Daniel Chichinsky, Kara Hettinger, and Tim Seipel
Department of Land Resources and Environmental Sciences - Montana State University
Cirsium arvense (Canada thistle, creeping thistle, or Californian thistle) is a widespread invasive weed that exists throughout temperate climates of the world. It is difficult to manage and occurs in mountain rangelands, farm fields, along riparian corridors and in natural areas. C. arvense is a rhizomatous perennial herb which reproduces through adventitious shoots and germinating seed. Management has proven difficult because of its extensive rhizomatous root system, in addition to its ability to produce up to 5,000 seeds per stem. In agricultural systems, dense infestations of thistle lead to crop yield loss, harvesting complication and a reduction in crop quality. In natural areas, C. arvense stands can quickly displace native species, changing community composition and decreasing overall biodiversity.
In the MIREN global database, C. arvense was recorded in 7 of the 17 regions, including in Europe, Australia, North America, India, and Armenia. Traditional control methods for the noxious weed include cultivation, competitive cropping, mowing, controlled burns, grazing, and herbicide application. In many of the regions the plant species is problematic in organic cropping systems, especially in soil profiles where tillage cannot be used as the primary means of control. Organic management has proven to be labor-intensive and generally ineffective.
As an alternative, biological controls for C. arvense have been explored for their potential to be incorporated into integrated pest management plans. Many biocontrol agents have proven to be unsuccessful due to their lack of host specificity and varied responses to climate. However, the ongoing exploration of complex ecosystem interactions are providing valuable insight into future integration of biological controls. In Montana, there is current development of a co-evolved fungal parasite known as Puccinia punctiformis. The rust pathogen selectively infects C. arvense and has shown potential to suppress thistle populations in both wild and managed ecosystems. The weed ecology team at Montana State University will assess its functionality across a number of different habitat types including pastures, rangeland, farm fields, and in montane forests. Visit the Montana State University IPM Extension page for more information about the pathogen and our work.