The Royal Horticultural Society considers tree root killers containing glyphosate or triclopyr to be reputable. Products containing these chemicals include Scott's Roundup Tree Stump and Rootkiller and Vitax SBK Brushwood Killer.
Tree root killers should be carefully applied following the manufacturer's directions. In some cases, the person applying the chemical should wear personal protection. Most of a tree's roots can be removed with a mechanical mini-excavator or by hand grubbing. A stump grinder can also be used, although it leaves some roots behind. Attempting to kill tree roots by burning is usually ineffective because of the moisture in the roots.