Thank you so, Keith ..
I did not know of this Thousand Canker dis-ease, but truly appreciate information instead of snotty comments, and will garner what I can from that, for continued prevention and safekeeping of my beloved trees.
I'm in central Ohio, and this past Winter was truly brutal; the weight of the ice did indeed break some branches.
In the meanwhile, I did treat all the bases in that stand, a heavy ring at the soil, then up the trunks with a brush, and all along the base of my wood fenceline with the Diotomaceous Earth, and you should have seen the result! It totally gacked them out, they swarmed, en masse, and I ... well .. killed them. And yes, I have been watching, applying a bit more to see if that too produces any activity, and as yet - none.
The main colony seemed to indeed be in that poor, reddened stump, and it is of note that it has collapsed quite a bit, hopefully as a result of the mass of the creatures themselves dying back.
DE is such an amazing thing, so benign and yet insidious. Today, just to be safer, I am going to 'paint' it onto the steps down to my cellar (I live in an old farmhouse), because they just - will not - cross that, as they seem to know it's gonna shred them. It is also a powerful source of nutrients for soil, full of calcium, nitrogen, potassium, trace minerals, etc. as it is basically ground seashell, and it's a wonderful thing to add in to your Spring mix of peat, manure, compost, or what ever you till your garden soil with.
Again, much appreciated,
Peggy