Unprecedented mortality of the invasive <i>Ailanthus altissima</i> by an indigenous <i>Verticillium nonalfalfae</i> is currently widespread in south-central Pennsylvania where >13,000 trees are dead or dying following inoculation of 65 canopy trees. Because <i>Verticillium</i> spp. cause wilt diseases of many plant species, 64 species were stem-inoculated with <i>V. nonalfalfae</i> isolate VnAa40. Seventeen species exhibited wilt and vascular discoloration following inoculation: Amur corktree, autumn olive, black locust, catalpa, corkwood, crossvine, elderberry, Japanese maple, Norway maple, poison-ivy, redbay, redbud, sassafras, staghorn sumac, striped maple, and tree-of-paradise. However, mortality varied among species with only <i>Ailanthus</i>, elderberry, poison-ivy, striped maple, and sumac exhibiting >50% mortality. Furthermore, natural spread of this fungus within diseased <i>Ailanthus</i> stands was observed only for <i>Ailanthus</i>, devil’s walkingstick, and striped maple. Vascular discoloration, but without wilt or mortality, was observed in 16 inoculated species. Although artificial inoculations provide an evaluation of potential damage to non-target hosts, the low incidence of disease and mortality of these non-target hosts among inoculated <i>Ailanthus</i> offer support that VnAa40 may be host-adapted. Pending the outcome of molecular studies, <i>V. nonalfalfae</i> should be considered as a potential biocontrol for <i>Ailanthus</i>.<p><p>Keywords: Fungus, Trees, Forest Trees
