Sean Freeman

I agree entirely with Eric's comments, loathed to commit without even pics of the tree, every tree grows roots differently every significant root relates to the above ground structure, and the impact of its loss has to be weighed in relation to the shape size wieght distribution of the branch architecture above it. Therefore impossible to advise you without pics....and even with pics very hard to make confident call, being on site is really the only way.

In relation to the use of Trichoderma solutions, yes have used and still use them regularly believe very strongly that they have great potential to be part of a planned regime of soil treatments/drenches to control numerous fungal pathogens and the colonisation of damaged wood tissues....have seen very impressive results.

If it were me I'd be getting comprehensive soil and root analysis done to establish what is there now, and then based on the data determine what is the next step....I would also be planning to used drenches of beneficial fungi along with fungal foods, there are many very good products around many of them very cheap.

But again to repeat just how close you can excavate to any individual tree on one side is determined by the specific growth patterns in the root system of that tree...of course even if the root growth pattern will permit such close excavation there is an enormous amount of remediation and soil improvements to be done over the remaining undamaged root and soil volume to try to balance the damage.

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Sean

Trees are poems that earth writes upon the sky,
We fell them down and turn them into paper,
That we may record our emptiness.
- Kahlil Gibran