Ophiobolus is a fatal disease, so obviously - as with all things fatal - prevention works far better than cure! The good news is, that is is probably one of the least common of lawn diseases for it normally affects grasses in the Bent group, and is usually associated with poor drainage, inadequate feeding and also a high calcium level in the soil.
It is a fungus disease which usually takes place in cool periods, but does not become evident until warmer weather periods. By this time, the damage has been done. Affected grasses will not re-grow.
Opiobolus Disease Patch
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Ophiobolus starts as a small slightly sunken patch in the lawn which is accompanied by tell-tale browning, followed by yellowing of the grasses. The patch can be as much as 2metres across in the first year of infection.
Finer grasses die out in the centre of the patch, but coarser grasses will probably persist - together with some weeds. The edges of the normally circular patch are often orange in colour.
Gaeumannomyces graminis var. avenae is the botanical or scientific name of All Patch Disease - Ophiobolus. It is not a common disease in the UK, but sometimes occurs with catastrophic results on golf green. Such areas necessarily include the 'Browntop' bents (Agrostis spp) in their grass mix.
It is rarely of ever, found in turf areas of a low soil ph level. Geographically, this means that areas of high ph soil levels will be more likely to be troubled with the disease.
A natural parasitic fungi - Phialophora radicicola - is widespread in the UK, and where it is present, there is rarely any problem with Ophiobolus - Take All Patch. It is effective enough for it to be widely used by way of soil injection in other parts of the world where the Ophiobolus Patch is troublesome. In terms of preventative methods, the use of wide spectrum fungicides should be restricted so as to keep the population of Phialophora radiciola in the turf area. Where the parasitic fungi is present, there will be no Take All Patch disease.
Preventative treatment is basically normal lawn maintenance, with a good feeding regime and aeration. Where there is possibility of of the disease - high Agrostis spp turf, then consider the use of Sulphate of Ammonia as main Nitrogenous feed. This will have an acidifying affect upon the soil. If there are small patches in the early stage of infection, then the areas can be spiked, fed and new turf installed. The dead grasses within the circular brown patch will not recover.
If you feel that you may have over-limed your soil, then do a soil test, and then rectify the alkaline content (PH level, with the use of a soil acidifier). Rhododendron feed/treatment may do the trick. Likewise, alter your feeding regime to include Ammonium Sulphate as the main source of Nitrogen fertiliser.
There is no point trying to 'cure' it after appearance. Simply dig up the dead area and re-seed or re-turf.
Above all, it should be stressed that this is a disease only of Agrostis - Bents - Browntop grasses so is not likely to be the first suspected cause if you have brown patches on your lawn.