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, but can also affect bents, fescues and perennial rye-grass.
What to look out for;
A fungicide can be used all year round except during drought conditions or when the lawn is frozen. There is a risk of resistance occurring in the fungal population, therefore, the product should not be applied more than twice a year and is best used in conjunction with other control methods.