Badger thanks for the first hand account, I was wondering too.
It is one nasty plant, and it is pretty sad to see the vast destruction of grass and rangelands it has brought to the Great Basin. It is essentially a spurge monoculture in many places that were previously very productive grassland. Pretty much blankets the entire western Dakotas/ E. MT. We did have quite a bit of success controlling it over the long term using flea beetles that thrive on the weed.
Weeds and beekeepers have an interesting relationship. Sometimes mutualistic, sometimes not. The mutualistic relationships usually conflict with societal desires. For example, in the Cascades Himalayan blackberry is relied upon by beeks and it makes good honey. It also makes impenetrable thickets that will leave you looking like you had been tossed into a barrel of cats when trying to get to that good fishing hole.
In the past, knapweed seeds have been spread from airplanes by CA beeks. We now spend millions of tax dollars trying to manage it.