It is definitely not brown patch and doesn't look like grubs or chinch bugs either. My best visual assessment is that it is take-all patch.
The answer to your question is rather complicated but here are the basic facts. Most fungicides do not work well, and the effect is temporary. The standard recommendation has been to use myclobutanil (example products include Spectricide Immunox or GreenLight Fung-Away Systemic Granules or Ferti-lome f-Stop) or propiconazole (e.g. Fertilome Liquid Systemic Fungicide or Banner MAXX). These products work well but have a drawback. They are sterol inhibitors which means they move into the plant tissue and then have some upward movement in the plant. It also means that they have an inhibiting effect on regrowth. So used to prevent a Take All Patch problem from growing they would work fine. If the yard is in an advanced stage of decline they would kill the fungus causing the problem but the grass would not recover as quickly as you might like.
So that considered I think two better choices to consider would be thiophanate-methyl (e.g. Clearys 3336, Scott?s Lawn Fungus Control Granules or Green Light Systemic Fungicide Disease Control) or azoxystrobin (e.g. Heritage). Thiophanate-methyl has shown some effectiveness in controlling Take All Patch. Azoxystrobin is probably the most effective but is not available without a pesticide applicator?s license, and is quite expensive. Neither of these two products has the growth inhibiting effect of the previous two and therefore both would allow for faster recovery.
Another approach that has proven effective in Texas research is the use of sphagnum peat moss. Take the compressed product and break it up into a light fluffy material. Then spread it at a rate of one 3.8 cu ft bale per 1,000 square feet of lawn area. A little thicker if fine, but the 2" rate you were advised to use is way too deep. Dump small piles of the loosened product around the lawn. A standard garden soil rake (not a leaf rake) can be turned upside down and used in a motion similar to playing shuffleboard to spread the piles around evenly. One bale will cover 1,000 square feet about 1/3 inch thick which is just about right. After spreading the moss water it in well.
For more info on using peat moss to manage Take All Patch in lawns see the following web site:
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