I discovered a section of the main trunk, about 1 foot up from the ground, which had turned mossy and black and was quite spongy. I began to dig it out and a number of ants and what appeared to be pupa buried just beneath the bark began to fall out. The wood was soft, so I scraped out the infected wood until I reached healthy wood underneath. Is there something I can treat this area with or perhaps apply a dressing to seal it, prevent further infestation and allow this area to heal? This is a healthy, 150 year-old tree, about 70 feet tall and I don't want to lose it.