ENTERPRISE, Ore. — A noxious weed never before seen in Oregon has been discovered in the northeastern corner of the state.
It is a carduus crispis, or welted thistle, which is also sometimes called a curley plumeless thistle.
“It’s never been seen in Oregon before. The nearest it’s ever been reported is North Dakota and British Columbia,” Wallowa County Vegetation Department Manager Ryan Oberhelman said. “That’s an A-List, worst of the worst, thistle.”
Rancher Todd Nash first found the weed and reported it to Oberhelman.
Genetic testing at Oregon State University confirmed its identity. Then Mark Porter, Oregon Department of Agriculture invasive weed management coordinator, and Oberhelman began searching for more of the thistle. They sprayed the edges of Mark Vanderzanden’s alfalfa field where it was discovered, arranged with him to destroy any baled hay up to 15 feet into the field, and walked the irrigation ditch south of Enterprise.
“It’s all along Lower Alder Slope Ditch,” Oberhelman said.
All sites have been sprayed, but Porter and Oberhelman reckon the weed has been in Wallowa County for about four years — and that means it may have gone out in bales of hay to other locations.
The weed warriors, with the assistance of Vanderzanden and other farmers, are tracking down any folks who bought hay from the immediate area to make sure no weed seed traveled elsewhere.
Fortunately, Vanderzanden has excellent records and the weed only appeared at the edge of his field, Oberhelman said.
He said they have no idea how it got here. It most likely started in the ditch, as ditches are common vectors for weed seed.
“Who is bringing in ditch equipment from North Dakota?” Oberhelman mused. “We will probably never know for sure how it got here. But we’ll get in touch with every single person on this ditch system and warn them to watch out for it. We’ll be monitoring this weed for a long, long time.”
The weed is not poisonous to livestock, but grazing is not a reliable control. If it is grazed early in the spring, it will have time to re-flower and spread its seed farther.
“We need to get on top of this thistle because we can,” said Oberhelman. “It hasn’t had time to spread widely and get out of control.”