Red Thread

This is a disease of wide spread distribution on amenity turf. It was believed that the symptoms of Red Thread were caused by one fungus. However, following examination of the fungi present, two organisms are currently regarded as having a role to play in the development of this disease. One of these organisms is the fungus limonomyces roseipellis (pink patch). The principal fungus responsible for Red Thread is laetisaria fuciformis.


Red Thread is usually seen during the summer and autumn months, although the disease may be present into the winter months if the conditions remain mild. The disease appears as patches of damaged grass which often have a pink or red appearance. This is due partly to the presence of red “needles” which protrude from the diseased leaves. These needles are the survival phase of the fungus. The needles may be straight or branched, brittle, and up to 25mm in length. The size of the infected patches vary in diameter, unless the grass growth is poor and the attack serious. Damage to the leaf is fairly superficial in appearance which die back from the tips.

Conditions which favour the disease

The fungus causing this disease is favoured by mild temperatures and a damp turf surface, it can occur in almost any area in amenity turf and root zone. Generally the disease appears during spring and worsens during the summer/autumn. It is possible for the disease to occur all year round if the environmental conditions remain favourable. Autumn attacks may be quite severe as the fungus takes advantage of your grass entering dormancy. The disease can be associated with grass with low nitrogen levels, however, it has been noted over recent years that lawns regularly receiving adequate nitrogen fertiliser have developed severe outbreaks of this disease. It appears that localised change within the pathogen population have allowed the development of a more aggressive strain of this fungus.

Disease Control

Since the disease can be associated with conditions of low fertility, especially nitrogen, it may be sufficient to apply a suitable fertiliser to allow the turf to grow away from the disease. However, if the development of a more aggressive strain of the fungus occurs during summer/autumn, it may be advisable to rely on a fungicide application to control this disease.