Snow mould and how to avoid it

Garden Life
Snow mould is a lawn disease indicating that the grass is suffering from a fungal infection. Snow mould usually occurs in cool and humid weather. At temperatures of around 3° C, it is one of the most frequent disease-causing pathogens on lawns. Mild, rainy weather also promotes the propagation of snow mould. The term “snow mould” is in fact misleading, as the disease also frequently occurs when there is no snow.
The disease, which is often called “snow mould”, is not just limited to the winter months. This fungus can occur at any time of year in cool weather conditions and after temperature fluctuations. The mould grows particularly well at temperatures of between 0 and 8° C. The snow mould does not spread after temperatures exceed 20° C. The disease frequently occurs in combination with other winter diseases.

Causes

As with many disease-causing pathogens, the snow mould pathogens are always present. However, the disease only breaks out if the conditions are favourable for it. This includes the resistance of the lawn being weakened and the temperatures being humid and cool. 

•  Humidity and temperature fluctuations
•  Particularly mild and rainy weather
•  Grass cuttings and autumn leaves on the grass
•  Sustained humidity through dew and mist
•  A lack of air circulation (due to walls or hedges)
•  A closed covering of snow over a prolonged time period
•  Walking on the lawn when it is covered in frost
•  Potassium deficiency

Disease pattern

If attacked by snow mould, the lawn will first suffer small, round patches which slowly grow larger and spread. They are brown in colour with a grey-white edge. The patches in the lawn regenerate from the centre outwards.

Control

As the temperatures rise, the fungi stops growing and the patches on the lawn will automatically recover. To accelerate recovery, you can process these areas regularly using a lawn aerator. In order to get rid of the ugly patches, re-sow with grass seed.

Prevention

A healthy, well cared-for lawn is more resistant to snow mould. For this reason, correct lawn care is the optimum prevention against snow mould. After ending the games season or active use of the lawn, a final cleaning cut in autumn will lead to improved aeration of the turf and will allow it to dry out more quickly. In autumn and winter, the leaves should also be regularly removed from the lawn. In spring, moss and dead material can be removed from the lawn area using a rake. In this way, infected plant material is removed and the circulation of air and light is promoted.
Distribute fertiliser containing lots of potassium in autumn. A high potassium content promotes the strength of the cell walls and increases the salt content in the plant cells. In this way, potassium lowers the freezing point of the cell saps and reduces frost damage. Avoid autumn fertiliser with a lot of nitrogen or lime.
Over the course of the year, lawn aeration, light aeration and sanding are recommended in order to provide lawns with optimum protection against snow mould.