Lawn diseases

There are many turf diseases, most of which are unlikely to appear on the average lawn. We will therefore consider the most common ones. Most diseases can be avoided by ensuring that aeration is carried out regularly either by scarifying, true aeration or both.

Red thread

This is a fungal condition that we are seeing more of in recent years. It is usually triggered by humidity when the soil surface is warm and moist. It presents itself initially as small patches of discoloured grass, and in its early stages either tiny red needles or pink candy floss like structures can be seen. It can be treated by use of a preventative fungicide but needs to be identified early. If it is allowed to spread then it can disfigure the lawn for all summer. It will eventually grow out once conditions change, and keeping the nitrogen levels up will help.

Fairy rings

This condition is again becoming more widespread. Fairy rings are caused by a fungal element in the soil which creates mycelium, a white mildew like substance that smells mouldy. It is often in the form of a ring, but can equally be in a line. There are different types, and can appear as either areas of dead grass often accompanied by toadstools, just a ring of toadstools or just a ring of grass with more excessive growth. They will move through the soil profile contaminating fresh soil. The dead grass in the centre usually has areas of exaggerated growth either side. This occurs because the process releases excessive nitrogen. Mycelium also causes the soil to become hydrophobic and therefore will repel any moisture.

No one really knows what causes fairy rings, but at present there is no chemical treatment available. Masking them with different products can work but digging out the contaminated soil is probably the most likely solution.

Fusarium (snow mould)

This is a cooler weather condition where the signs are similar to that of red thread, but the fungal growth on the leaf is white. It is often found after snow has melted, and can be treated with either fungicides, or often just by feeding.

Hydrophobic Dry Patch

This is a condition where the soil is infected with a fungi which coats the soil particles with a wax like substance. This then makes the soil repel moisture and the grass plant dies of drought stress. This condition is normally controlled by natural rainfall, where the fungi are not allowed to build up. In dry conditions, or where excessive thatch is present it can mean that not enough moisture is passing through the soil profile to cleanse it, and dry patch occurs. It can be remedied by aeration and application of a wetting agent which cleanses the soil and allows moisture to penetrate again.