(Kleopow) Borhidi [= Vincetoxicum rossicum (Kleopow) Barbar.] and Cynanchum louiseae (L.) Kartesz & Gandhi [= Vincetoxicum nigrum (L.) Moench]. Can. J. Plant Sci. 85: 243-263. Cynanchum rossicum (dog-strangling vine) and C. louiseae (black dog-strangling vine) are introduced, perennial herbs or small twining vines in the Milkweed family (Asclepiadaceae). Generic placement of these two species has been problematic, but are here treated as members of Cynanchum subgenus Vincetoxicum. The species occur primarily in natural upland areas, including understories of woodlands, pastures, old fields, shores, flood plains and ruderal areas of southern Ontario and Quebec and the northeastern United States. Ecosystems on well-drained, stony soils are often densely colonized, but both species can tolerate a wide moisture regime. Plants establish in full sun or under forest canopies and may form monospecific stands in all light conditions. They often form dense colonies which smother other vegetation and reduce invertebrate and vertebrate biodiversity. Reproduction is by polyembryonic, wind-dispersed seeds. Effective control is primarily by herbicides, since mechanical control is difficult and no biological control agents have been developed. A third European species, C. vincetoxicum, has been reported as an occasional garden escape in southern Ontario and the northeastern United States, but has not yet become naturalized. Information on this species is included because of its close relationship with C. rossicum and its better known biology. DiTommaso, A., Lawlor, F. M. et Darbyshire, S. J. 2005. Biologie des plantes exotiques envahissantes au Canada. 2. Cynanchum rossicum (Kleopow) Borhidi [= Vincetoxicum rossicum (Kleopow) Barbar.] et Cynanchum louiseae (L.) Kartesz & Gandhi [=Vincetoxicum nigrum (L.) Moench]. Can. J. Plant Sci. 85: 243-263. Cynanchum rossicum (cynanche) et C. louiseae (cynanche noir) sont des herbacées vivaces ou de petites vignes exotiques de la famille de l'asclépiade (Asclépidadacées). La déter-mination du genre des deux espèces s'est avérée difficile, mais on a convenu de les classer dans le sous-genre Vincetoxicum de Cynanchum. L'espèce affectionne surtout les plateaux naturels, y compris les sous-étages des boisés, des pâturages, des champs en friche, des rivages, des plaines inondables et des zones rudérales du sud de l'Ontario et du Québec ainsi que du nord-est des États-Unis. L'écosystème des sols rocailleux bien drainés est souvent densément peuplé, mais les deux espèces tolèrent de fortes variations d'humidité. Elles s'établissent au soleil ou sous la canopée forestière, où elles constituent parfois des peuplements monospécifiques, peu importe la luminosité. Leurs denses colonies étouffent souvent les autres plantes et réduisent la biodiversité des invertébrés et des vertébrés. Les deux espèces se multiplient au moyen de semences à embryons multiples dispersées par le vent. On en vient surtout à bout avec des herbicides, car aucun agent de lutte biologique n'a été mis au point et le désherbage pa...

The exotic plant, swallow-wort, a twining perennial of the Milkweed family, has become increasingly invasive in natural areas, successional old fields, and tree plantations on calcareous soils of the lower Great Lakes basin. Because mechanical control strategies are inadequate, swallow-wort's response in natural areas to foliar spray and cut-stem applications of glyphosate and triclopyr was evaluated. Foliar spray applications of glyphosate (3.1 and 7.8 kg ae ha–1) and triclopyr (1.9 kg ae ha–1) were more effective than cut-stem applications of the herbicides (3.1 kg ae ha–1 glyphosate, 1.4 kg ae ha–1 triclopyr). There were no statistical differences in effect among the foliar spray applications. Response to cut-stem application of glyphosate (3.1 and 6.2 kg ha–1) and triclopyr (1.4, 2.8, and 5.6 kg ha–1) in the following year indicated glyphosate to be more effective than triclopyr at all concentrations tested. To effect long-lasting control, all treatments require additional herbicide application.