The grass maybe suffering from Red Thread disease which normally occurs between June and September and is most evident on the finer leaved fescue grasses. Currently we do not have a fungicide for this problem.
Several cultural practices will also help the recovery of the lawn. Red Thread tends to attack lawns that are starved and have compacted soils.
Deep spiking (10 to 20cm) of the lawn to aerate and improve the drainage will also relieve any compaction. Take care to sterilise the fork or aerator when moving from infected to clear areas, to prevent spreading the infection.
Feeding the lawn throughout the year with either the Scotts Lawn Builder or EverGreen range of lawn care fertilisers, will keep the lawn strong and healthy, which will enable it to cope with this disease and compensate for any damage.
Application of an Autumn feed later in the season that contains high levels of potash and a lower level of nitrogen, toughens growth against this disease and prepares it for Winter.