Lawn Problem

Lawn problems, especially diseases, are very hard to diagnose from a photo. You might want to take a sample of the turf to your local nursery for positive id. It may not even be a disease. How often does the area get watered? Is the problem just in one spot (I’m a little suspect that this happening right next to the hose connection and in a narrow area–water issue too much or too little) ? Are sprinklers covering the lawn evenly? Are there any signs of insects in the soil on the edge of damaged areas (sometimes you can bring them to the surface by drenching the area with soapy water) ? As you can see, there are many things that could be happening. You may have to renovate the area. add organic matter and replant but first you need to be sure of whats happening.
Keep in mind, lawn fungicides must be used repeated (often every two weeks) to be effective. Also, most lawn diseases are a result of poor cultural practices, but with a lot rain, its tough.
Sorry we aren’t of more help. This may help: http://archive.agric.wa.gov.au/PC_92845.html?s=1001