My rot, and coincidentally borer damage, shows up in the part of the front yard that was a former cul-de-sac, left in place except for trenching for utilities. The broken asphalt and rocks were mixed with clay to make the "top soil." Drainage is not great as the excess water just hits the pavement below and keeps the "soil" wet. In the heat the pavement absorbs and then reflects the solar energy back up to the roots thus requiring watering to moisten.
Arlyn, I don't think the decaying wood is the problem, but the lack of drainage could be a possibility.
