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tansy ragwort (Senecio jacobaea)
ODA rating: B and T
 
USDA Symbol: SEJA
Oregon tansy ragwort distribution

Other common names
stinking willie, ragwort, tansy butterweed, stinking davies, stinking ninny, tansy ragweed

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Image courtesy of Eric Coombs, Oregon Dept. of Agriculture.
Image courtesy of Rich Old, XID Services.

Image courtesy of Eric Coombs, Oregon Dept. of Agriculture.
 
If images are downloaded and used from the ODA web site please be sure to credit the photographer.

Description
Biennial or short-lived perennial; blooms midsummer to fall. Grows 1 1/2 – 6 feet tall. Leaves dark green, deeply lobed. Numerous seed heads, each with multiple, yellow, multi-rayed flowers. Reproduces by seed only but can all regenerate vegetatively if grazed or mowed and moisture conditions are right.

Impact
Prolific in pastures, clearcuts, and disturbed roadside areas. Tansy ragwort is toxic to cattle and horses, causing irreversible liver damage. Unlike cattle and horses, sheep appear to be unaffected y ragwort's toxicity. They may be either grazed exclusively as a pretreatment to cattle grazing or grazed with cattle. Continuous heavy grazing will prevent flowering and, in many cases, reduce density (Bedell et al. 1981, Sharrow and Mosher 1982). Tansy ragwort’s seeds can lay dormant in the soil for 15 years.  Once considered Western Oregon's most serious noxious weed, biological controls have reduced the severity of outbreaks below economic threshold levels.

Introduction
Senecio jacobaea is native to Europe and western Asia and has become a serious rangeland pest in New Zealand, Tasmania, Australia, South Africa, and North and South America (Baker 1982).

Distribution in Oregon
The first documented site in Oregon was 1922 in Multnomah County and is considered wide spread in western Oregon. Tansy ragwort is still very limited on the east side of Oregon and is under intense management.


Biological controls
Three biological control agents, a seed head fly, a flea beetle and a moth, have been approved for release and are established in Western Oregon. Eastern Oregon plant populations are still sparse and tansy ragwort on the East side of Oregon is being managed for eradication and containment rather than biological control.
 
Botanophila seneciella
Longitarsus jacobaeae 
Tyria jacobaeae