Controlling an Invasive Tree with a Native Fungus: InoculatingAilanthus altissima(Tree-of-Heaven) withVerticillium nonalfalfaein Highly Disturbed Appalachian Forests of Ohio

Abstract

Highly disturbed forests are commonplace throughout the eastern United States and their residing composition and structure is reflective of their past land use. Management and restoration efforts are complicated by diverse and abundant nonnative invasive plants, including Ailanthus altissima. Verticillium nonalfalfae has been identified as a potential native mycoherbicide option for Ailanthus. To test the efficacy of Verticillium on Ailanthus we designed a study in highly disturbed forests of southern Ohio. At each of five sites, we monitored symptomology, mortality, and rate of spread of stem-inoculated Verticillium on Ailanthus in four inoculated plots and compared it to a control plot. We also monitored native plants for Verticillium symptomology and community responses to Ailanthus control. Our results suggest that Verticillium is an effective tool for controlling Ailanthus with no observed effect on native flora. Further, Verticillium naturally spreads through stands and mortality is slow enough that other resident nonnative invasive plants do not rapidly increase. Study Implications: Managing problematic invasive plants is a costly and time-consuming endeavor that quickly overwhelms resources. The identification and development of native biocontrols will help to suppress invasive plants, especially when considered in conjunction with other control options. Native biocontrols are pests or diseases that are typically nonlethal residents of the local environment but have significant and detrimental impact on nonnative plants. The native fungus Verticillium nonalfalfae along with several other Verticillium species has been identified to kill the invasive Ailanthus altissima. Verticillium can be applied to a subset of Ailanthus stems, and through time, will spread naturally with minimal impact to native species.

Verticillium Species as an Ecofriendly Alternative to Manage the Invasive Tree Ailanthus altissima (Mill.) Swingle

“…Concerning the weaknesses, the host range studies of the American and Austrian group for V. nonalfalfae reported limited susceptible non-target species, comprising ten woody species (among which Aralia spinose L. and Acer pensylvanicum L.; in field), a few horticultural (among which Spinacia oleracea L. and Cucumis sativus L.) and floral species [Petunia × hybrid (Hooker) Vilmorin] [51,53,79,80]. Additionally, even if plants were not negatively affected by the disease, the pathogen was reisolated from artificial inoculated hop, actually classified as one of the main host of V. nonalfalfae, with important economic consequences for brewery companies.…”

“…The isolated strains showed a greater aggressiveness, rapidity of infection and effectiveness [45][46][47], and due to the short life-span of resting mycelium and a rapid host mortality, the opportunities to infect susceptible hosts are very low [48]. Protocols for an easy and effective inoculation were developed and studies to improve the diffusion from diseased plants to healthy ones in inoculated stands were performed, considering that V. nonalfalfae can be transmitted through intraspecific root graphs [49][50][51].…”

Genetic Evidence for Colletotrichum gloeosporioides Transmission Between the Invasive Plant Ageratina adenophora and Co-occurring Neighbor Plants

“…Stricker et al (2016) indicated that the accumulated fungal pathogens suppressed the invasive plant Microstegium expansion [10]. Pile Knapp et al (2022) inoculated a native pathogen Verticillium nonalfalfae to effectively control the invasive plant Ailanthus altissima [11]. On the other hand, however, pathogen accumulation can exacerbate the invasion, because pathogens may cause the increasing diseases on susceptible co-occurring species and indirectly reduce the competitive inhibition of these neighbors to invasive species.…”