Extension doesn't collect this information or recommend particular businesses, but many certified pesticide applicators (those licensed by the MD Dept. of Ag.) should be able to use herbicide to treat Tree of Heaven trees. As the linked page notes (especially in the extensive management information provided by Penn State), the best approach tends to be pre-treatment with systemic herbicide about one month before the tree is cut down, in order to discourage or prevent the rampant regrowth of suckers (new shoots arising from the root system). Both personnel at many landscaping companies and tree companies (and independent arborists) hold a for-hire pesticide applicator's license.

Miri