Fusarium, or Fusarium Patch, is a Mycelium Fungus which is often described as the bane of Greenkeepers.
It is common throughout the northern hemisphere and thrives in damp, mild conditions which makes autumn its prime time for getting started. Fusarium needs temperatures below 20 degrees Celsius in order to flourish, so British summers will seldom see any growth of the disease.
Fusarium starts as small orangey-red-brown, round spots and will keep growing if unchecked. These patches of discolouration will eventually become pale circles, with a white, slimy coating
How does it come about?
If the cool & wet conditions of winter continue through springtime, Fusarium may truly thrive. Frost will kill it, but your lawn may be scarred temporarily and Poa Annua grass may settle in the bare patches left behind by the Fusarium. The Poa Annua (or Perennial Meadow Grass) is notorious for harbouring the Mycelium spores which then go on to create a vicious circle of new Fusarium growth. Over-seeding in spring or autumn with grass species which overwhelm the Poa Annua will help to counter this invasion, as will the use of fertilisers and aeration programmes which encourage other grass species such as Fescues and Bents.
Young grass plants are more susceptible to fusarium, so as autumn approaches it is better to use slow-release fertilisers so as to minimise spurts of new growth and spread out that development to ward off the attention of the Fusarium.
Preventing the spread
Fusarium is happy to lurk within the thatch layers of your lawn, so stay vigilant and aerate to help oxygenate the sward. Clear airflow over the grass also helps keep the mycelium spores on the move, preventing them from getting established.
Many advocate the use of fungicides when tackling Fusarium, and these will take one of two forms; Curative and Preventative:
Curative Fungicides slow down and eventually stop the fungus from damaging an already-infected grass plant, while Preventative Fungicides work by stopping Fusarium from getting established in the first place, inhibiting the disease before it can become ensconced.
Whichever of these apply in your case, we would recommend that you seek professional advice before setting out to use any form of fungicide.