar growth and thatch buildup are the most important factors encouraging development of pink snow mold and Microdochium patch. Restricted air movement, poor soil drainage, inadequate levels of potassium, and heavy traffic can also enhance the disease. The disease may also develop under tree leaves that remain on the turf for long periods during cold, wet weather.

CULTURAL CONTROL

Do not apply nitrogen when cold weather is expected or before the first expected prolonged snow cover. Continue mowing in the fall until foliar growth stops completely. These steps will prevent a buildup of lush foliage that is highly prone to pink snow mold or Microdochium patch.

Apply a high-potassium fertilizer in late fall to increase the cold hardiness of the turf. Improve surface drainage, control traffic patterns, reduce thatch accumulations, and aerify regularly in areas that have been severely affected by the disease in the past. Prune trees and remove unwanted vegetation that impedes air movement. Frequently remove leaves and other debris during autumn and winter from turf that is not covered with snow.

In regions where heavy snow is anticipated, take steps to minimize the duration of snow cover. Erect snow fences or plant landscape plants in strategic locations to prevent excess snow accumulation. Prevent traffic on snow-covered turf, as compacted snow will melt more slowly and increase damage from pink snow mold.

CHEMICAL CONTROL

Fungicides are effective for control of pink snow mold and Microdochium patch. In the case of pink snow mold, apply fungicides before snow cover to prevent disease development. Mapping and spot-treatment of areas where pink snow mold is most severe can significantly reduce fungicide expenditures. In regions where prolonged snow cover does not occur, apply fungicides when symptoms of Microdochium patch are first observed.

Fungicide	Efficacy ⁽¹⁾	Resistance Risk ⁽²⁾	Class ⁽³⁾	Products ⁽⁴⁾
quintozene	++++	2	aromatic hydrocarbon	PCNB, Terraclor, Turfcide
fludioxonil	++++	2	phenylpyrolle	Medallion
thiophanate-methyl	+++	6	benzimidazole	3336, Fungo, Systec, T-Storm
iprodione**	+++	4	dicarboxamide	26GT, Iprodione Pro
propiconazole	+++	4	DMI	Banner MAXX, Propiconazole G-Pro, Propiconazole Pro, Quali-Pro Propiconazole, Savvi, Spectator
triticonazole	+++	4	DMI	Trinity
polyoxin D	+++	4	polyoxins	Endorse
trifloxystrobin	+++	6	QoI	Compass
chloroneb	++	2	aromatic hydrocarbon	Teremec, Terraneb
vinclozolin**	++	4	dicarboxamide	Curalan, Touche
fenarimol**	++	4	DMI	Rubigan
myclobutanil	++	4	DMI	Eagle
triadimefon	++	4	DMI	Bayleton
chlorothalonil**	++	2	nitrile	Daconil, Chlorostar, Echo, Manicure
azoxystrobin	++	6	QoI	Heritage
fluoxastrobin	++	6	QoI	Disarm
pyraclostrobin	++	6	QoI	Insignia
mancozeb**	+	2	dithiocarbamate	Fore, Dithane, Protect
maneb**	+	2	dithiocarbamate	Pentathlon
thiram**	+	2	dithiocarbamate	Spotrete

** Not for application to residential lawns.
*Footnotes:*
(1)	*Efficacy Codes:*
	++++	excellent control when conditions are highly favorable for disease development
	+++	good control when disease pressure is high, or excellent control when disease pressure is moderate
	++	good control when disease pressure is moderate, excellent control when disease pressure is low
	+	good control when disease pressure is low
	0	does not provide adequate control under any conditions
	?	cannot be rated due to insufficient data
(2)	*Resistance Risk:*
	1	Rotating and tank-mixing not necessary, but recommended to avoid potential side effects from continuous use of same chemical class.
	2	Rotate to different chemical class after 3-4 applications; tank-mixing not necessary.
	3	Rotate to different chemical class after 2-3 applications; tank-mixing not necessary.
	4	Rotate to different chemical class after 1-2 applications; tank-mixing not necessary.
	6	Rotate to different chemical class after 1-2 applications; tank-mixing with low or moderate risk product recommended.
	9	Rotate to different chemical class after EVERY application; tank-mix with low or moderate risk product for EVERY application.
(3)	Continual use of fungicides with similar control mechanisms (modes of action) can result in fungi that are resistant to some chemicals. Poor or ineffective disease control can be expected when this occurs. Managers can reduce the chances of this happening by m

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MICRODOCHIUM PATCH