 Contributed photo
Bouquets of yellow flowers are blooming across our region.
Unfortunately, these colorful blooms are from the poisonous plant known as
tansy ragwort. They have many residents feverishly working to protect their
fields and livestock.
“This year is shaping up to be one of the worst for tansy
ragwort that we have seen,” said Samuel Leininger, WeedWise program manager for
the Clackamas Soil and Water Conservation District (CSWCD). “Weather conditions
this year resulted in perfect conditions to allow these plants to flourish. We
are receiving calls from concerned residents across Clackamas County.”
By the time tansy flowers appear, the best management of
this weed is a good pair of leather gloves and a healthy dose of perspiration
from pulling mature plants. Mowing and cutting do not kill the plants and only
spreads the poisonous vegetation.
Tansy ragwort (Jacobaea vulgaris) has long tormented hay
producers and rural landowners who graze livestock. Horses and cows are
especially susceptible to this poisonous weed.
“The alkaloids in tansy will build up in the liver and cause
irreversible damage in grazing animals,” Dr. Cath Mertens, a local
veterinarian, noted.
“They will generally avoid eating this weed unless there is
nothing else available. The best thing to do is to make sure your horses and
livestock always have something available to eat other than tansy.”
Contaminated hay is also a problem because it becomes
impossible for feeding animals to avoid tansy., “Please pay close attention to
the hay you put up or purchase,” Dr. Mertens said.
In the 1960s and 70s, two insects known as the cinnabar moth
and the tansy ragwort flea beetle were released in Oregon. These biological
control insects have been effective, but they follow a boom-bust cycle.
According to Joel Price, biological control entomologist for
the Oregon Department of Agriculture, “Two years ago the tansy ragwort
population was very high, but the following year the biological control insects
had reduced the tansy ragwort population by 95 percent.”
“With little left for the insects to eat, the insect
populations crash,” Price added. “In a normal year, there would be time for the
biocontrol population to build up. However, the historically wet spring is
causing problems for the flea beetle. This insect overwinters in the ground and
the overly wet spring is keeping it from reproducing quickly enough to help
control this year’s tansy explosion.”
Tansy outbreaks not only poison livestock but also affects
the relationships of neighbors. In Clackamas County, there are no longer weed
inspectors to regulate tansy ragwort, so residents are encouraged to work with
their neighbors to control this weed.
Tansy ragwort is manageable. Residents are encouraged to
focus on areas that are grazed and along fence lines to help prevent plants
from spreading. Flowering plants can be pulled and composted away from grazing
animals or disposed of as trash. Residents are also encouraged to plan for the
coming year to prevent plants from blooming. The Clackamas SWCD has developed
Tansy Ragwort Best Management Practices (https://bit.ly/3RSj8yZ) to help
residents with their control efforts.
“More than ever, we need neighbors working together to
protect pets and livestock from potential poisoning”, Leininger said.
If you have questions about steps you can take, please
contact the Clackamas Soil and Water Conservation District at 503-210-6000 for
more information.
For the Mountain Times by Lisa Kilders, the Education and
Outreach Program Manager for the Clackamas Soil and Water Conservation
District. | 
