Biological control of Ailanthus altissima in the United States
Ailanthus altissima (Simaroubaceae: EPPO List of Invasive Alien Plants) is native to Asia. It is a widespread species in the EPPO region where it can invade a variety of habitats including managed and unmanaged grasslands, forests, river/canal banks, rail/roadsides, wastelands, and urban areas. In North America, A. altissima commonly co-occurs with other invasive alien plant species. The wilt pathogen Verticillium nonalfalfae[1] (Sordariomycetes: Plectosphaerellaceae) is native to North America and is proposed as a biological control agent for A. altissima. Its potential as a biological control agent has also been evaluated in the EPPO region (see EPPO RS 2023/214). In 2017, individual A. altissima trees were inoculated with V. nonalfalfae at invaded sites in Virginia (US). This lead to the near eradication of the tree in treated sites. In 2022, these sites were revisited and the plant community was evaluated along with the composition of the soil seedbank. Other non-native species made up a large portion of the plant community and seedbank across all studied areas (treated and untreated sites). The study shows that natural regeneration alone does not effectively restore the native plant community after the use of V. nonalfalfae. Restoration measures should also be conducted to promote native plant regeneration coupled with the control of non-native plant species.
[1] EPPO note: in several European countries (EU member states, Switzerland and the United Kingdom), Verticillium nonalfalfae is listed a regulated non-quarantine pest (RNQP).
Sources
Shively TJ, Barney JN, Reid JL, Salom SM (2024) The bioherbicide Verticillium nonalfalfae effectively removes Ailanthus altissima but leaves many other nonnative plants. Invasive Plant Science and Management, 1-15. https://doi.org/10.1017/inp.2024.27