Developing Biological Control of Canada Thistle for Colorado’s Organic Producers Using the Host-Specific Fungus Puccinia punctiformis
Project Director
Dan W. Bean
Year Funded
2018
Award Number
2018-51300-28562
Funded Institution
Colorado Department of Agriculture
Grant Program
OREI (Organic Agriculture Research and Extension Initiative)
USDA NIFA Report (alternate)
Project Overview
Canada thistle (Cirsium arvense) is an invasive, exotic, creeping perennial weed that is extremely difficult to control because fragmenting its deep, extensive root system through tillage can propagate the weed. The rust fungus Puccinia punctiformis is a highly species-specific plant pathogen that can kill Canada thistle by invading its root system.
In this project, the Colorado Department of Agriculture worked with several organic farmers to optimize methods for applying P. punctiformis against Canada thistle and to propagate the fungus for widespread use by organic farmers dealing with this weed. Two farmers and two ranchers participated in the project and observed promising results after inoculating C. arvense rosettes in the fall with powdered, rust-infested thistle foliar tissue. Rust inoculations reduced Canada thistle infestations in one organic orchard and on one beef ranch by >90% over a three-year period.
The project team produced over 100 kg of rust inoculum and distributed it to 61 certified organic producers and many conventional farmers interested in reducing pesticide use.
Farmer Takeaways
(1) The rust fungus Puccinia punctiformis provides effective biological control of Canada thistle. Its effects build gradually over time, with substantial reduction in thistle stem density within one to four years.
(2) Methods for producing and using inoculum to introduce the fungus into a Canada thistle infestation are simple and accessible.
(3) This rust fungus is highly specific to Canada thistle and therefore safe to use as a non-chemical control tactic.
(4) **Note: The availability of rust fungus inoculum through the Colorado Department of Agriculture has been limited to research purposes only for regulatory reasons. Please contact the CO Department of Agriculture for more information.
Project Outputs
Palisade Insectary | Colorado Department of Agriculture.
Canada Thistle Biocontrol | Colorado Department of Agriculture
Current Research | Colorado Department of Agriculture
Dan W. Bean, Kristi Gladem, Karen Rosen, Alexander Blake, Robert E. Clark, Caitlin Henderson, John Kaltenbach, Joel Price, Emily L. Smallwood, Dana K. Berner, Stephen L. Young, and Robert N. Schaeffer. 2024. Scaling use of the rust fungus Puccinia punctiformis for biological control of Canada thistle (Cirsium arvense (L.) Scop.): First report on a U.S. statewide effort. Biological Control 192.