Fusarium is a condition caused by a particular type of fungi, called Microdochium nivale which is only able to grow at temperatures between 1o and 10oC. Therefore, Fusarium (which is sometimes also referred to as Fusarium Patch) is regarded as being potentially a year-round problem, usually linked with cool, humid conditions. It is also associated with high nitrogen fertility and thatchy, poorly drained soil, or under shade. It is also is more likely on alkaline soils. The fungi need the presence of water in which to grow, and infection of the grass plant only takes place after a period of leaf wetness. The ideal weather for Fusarium to flourish is periods of frost, interspersed with cold wet conditions, although, as stated earlier, Fusarium can occur at any time of the year, if wet or humid conditions occur. The main symptom is rapidly developing circular patches of 25-50mm in diameter. In serious cases, the patches can converge, and may not, therefore, be recognised as being circular. The grass leaves can become brown and mushy. Sometimes pink or white cobweb-like fungal threads can be seen in early morning.
In order to control Fusarium, good turf management is necessary to promote healthy, vigorous growth. Regular spiking and careful application of fertilisers, combined with a sandy compost, will make the surface less moisture retentive. Removing dew from the lawn by brushing is also beneficial to reducing the onset of infection. Increasing the movement of air across the sward will be particularly helpful as will reducing water holding thatch. When mowing, always ensure clippings are collected to prevent development of a substrate which will promote disease. There are a range of fungicides which are effective against this disease, but they need to be combined with sound turf management practices to reduce the environmental conditions which are favourable to Fusarium development.