Other common names:
Fusarium, Winter Fusarium, Fusarium Patch, Gerlachia Patch.
Winter Fusarium is caused by the fungus Microdochium nivale (previously called Fusarium nivale). It was identified for many years as a Fusarium species, hence the usage of the name Fusarium. It is primarily a cool-season and winter disease, and a pathogen of cool-season turf. However, it has been recorded on warm-season turfgrasses species. It is often characterised by an orange/brown colour in the patch and patch borders of the affected area(s) of the turfgrass.
Lifecycle: Symptoms are evident from May to September under favourable conditions. Fusarium survives through the spring and summer as spores and mycelium in the thatch or soil when temperatures are above 16°C or when it is dry. Under cool, wet weather, spores may germinate or mycelium may grow from thatch or soil and infect leaves within the turf canopy (Hsiang, 2007).
Fusarium can attack all cool-season grass species; however browntop and creeping bentgrass (Agrostis spp.), Kentucky bluegrass (Poa pratensis) and perennial ryegrass (Lolium perenne) are more susceptible. Poa/wintergrass (Poa annual) and tall and fine fescue (Fescue spp). are also commonly infected in New South Wales, South Australia, Tasmania and Victoria. Hybrid green couch (Tif varieties) have also seen fusarium damage on the foliage.
Symptoms develop slowly and from the time an initial infection occurs until symptoms are clearly visible can take several weeks. The circular patches less than 5 cm in diameter first appear as water-soaked spots, then rapidly change colour to tan, brown, dark brown and finally light grey. Patches can enlarge up to 20 cm in diameter overtime. At times fungal mycelium may be seen within the turf canopy of the affected area. The mycelium is white in colour, but in direct sunlight induces spore production which is a pink colour. In the USA Fusarium patch is often called pink snow mould because of the pink colour. Fusarium patch and pink snow mould are caused by the same fungus, however they can be considered two different diseases because of their environmental conditions needed i.e. Microdochium nivale is often termed Fusarium patch when it occurs in the absence of snow cover. Fusarium favours cool temperate areas, which have prolonged periods of cool, wet weather. Shaded areas of turf are more susceptible than turf grown in full sun. Fusarium also favours high thatch levels. Spores can be transferred by water movement, machinery and foot traffic, so problematic areas can quickly spread.
Hsiang, T. 2007. All you ever wanted to know about Fusarium Patch. AGSA Turf News, June 2007, pp. 13-16.
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