Can you recomend any products for controlling root suckers on a small ornamental apple tree?
Root Sucker Chemical Control
Any chemical that one would use to control the root suckers would almost certainly wind up effecting the main roots of the tree. Thus a chemical is really not the way to go. The best thing you can do is to cut the root sucker out as far down and back towards the tree as you can and place some Elmers regular white glue on the end of it, not the school glue but the regular kind. Let it set of a few minutes and then cover back over with soil. The glue will sometimes help prevent off shoots from the same area that brought forth the root sucker. Does not always work in very hardy trees and shrubs but is worth a try.