Early in September I wrote about two tansies that occur in British Columbia. Last weekend while at East Sooke Regional Park looking for turkey vultures I found a species of Senecio growing in an old farm field. Tansy ragwort (Senecio jacobaea), like the common tansy, is an introduced plant from Eurasia. It does well in fields, clearcuts and other open areas. This ragwort grows locally on southern Vancouver Island and the lower mainland.
Tansy ragwort is problematic in areas where livestock graze since it contains alkaloids which, when eaten, are made toxic by liver enzymes. Each plant can produce up to 150,000 seeds which remain viable for 20 years.
Several biological agents have been used to try to control tansy ragwort in British Columbia. These include the cinnabar moth (Tyria jacobaeae), a seed head fly (Hylemya seneciella), and the ragwort flea beetle (Longitarsus jacobaeae). It is the beetle that has been most successful as a biological control, particularly in Oregon and California.
For those interested in reading more about the tansy ragwort consider: