Aculops ailanthi are vagrant eriophyids that live on the surface of leaves (as opposed to forming galls or seeking other forms of protection) and can build up large populations on Ailanthus that cause leaf deformation, yellowing, necrosis, premature leaf drop, and death in young, container­-grown trees. The majority of the mites are found on the underside of
leaflets but are occasionally found on the upper side of leaflets and even on the stem when mite
populations are large.