Sometimes a lawn service will want to get rid of a fungus in a lawn or in the soil. In my opinion probably the only thing most can do is spray a fungicide which
is a particularly nasty chemical. Feeding the lawn is elegantly simple
and far more effective. Occasionally the organic fertilizer application that some use will help the lawn as well as a little change in weather. (weather is a big influence)
But it's a process similar to someone getting over an illness.
Diseases are a calcium, phosphorus and copper deficiency. Plants absorb
10x faster thru the leaves than thru the roots. I recommend a nice calcium-phosphorus-copper in liquid form that is highly effective. The process usually starts after just one feeding but if the nutrient deficiency is deep then it might need to be fed more often until I get good results.
I also recommend a microbe tea application (which Chris can do) and this will put many probiotics in the soil that can digest minerals and make it available to the lawn. Plants don't have a stomach so the digestion has to happen in the soil and these probiotics do a great job of making food available.
I hope this helps! I have a lot of experience controlling diseases with nutrition.
Powdery mildew affects the top (blades) of the grass and does not kill the roots so you will not lose your lawn. The roots will push out new grass and grow out of this problem.
Usually a disease can be fixed with nutrition but at last resort after getting the soil and lawn healthy again you can turn to a fungicide.
It's similar to you or I getting sick and addressing the issues first and getting healthy... then turning to medicine if needed.