I’ve this Ailanthus with roots underneath a sidewalk, a concrete drive and a foundation to a garage. What do you know to be the most powerful herbicide on the retail market?
The best treatment seems to depend on the size of the tree and its setting (i.e. if there is any desirable vegetation in the vicinity). One method of control is cutting down the tree and treating the stump with an herbicide (glyphosate a.k.a. Roundup has been used). That’s the ony herbicide I personally have used out of those described in this article. More powerful herbicides might pose more risk of environmental contamination, damage to surrounding vegetation and personal hazard, which is why I suggest you contact your nearest university extension service for advice and consider whether a professional tree service might be best to do the job.
I had an ailanthus adjoining the exterior house wall cut down this spring and it has sent up some sprouts from the stump, so I will probably have to at least try the Roundup route at some point next year.
that is invasive in North America and undesired for the damage it causes.
glyphosate a.k.a. Roundup is a good choice. you may need multiple applications on new growth as it appears from the roots. it is the safest for people to use, least damage to the environment, can be used on many weed types (so you can use it until it is gone).
The safety of Roundup far outweighs any increase in efficacy you might find in another herbicide.