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.

HI Stephen, Lots of insects will take up residency in rotted area of wood. they are genrally opportunistic and are not injurious to the tree. We dont recommend any treatment or sealant as it would just create an even wetter area. the tree does what it needs to do to wall off the affected area. you may also want to contact your local extension office for local information. this website should help you find an office near you. http://www.gardening.cornell.edu/