Microdochium patch

Circular tan-to-pink water-soaked patches up to ~20 cm, sometimes with pink mycelium at the margins in humid conditions. Common in temperate oceanic climates.

Symptoms of Microdochium patch include small, circular to irregular patches of thin, discolored turf that may have a pinkish or purplish cast. The patches may appear water-soaked or greasy and may be surrounded by a yellow halo. In advanced stages, the patches may turn brown and the turf may die. Lesions may also appear on leaf blades, which can appear as small, tan to reddish-brown spots with dark brown margins. In severe cases, the disease can lead to significant thinning and bare spots in the affected turf. Mowers can spread the fungus, leading to streaks of disease symptoms on putting greens.

The signs of Microdochium patch include sporodochia, which are salmon colored to orange, on the leaves. These asexual fruiting bodies contain numerous spores (conidia) that may spread with mowers or water. Mycelium at the edge of the patch is also a sign of this disease, although it is not as common as in gray snow mold.

Microdochium patch is caused by the fungus Monographella nivalis. This fungus typically infects the leaf blades of grasses, although it can also infect the crowns and stolons of some species. The fungus produces spores (conidia) that are spread by water splash and mowing, allowing it to infect new areas of turf.

Microdochium patch is most common in cool, wet weather conditions and typically occurs in the fall and early spring. The disease is favored by temperatures between 32 to 45F and prolonged leaf wetness. High humidity and low light intensity also favor the development of the disease. The fungus can survive in the thatch layer and can infect newly emerged leaves in the spring. Microdochium patch is typically more severe in shaded areas and in turf that is mowed frequently.