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Distaff tops noxious weed ‘wanted’ list

By Dean Rea

For the Capital Press

Distaff thistle, Canadian thistle top two problems in the Northwest, experts say.

A spiny character that may stand three feet tall and wears a yellow flower leads Oregon’s “most wanted” list of noxious weeds, says a state specialist who is well acquainted with the suspect.

“The Distaff thistle is probably the biggest threat to pastures, cattle production and serial grains, and it’s tough to get rid of,” says Glenn Miller, an Oregon Department of Agriculture spokesman, who discussed noxious weeds and how to control them during March breakfast meetings of Linn, Benton and Lane county livestock associations.

The thistle, which was first detected in Oregon in 1987, has spread from California into southern Oregon and poses a threat elsewhere in the state if the seeds are spread through hay, cattle and other sources, says Miller, who has 26 years of experience.

Miller characterized the Distaff thistle as “the nastiest thistle on the planet.” While it is located primarily in Douglas County, he says the state will help eradicate the weed anywhere cost-free.

“We don’t have Distaff thistle in Washington,” says Alison Halpern, executive secretary of the Washington State Noxious Weed Control Board. “Canadian thistle is one of our most problematic noxious weed species since it’s prevalent in just about every county in the state and impacts all forms of farming.”

Canadian thistle is hard to control and is a particular problem in irrigated cropland in Eastern Washington, she says. Other weeds that rank high on the “wanted” list are knapweed, yellow starthistle, cheatgrass and tansy ragwort.

Although cheatgrass is not classified as a noxious weed, it creates a problem in cereal grain fields and in rangeland. For livestock producers and dairy farmers in Western Washington, tansy ragwort is a problem.

Native moths, beetles and weevils are among the biocontrol methods of combating some weed problems, as are herbicide applications, Miller told Oregon livestock association members.

Like Washington, the Canadian thistle is a problem throughout Oregon, Miller says. The thistle, which is a perennial, has a complex root system that can form new colonies when cut off or cultivated.

Miller offered advice on how to combat blackberries, a common pest found throughout the Northwest: Mow in the spring, treat in the fall. Use Garlon 3A, 4, Milestone, Capstone, Crossbow.

If treating in early summer or spring, use Garlon 4 in combination with Escort. Apply glyphosate in the fall before it frosts.

If you mow twice, do it once in May and the second time in late August or early September.

Early detection is an objective of the Oregon Department of Agriculture noxious weed program and of the Washington State Noxious Weed Control Board.

Last year Washington embarked on a “Weed ’Em Out” outreach campaign and produced several noxious weed road signs with a new graphic and slogans to place throughout the state.

Oregon is one of the leading states in implementing a biocontrol program.



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