I am growing increasingly concerned over plethora of various invasive species, particularly Tree of Heaven, growing on top of 12’ stone retaining wall.

I am afraid root systems are fracturing it. If so, how can I rid the wall of these? I don’t know that it is possible- or near impossible- to remove entire root system. What can I do to end regrowth or severally limit it. The month is September and in Rhode Island.(Sorry if photo on side!)