The fungal pathogen Microdochiumis responsible for causing Fusarium Blight or Patch in turf. The disease appears as small circular patches, water-soaked spots less than 5cm in diameter. The patches change in colour from orange-brown to dark brown and finally to a light gray. The spots may enlarge indefinitely, but are usually less than 20cm in diameter. On low cut turf a halo-like “smoke ring” may appear on the outer margin of the patch.
In very wet conditions a thin to fluffy covering of white mycelium may be seen on matted leaves. The mycelium is white, but on exposure to sunlight induces spore production which is a pink colour. Conditions that favour disease development include more than 10 hours a day of foliar wetness for several consecutive days, cool temperatures, soil high in nitrogen fertility and low phosphorous and potassium and areas with slow growing conditions and heavy thatch.