The below aims to tackle one of the more common lawn ailments, Fusarium.

What is it?

The most common disease of turf in the UK, according to Harrowden Turf.

The Latin name for this fungus is actually Microdochium nivale. A former Latin name was Fusarium nivale – hence the name: Fusarium patch. The fungus is also referred to as ‘Snow mould’ due to the fact it is often seen after snow has thawed from a garden.

Three turf grass species commonly grown in the UK are susceptible to Fusarium:

• Annual meadow grass (Poa annua)
• Perennial ryegrass (Lolium perenne)
• Creeping bent (Agrostis stolonifera)

These grasses are commonly found in domestic rolled turf, golf courses and bowling greens.

What are the symptoms?

Fusarium is first identifiable by small (1-2 centimetres) orange/brown patches of turf. Over a period of a few weeks, the size of these patches may grow, join together and form much larger areas of bare ground.  Sometimes, often during wet weather, white/pink coloured mycelial growth will develop around the edge of the bare patch.

Why does it appear?

Fusarium spores and mycelium are abundant throughout the landscape, year-round. They are more likely to produce symptoms in certain conditions. The disease requires moisture on the surface of the grass in which to grow. Due to this, when the grass stays wet for longer periods, with a temperature between 12 and 19˚C, symptoms are most likely to manifest. For this reason, the disease is likely to be most active in autumn.

Fusarium is not active in temperatures above 20oC or when the surface of the grass sward has insufficient water. As a result, Fusarium is not normally active during the summer, and faster grass growth during this period makes symptoms less obvious.

Beneath a layer of snow, the fungus will thrive in high carbon dioxide with constant temperature. When the snow thaws, large areas of damaged lawn are likely to be visible.

Fusarium initially attacks the outer cell walls of the grass plant. Lignin, a component of cell walls in all plants, acts as a barrier to plant pathogens. It is present in higher quantities in mature plants and less so in younger plants. As a result, young grass found in new turf is more susceptible to Fusarium. Fresh growth encouraged by application of fertilisers is also more vulnerable to Fusarium attack. This means applications should be timed so to avoid a higher risk of attack.

How to control it?

In most cases, diseased turf will recover once the grass is growing between spring and autumn. Fusarium growth can be discouraged by ensuring the grass sward is kept short. This will encourage greater air movement between leaves and a dry surface. Similarly, heavy thatch layers should be removed to aid drainage and encourage air circulation.

Well-structured and free-draining soil beneath the turf will also avoid the damp, humid conditions. Compacted or soils with poor drainage should be a priority to discourage attack.

Avoid trees and shrubs which over-hang turf and encourage damp, shaded conditions.

Chemical control may be in consideration as a form of preventative, curative and fungicide solutions.