Agricultural Research Service studies on the rust life cycle has enabled the development of methods for getting the fungus to more readily attack the thistle.
ARS plant pathologist Dana Berners has recently reported successful Canada thistle control at 13 sites in the U.S. and abroad, and demonstrated that use of the fungus is safe, effective and economical.
"We know that in weed patches where we have found the fungus that the weed declines," says Bean. "We have found many areas in the state where this is already working."
While researchers still need to understand more about the fungus lifecycle once in the thistle – including how it infects roots which kill the plants – new studies at ARS and CSU are helping unravel how the process works.
"We've known about this fungus for more than 100 years, but only when ARS decided to revisit its potential as a weed control, did they realize this offers some real possibilities," says Bean.
When USDA learned of CSU's extensive work in this arena it decided to fund the grant for more of the state's studies.
Growers are combating Canada thistle today with herbicides – some which offer partial control – and management techniques. Work is also underway in Colorado to evaluate the effectiveness of these methods, which have already revealed that tillage only spreads the weed more, since it breaks up roots into pieces which each can become a new weed plant in the following year.
"We are in the process this winter of bringing together the information we have to get it out to growers and let them know that they have another means to control Canada thistle that mechanical or with herbicides," says bean. " It isn't well known that they can introduce the fungi for control."
For more on this story, see our article in the February issue of Western Farmer-Stockman.