In article , Nick Maclaren
writes

Oh, come off it! That is scientific nonsense. Depending on what it
was treated with, there is SOME chance of a residue, but that is
small. And then there is another small chance that such a residue
would cause significant damage to plant roots. "Very risky" is
nonsense - the risk is somewhere between very small indeed and nil.

I was thinking more about from what the tree died than with what it had
been treated. Fungal spores can live on in decaying material for ages.
--
Alan & Joan Gould - North Lincs.