Distaff Thistle Threatens to Overwhelm West Marin Farmlands The invasive weed, which is injurious to cattle, is a special challenge for organic ranchers who cannot spray, but everyone is affected as the thistle continues to spread. KWMR's Jacoba Charles talks about the problem with Marin Resource Conservation District executive director Nancy Scolari, with organic rancher Sally Gale, and with dairy rancher Dominic Grossi, who heads the Marin County Farm Bureau.