Once identified, fungal pathogens in turf can usually be remedied by cultural control
Hosts
All types of turf, but fine-leaved grasses, such as fescues and bents, are generally more susceptible than ryegrass.
Common symptoms
Brown patches followed by fluffy white fungal growth (snow mould) (left) or small spiky pink structures (red thread) (right). Yellowing or browning of individual leaves (leaf spots). Fairy rings are more easily identified.
Biology
Snow mould and red thread are the most important diseases. Snow mould (Monographella nivalis) occurs at cool times of the year. Red thread, caused by Laetisaria fuciforme, is often encouraged by nitrogen deficiency in the soil. Various other fungi cause leaf spots, root disease, powdery mildew and rusts. The fungus causing take-all patch, Gaeumanomyces graminis, attacks and kills the roots. Pythium species are occasionally a problem in wet conditions. Dollar spot (Sclerotinia homoeocarpa) is often mentioned in books but very rarely seen by the RHS Advisory Service.
All these fungi are spread by spores, whether airborne (mildews, rusts, some leaf spots), by rain splash (snow mould, pythiums) or carried on footwear and mowers.
Control
Moss killers containing iron sulphate have an incidental controlling effect on snow mould. Home gardeners should rely on cultural methods to reduce fungal problems, as no chemical controls are available to them. Snow mould, red thread and other leaf diseases cause damage, but seldom kill grass.
Spiking to improve drainage and feeding lawns in spring encourages new growth, helping grass grow through the problem. Avoid nitrogen-rich fertilisers in autumn, as this encourages disease-prone soft growth. ‘Swishing’ turf in the morning with a dew switch (long, pliable rod used to disperse dew) hastens drying. While mowing may spread spores, it also reduces humidity, removes infected material and promotes new growth, so is beneficial overall.