How do you kill ailanthus in Altissima? Apply herbicide via aerial or broadcast foliar spray, basal bark spray, cut stump, or injection method. Avoid desirable tree species, if present. Wilderness, other natural areas, and/ or small infestations Remove very young seedlings by hand; most effective in loose, rain-moistened soils. Why is Ailanthus altissima bad? Ailanthus can create dense clonal thickets, almost monocultures. It grows very quickly, often displacing native plants, which may affect wildlife. It is extremely difficult to eradicate, and cutting down the trunk and/or pesticide treatment only result in new shoots growing up from the roots. How do...