Description:
Plumeless thistle can be distinguished from musk thistle by the leaf-like spines on the stem, and hairs on the underside of the leaf.
Plumeless thistle flower heads are 1-2 inches in diameter, about one-third the size of musk thistle flower heads.Flower heads are solitary at the ends of branches or in clusters of 2-5. Flower bracts are narrowly lance-shaped and appear as sharp spines. Flowers are purplish-pink and clustered in heads that are 1-2 inches in diameter.

• Mechanical: Early spring is a good time to control musk and plumeless thistles when they are in early, actively growing rosette stages. Scout and control the infested area on a weekly basis until you have all the plants killed. Assume there are "escapes" - plants you didn't see the last time. Musk and plumeless thistles are easily controlled in small areas or lightly scattered areas by hand digging or pulling the entire plant. Sever the root at least 1 inch below the soil surface. If the soil is loose or wet, the entire plant is easily pulled. Use necessary protective clothing.
• Biological: Rosette Weevil, Trichosirocalus horridus. A Seed Weevil has been effective in reducing seed production of Musk Thistle in some areas. These insects will slow the spread of the weed, but cannot eliminate an infestation. Plumeless thistle (Carduus acanthoides) is another biennial with similar growth habits and control recommendations as Musk Thistle. Biological controls have been less successful for Plumeless Thistle than for Musk Thistle. Plumeless Thistle is distinguished from Musk Thistle by its smaller flowers, which are born in dusters and are less nodding than flowers of Musk Thistle.
• Herbicide: Refer to the State Noxious Weed Control Board site