Never heard that one.

I've never heard of it either. Honeyvine is fine - monarchs have laid eggs on mine, and I've raised them to adulthood on the leaves. The adults were perfect, but it did take more leaves than it does of tropical milkweed/A. curassavica to get the caterpillars through.
Don't get rid of your honeyvine, that's not the poisonous vine, if indeed there really is one.

Sherry

I believe she was talking about Black Swallow-wort as it is commonly called, or Cyncnchum louiseae. It is toxic to Monarch larvae. It is not native, but introduced. and is said to be found in the Northeastern USA, as well as Wisconsin, and California. I recall some discussion on this forum a few years ago.

I'm attaching an article from Monarch Watch about Black Swallow-wort. While it is related to Sand Vine, or Blue Vine, Cynanchum laeve, the latter is not toxic to Monarch larvae. (Think Aristolochia tomentosa versus Aristolochia elegans).

Hope this helps clarify your concerns.

Susan

Here is a link that might be useful: Cynanchum louiseae aka Black Swallow-wort

Yup Black Swallow-wort. There are many Cynanchum species. The ones from Europe are Black Swallow-wort and Pale Swallow-wort (also known as European Swallow-wort). Both are also known as "Dog Strangling vine". I know Black Swallow-wort (C. louiseae) is toxic to Monarchs. They will lay their eggs on it but the caterpillars die when they eat it. Both of these have purple/pink flowers. The native Cynanchum for the most part have yellow or white flowers (some may have light pink). Cynanchum laeve has white flowers and is an excellent host plant for Monarchs.

-Elisabeth

I was reading the Monarch Watch article that Susan linked. Article says that monarchs cannot make it past 3rd instar on Sullivant's milkweed. This is the first time I've ever heard this. I have a patch of Sullivant's. I have more of it than any other milkweed this year. I've found numerous 5th instar cats on it (I bring in cats when I find them but sometimes a cat escapes my detection until it is a 5th instar). I was unable to find another source that questions Sullivant's relationship with monarchs.

Yes, thanks. I guess it has not made it this far south and hopefully never will, but at least you made us aware to be on the lookout.