ARS | Publication request: Swallow-wort (Vincetoxicum spp.) biological control update

Submitted to: Proceedings of Northeastern Weed Science Society
Publication Type: Abstract Only
Publication Acceptance Date: November 14, 2011
Publication Date: January 3, 2012
Citation: Milbrath, L.R. 2012. Swallow-wort (Vincetoxicum spp.) biological control update. Proceedings of Northeastern Weed Science Society. p. 81.

Technical Abstract: Pale swallow-wort (Vincetoxicum rossicum = Cynanchum rossicum) and black swallow-wort (V. nigrum = C. louiseae) are herbaceous, perennial, viney milkweeds introduced from Europe (Apocynaceae-subfamily Asclepiadoideae). Both species are becoming increasingly invasive in a variety of natural and managed habitats in the northeastern United States and southeastern Canada, especially New York State, southern New England, and Ontario. Mechanical control has been ineffective. Chemical control can be effective but expensive due to repeat applications, and non-target damage from either approach is a concern in natural areas. Biological control is considered the only long-term control option for swallow-worts. Although little to no damage by arthropods, diseases, or vertebrates has been reported to occur in North America on swallow-worts, some potentially specialized natural enemies of Vincetoxicum spp. are known from Europe. Therefore, identifying host-specific biological control agents appears promising. To date, several potential agents associated with Vincetoxicum spp. have been collected in Europe and Asia. Different species of Chrysochus leaf beetles, which possess a root-feeding larval stage, are potentially quite damaging to the plants, but based on host-range tests appear to present a risk to some native milkweeds. In contrast, defoliating moths in the genus Abrostola appear mostly specific to swallow-worts. However, swallow-wort in open fields is fairly tolerant of defoliation damage, so the moths’ efficacy is questionable. Additional natural enemies have yet to be assessed, such as the pathogen Colletotrichum lineola, a leaf anthracnose, and a seed-pod infesting fly, Euphranta connexa, and foreign surveys are continuing. The recent discovery of the pathogen Sclerotium rolfsii attacking pale swallow-wort in New York may offer potential as a bio-herbicide if it can be demonstrated that this isolate has a restricted host range. Plant demography models are being developed to identify potentially effective guilds of natural enemies, and they may indicate the need for an integrated approach to swallow-wort management.