Fusarium patch

This disease is caused by the fungus Microdochium nivale (formally Fusarium nivale). It is one of the most damaging diseases of turf grasses and can be difficult to control. It is found most frequently during autumn, winter and early spring, but attacks can occur at any time of the year.

The disease is sometimes very noticeable after thaws of snow, when it is given the common name of snow mould.
Fusarium patch is particularly troublesome on annual meadow grass (Poa annua), but can also affect bents (Agrostisspecies), fescues (Festuca species) and perennial rye-grass (Lolium perenne).

Symptoms
The disease is first noticed as small patches of yellowish, dying grass that later turn brown
Patches increase in size and may reach 30cm (12in) or more in diameter, often merging together so that large areas can be affected
During wet conditions a white or pinkish, cottony fungal growth may be noticed, particularly at the margins of the patch. This is not to be confused with another fungal disease called red thread, or with slime moulds in turf