IPM Identification and Mangement Of Turfgrass Diseases

Author(s)

Microdochium Patch
(pink snow mold)

Pathogen: Microdochium nivale
Hosts: Bentgrass, annual bluegrass, occasionally perennial ryegrass and Kentucky bluegrass

Symptoms and signs

Symptoms of Microdochium patch are variable. On creeping bentgrass, the more familiar symptom is a distinct circular to irregular patch ranging in size from 1 to 8 inches in diameter (Figure 1). The patch appears red-brown and water-soaked at first, but rapidly fades to a pinkish white with a red-brown border. Microdochium patch on creeping bentgrass can also occur as a water-soaked, reddish foliar blight instead of a distinct patch. The foliar blight phase is especially common in mid to late spring. In this foliar blight phase, Microdochium nivale is readily spread by mowing. Because the symptom pattern coincides with the mowing pattern, the disease has been misdiagnosed as Pythium foliar blight because the latter is also readily spread by mowing. Pythium foliar blight, however, is a high-temperature disease. On higher cut turf such as Kentucky bluegrass, abundant mycelium (aggregate mass of vegetative growth) can often be seen in association with blighted turfgrass (Figure 2).

The pink color is due in part to the development of fruiting bodies known as sporodochia. The white to pink sporodochia are abundant on the leaf surface under cool wet conditions (Figure 3). Conidia produced on the sporodochia are crescent shaped with one or two septa (cross-walls) (Figure 4).
Spring outbreaks of Microdochium patch on putting surfaces are often mild with a few sporadic patches per green. The disease is often observed in association with yellow patch. The symptoms generally disappear with warmer temperatures.

Conditions

The growth of M. nivale is favored by cool temperatures (32 to 46°F) and high relative humidity or frequent precipitation. Even with warmer daytime temperatures in the spring, Microdochium patch can develop in response to nighttime temperatures in the high 40s to low 50s and frequent rainfall.

Dense, lush growth resulting from heavy nitrogen application is especially susceptible to M. nivale. The disease is more severe on new greens, greens under cover or greens that have been repaired with overseeding and heavy fertilization to promote recovery.

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.