I am so sorry that this happened, hortster. I wish you'd tell us the kind of 'discussion' you had with this arborist about this situation, after the damage was obvious.It would be an educational experience for those reading your post to know how it turned out.

MANY trees and other woody plants form root grafts. This is how oak wilt and other diseases are spread. Your arborist has not been keeping up with education, that's for sure. Gosh, the list of trees that form underground relationships is huge. It's the RULE, rather than the exception.

Aspens spread by creeping rootstocks, one tree may cover acres in time - the "trees" in the "grove" all being stems of a single individual, in the manner of a running bamboo, a sumac or an orchard plum.

Here is a link that might be useful: The Myth of Wandering Weedkiller

Could it be that those trees were already in decline?

Around here, birches often die around 20 years of age. Others live until about 40 years old.

Josh

I'm sorry to hear that happened.
It's the reason I try to use herbicide only as a last resort. There's often no turning back.

If there's a bright side to this, it's now some of us know what to try on certain invasives that don't seem to want to die.

The first damage began to occur in less than a week on the closest tree, 5' from the treated stump. At the end of the second week it had completely defoliated. Damage on the remaining trees seemingly settled (no more defoliation) after the third week or slightly longer. I can assure you that the trees were not in any decline before the event; full, rich green foliage, adequate moisture, etc. There is no doubt in my mind that picloram was the culprit with such a rapid demise.
rhizo_1, as to the settlement - it was accepted without debate that the decline was caused by the arborist. The dead trees and dead stems will be removed at no charge, and two new trees will be installed.
Like I said, this arborist made a mistake that I am sure he will never make again, and since I have had years of respect for his ability and good work as viewed through a professional eye, will let it go after the repair.
hortster

Sounds like it was handled very professionally all the way around.

It's amazing what taking responsibility for mistakes does for customer loyalty. Sure it cost him for the new trees and the time to remove the damaged ones but he's got a customer for life now.

Let that be a lesson to us all.

I wish that we could go back to "honor" and drop the greedy "Sue the hell out of them" mentality to just get the problems fixed, fairly. People make mistakes. This guy made an honest one. Wouldn't it be great if we all were perfect like a God? 'Course, we wouldn't be here as humans on this planet...must be in the 7th dimension...
hortster