Calls it Cynanchum:
https://gobotany.newenglandwild.org/species/cynanchum/rossicum/

Calls it Vincetoxicum:
http://data.canadensys.net/vascan/taxon/10146

Tiebreaker calls it Vincetoxicum:
http://www.theplantlist.org/tpl1.1/record/kew-2898438

See also:
http://plantsoftheworldonline.org/taxon/urn:lsid:ipni.org:names:60456000-2 (calls it Vincetoxicum)
and note from @milkweedguy:
"ITIS [which calls it Vincetoxicum] is the most authoritative source for nomenclature of North American plants. The New Manual of Vascular Plants of Northeastern United States and Adjacent Canada and Flora of North America will both use this nomenclature."