Canada thistle (Cirsium arvense) is a Eurasian plant which has now invaded widely elsewhere, including here in Canada. This thistle commonly is a host for the bacterial pathogen Pseudomonas syringae, which distorts infected plants, reduces flowering, and makes them turn white. This species of bacterium can affect many plant species, raising the possibility that Canada thistle may act as a reservoir for this disease, which can then spill over to affect co-occurring native plants. In this study I will determine if this is
occurring by surveying native plant populations close to infected thistles showing signs of infection, and by inoculating native species in the lab with bacteria extracted from infected thistles.
Principal Investigator: Peter Kotanen