I am going after another collected Surinam Cherry. The root mass needs to be reduced for transport. There is an ant infestation in the root ball. My idea is to treat the tree with a granule ant treatment in lieu of a spray. I feel the chemicals in the spray may be harmful to the roots, thoughts to this approach?
It would depend on which insecticide you are using. Most insecticides today can be applied foliar and root drench. Using something low cost and a short half life like bifen or deltamethrin I would not worry about hurting the roots, it would be the procedure of digging the tree that would induce the stress on the tree. If possible treat the ants a few days before digging the tree.
I had an ant infestation in the root ball of a cherry tree this summer… they were treating the nursery container as a storage for cocoons. I fixed the issue without granules, simply by drenching the root ball in a solution of black soap in water (5% dilution) for a couple of hours, then overnight the next day. They moved out and haven’t come back since.