Woolly distaff thistle (Carthamus lanatus L.) is a yellow-flowered, spiny winter annual native to Mediterranean and central Europe. It has become a problem recently in northern California and southern Oregon. Ranchers in Marin County are reporting populations of distaff thistle so dense that they crowd out grasses and native species. The populations appear to spread along an elevation gradient, maybe along cattle trails.

Organic growers have tried mowing distaff prior to flowering. This sets it back, but is not a long-term solution – not to mention the difficulties of mowing on steep hillsides. In one area, ranchers conducted a prescribed burn in June, which prevented thistle from producing any seed...

Previously in this blog Brad Hanson discussed some of the research Kent Brittan (UCCE Yolo) and I have done with Roundup Ready canola as a crop and then evaluating it as a weed because of its seed dormancy characteristics.  We published an article on the weediness potential of Roundup Ready canola in California this past January in the Journal of Environmental Science and Pollution Research. 

Here's the abstract from the article: 

Abstract:  Canola which is genetically modified (GM) for tolerance to glyphosate has the potential to become established as a new glyphosate resistant weed, thus reducing the effectiveness of glyphosate.  Volunteer from dormant canola seeds produced thousands of plants per acre...

A video entitled, "Alternative Cultivators for Organic Vegetable Production" is now available on YouTube. The video was produced by Aaron Heinrich and Richard Smith and presents information on new developments in automated weed control technology and research information on blind cultivators such as torsion and finger weeders. The video can be accessed at: 
http://www.youtube.com/watch?v=I4kzebMG6rE

For more information on alternative cultivation see the blog below. Also, go to 
http://cemonterey.ucdavis.edu/Vegetable_Crops/Weed_Reports/