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Fusarium patch, also called snow mould, is a common cause of brown patches on lawns, particularly in autumn or during mild spells in winter.
Fusarium patch and snow mould
This disease is caused by the fungus Microdochium nivale (formally Fusarium nivale). It is one of the most damaging diseases of turf grasses and can be difficult to control. It is found most frequently during autumn, winter and early spring, but attacks can occur at any time of the year.
The disease is sometimes very noticeable after thaws of snow, when it is given the common name of snow mould.
Fusarium patch is particularly troublesome on annual meadow grass (Poa annua), but can also affect bents (Agrostis species), fescues (Festuca species) and perennial rye-grass (Lolium perenne).
What to look out for;
The only fungicide available to amateur gardeners for control of this disease is trifloxystrobin (Provanto Lawn Disease Control). The fungicide can be used all year round except during drought conditions or when the lawn is frozen. There is a risk of resistance occurring in the fungal population, therefore, the product should not be applied more than twice a year and is best used in conjunction with other control methods.
Some lawn maintenance companies offer treatment for certain diseases with a professional fungicide, but there is strict legislation controlling the application of professional products to domestic gardens. You will therefore need to satisfy yourself that the company is operating within the law.
Inclusion of a fungicide product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener.
The Sports Turf Research Institute recommends using iron sulphate, a mosskiller, to reduce the severity of the disease. This compound toughens the grass and has an acidifying effect on the turf, which in turn discourages snow mould.
Fungicides for gardeners (Adobe Acrobat pdf document outlining fungicides available to gardeners)
Weedkillers for gardeners (Adobe Acrobat pdf document outlining weedkillers and mosskillers available to gardeners)
The fungus can survive temperatures as low as -20°C (-4°F), although the optimum temperature for growth is 12-19°C (54-66°F). Infection can, therefore, occur in summer but is usually masked by rapid grass growth. The disease becomes more apparent as the weather cools and grass growth slows. The fungus requires surface moisture to infect leaves, and grass that is particularly lush due to high nitrogen levels is more prone to attack. Alkaline soil conditions also favour the disease.
Snow mould develops under prolonged snow cover. The combination under snow of a fairly constant temperature of about 0°C (32°F) and increased levels of carbon dioxide are particularly favourable for Microdochium nivale. Another fungal disease called grey snow mould, caused by Typhula incarnata, can also develop under these conditions. The patch symptoms are similar but any fungal growth seen is greyish-white rather than pink. Typhula also produces tiny, brown, hard resting bodies, often looking like small seeds, scattered over the affected grass.
Fusarium patch is spread across the lawn by the transfer of spores of the fungus or infected grass debris on equipment or shoes.
Chafer grubs in lawns
Lawns in shade
Lawns: autumn care
Lawns: care during drought
Lawns: dead patches
Lawns: dry patch
Lawns: spring and summer care
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