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A guide to the most common lawn diseases by Tillers Turf

A well-maintained lawn, growing in a well-structured, healthy soil will not normally be troubled unduly by grass diseases. Although the spores of most common diseases are found in all swards, the effects only usually become pathogenic, or damaging, when the grass is under stress.

Grass can be stressed by a number of factors, including: mowing too short, waterlogging, over feeding, under feeding, soil compaction. Transplantation during turfing can also stress the grass to a point where it becomes susceptible to disease.

Occasionally even healthy turf can be seriously affected by disease. This normally happens when weather conditions favour the growth of the pathogen at a time when grass growth is slow.

The most common lawn grass diseases are Fusarium, Red Thread, and Fairy Ring.

Below is a short guide to these diseases to help you identify and treat them should they occur.

Fusarium

Fusarium patch disease is the most common disease of turf in the UK. The Latin name of the fungus that causes the disease symptoms is Microdochium nivale but in the past its Latin name was Fusarium nivale, hence its common name.

Fusarium appears as irregularly shaped range-brown areas of turf a few centimetres in diameter develop, sometimes with a white or pink fluffy fungal growth around the edge of the patch. Over a period of weeks these dieback and can create areas of bare ground. These gradually recover naturally if weather and soil conditions are warm enough. However, if the disease occurs in the autumn, the conditions may not be suitable for recovery until the following spring. In most cases, the diseased area will completely recover once the grass is actively growing again.

Fusarium is likely to appear whenever the weather is very still and humid and the grass stays wet for most of the day. Fusarium is rarely a problem in the summer but is very common at other times of year under these weather conditions. The fungus grows in the water film on the grass leaf andthat is why heavy dews and still air favour its spread.

To help prevent Fusarium avoid over-feeding. Avoid damp, shady locations with still stagnant air for laying turf. In order to keep the lawn surface dry, mow regularly to prevent the leaves of the grass becoming too long. Air movement dries the lawn surface, making conditions less suitable for growth of fungal diseases. The condition of the soil under the turf is very important in defending against disease attack. A well structured, free-draining soil will help produce healthy turf.

There are currently no fungicides recommended for use by amateur gardeners in the UK to control this disease.

Red Thread

Red thread disease is one of the most common diseases of turf in the UK. The Latin name of the fungus that causes the disease symptoms is Laetisaria fuciformis. The disease is usually not very harmful and usually causes no permanent damage, but it can be unsightly.

Red Thread is irregularly shaped, pale pink areas of turf with the leaves of the grass often dying and matted together by fungal growth occurring in the growing season. Often there are pink fluffy fungal growths or coral red needle-like out-growths, which give the disease its name of red thread.

Red Thread can affect lawns with low nitrogen fertility. Low fertility often leads to more dead leaf in the turf, which is one of the symptoms of the disease. Some grasses are more susceptible to red thread than others. Perennial ryegrass and red fescue, which are commonly used to produce turf for sale, are frequently infected. The spores of disease fungi are present everywhere and red thread disease may attack a lawn if the climatic conditions are right, even if all the necessary precautions have been taken, and then not reappear for sometime.

A well-structured, free-draining soil will help to produce healthy turf. Using a pre-turfing fertiliser will help prevent its development on less fertile sites. Once the turf has rooted down and established, the lawn should be fed occasionally in the normal way using a fertiliser with a high nitrogen content.

There are currently no fungicides recommended for use by amateur gardeners in the UK to control red thread. It is usually not necessary to use fungicides for the control of this disease, as it rarely kills the grass outright.

Fairy Rings

Fairy Rings appear as a ring of lush green grass containing mushrooms or fungi. These are a turf disease caused by many different types of fungi. The rings are started by active fungus in the turf and they keep growing indefinitely. The fungi breaks down organic matter and releases it as nitrogen, this is what causes the dark green ring on the surface of the lawn. If you dig out section of the fairy ring you can sometimes find white threads. This white fungus is called 'mycelium' and it has a strong musty smell. There are three different types of fairy rings, some can be more damaging than others.

The first type of fairy ring is the most damaging on the garden lawn. These rings actually kill the grass where as other types 2 and 3 do not kill the plant. A Grade 1 fairy ring can be identified by a ring of dead grass about 10 -30cm across in which mushrooms and fungi can be found in early spring and autumn. If you dig below the dead zone you will find the mycelium will be more dense than other areas of the fairy ring. Mycelium is hydrophobic (water repellent) therefore any rainfall or irrigation applied is repelled from this area. This causes the dead area in a grade 1 fairy ring in which weeds and moss can invade and become a problem.

The second type of fairy ring can be identified by lush green rings or arcs. Sometimes mushrooms or puffballs may be present. It is not as damaging as a type 1 fairy ring as it does not kill the grass - the only problems being the fruiting bodies or the visual effect of the green ring or arc.

The third type of fairy ring can be identified by its fruiting bodies of mushrooms and puffball. It does not produce a ring of dark green grass. The only problem therefore is the nuisance value of the fruiting bodies especially if they are extensive. The fruiting bodies can form rings, arcs or they can be solitary.

The control of fairy rings on garden lawns can be quite difficult. This is because there are no real cures apart from completely digging it out of the lawn. If your lawn has grade 2 and 3 fairy rings the problem can be masked by applications of nitrogen or sulphate of iron. These products promote a deep green colour which will help the fairy ring blend in with the lawn.

If you have a grade 1 fairy ring again applying products to mask the colour of the green ring can help. The real problem will be the hydrophobic layer below the surface which causes the dead area. This area can be spiked and a wetting agent can be applied before the area becomes dry. This operation can be repeated as necessary. Once the area has become too dry it will be very difficult to re wet.

The other way is to completely dig out the fairy ring. This means removing the soil to a depth of at least 30cm (12in). Then remove 50cm (20in) in front of the inside of the ring and 50cm (20in) beyond the outside of the ring. Be careful not to spill any of the infected soil onto the lawn during the removal process. Replace infected soil with fresh soil and reseed the area.

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