Sorry to read that you have that nasty problem. I assume you are in one of the more southerly states? My suspicion is that the soil temperature would not be raised for long enough to kill the sclerotia especially those below the soil surface. Do you have an acidic soil? There are several science based suggestions from the American Phytopathological Society at this link, including using lime to raise the soil pH if it is currently in the acidic range preferred by the fungus. For bulk soil treatment by heat they say steaming to 160-180 degrees F for 30 minutes is necessary and some sclerotia may even survive that which is why I'm doubtful about just pouring boiling water on the soil surface.
http://www.apsnet.org/edcenter...