The first step to getting rid of any lawn disease is to identify and understand what is happening to your lawn. Brown patch fungus can be very damaging to your lawn. It begins with small patches of lawn turning straw colored, brown or reddish brown. These patches start out about 1 foot in diameter. These patches can continue to spread and kill the grass leaves. This lawn disease does not affect the root of grass, making it possible to return the grass to its original green color. This disease is basically rotting the grass starting at its base.