Killing Tansy?

[jka300]

I am looking for solutions for killing tansy. In the last 2 years the darn stuff has just exploded in our pastures. I tried talking to our county about it since it did come from their gravel pit but they said it is my problem now, really nice of them right. If someone could throw some ideas my way I would be much appreciated.
Thank you.

 

[Alberta farmer]

Tansy needs to be sprayed before it flowers. Once you see the yellow buttons you might as well forget about it until later in the year. In late August Tansy seems to be susceptable to spray once again.
Grazon or Tordon 22K work well before flowering and Remedy works well later in the year. Just my experience.