Musk thistle is a prolific seed producer. Control Optimum germination will take place in moist soil with 59° to 68°F soil temperature in the light and 68° to 86°F in the dark. Musk thistle is an aggressive weed of foreign origin that occurs in pastures, rangeland, roadsides and non-crop areas (Figure 1). Flower heads are deep rose, violet, or purple, or occasionally white. Apply to CSU | Colorado State University, U.S. Department of Agriculture, and Colorado counties cooperating. Wherever you live, Extension’s job is to determine what issues, concerns and needs are unique to each community, and offer sound and effective solutions. Musk thistle seeds are dispersed by wind blown pappus. Learn more about us or about our partners. Musk thistle does not appear to have any spe-cific climatic requirements other than a cool period of vernalization, a minimum of 40 days below 10 °C for flowering. Germination of seed and emergence of seedlings can occur anytime and are correlated with light and moisture. Seeds (achenes) are smooth and hairless. Musk thistle heads are distinguished by their "powder puff" shape. Over 46,000 acres are infested with musk thistle in Colorado (Figure 2). Musk thistle reproduces and spreads only by seed. Bull, musk and plumeless thistle are native to Eurasia and were introduced into North America as seed contaminants. Did you know that mature musk thistle plants die after seed production? Biological control.  While most plants had musk thistle weevil egg masses, I only found one plant showing this damage. Musk thistle (Carduus nutans) is a biennial, although occasionally an annual, in the sunflower family (Asteraceae). Mechanical control.  The adults feed on leaves of thistles, then lay eggs on the heads of musk and related thistle species.  Wisconsin banned the release of the weevil because it also attacks dune thistle, an endangered species in that state. Wind and water are good dissemination methods and seeds are also spread by animals, farm machinery and other vehicles. If hand-digging, dig the root at least two inches below ground level and remove all soil. To combine chemical and biological control methods, apply herbicides when they won’t interfere with insect development. Copyright © 2020 Iowa State University of Science and Technology. Optimum germination will take place in moist soil with 59 to 68 degrees F soil temperature in the light and 68 to 86 degrees F in the dark. Cultural control. Musk Thistle is also known as the nodding thistle. Privacy Statement | Apply herbicides such as Tordon, Milestone, Transline, Perspective, Vanquish/Clarity or 2,4-D to musk thistle rosettes in spring or fall. Several herbicides are registered in pasture, rangeland and noncrop areas to control musk thistle. Seedlings may emerge at any time from spring to late summer and develop a rosette. One or many stems can grow from one root crown. Tordon 22K (picloram), Milestone (aminopyralid), Transline (clopyralid), Perspective (aminocyclopyrachlor + chlorsulfuron), Banvel/Vanquish/Clarity (dicamba), 2,4-D, or Banvel/Vanquish/Clarity plus 2,4-D are commonly used. Our physical location is 1311 College Ave, Fort Collins, CO. Having website issues? Thus, more seeds germinate and establish plants in open pastures and other degraded areas. Musk thistle flowers (Figure 6) and starts to produce seed 45 to 55 days after it bolts. Maintaining pastures and rangeland in good condition is a primary factor for musk thistle management. Musk thistle is a prolific seed producer. To successfully manage musk thistle, prevent seed formation. Life cycle/ other: Biennial growing up to 6 feet tall. Because musk thistle reproduces solely from seed, the key for successful management is to prevent seed production. However, only one-third of the seeds are viable.  While the weevil obviously isn't eliminating musk thistle from the Iowa landscape, I believe its presence reduces thistle populations from where they would be if the weevil wasn't feeding on seedheads. Plants overwinter in the rosette stage until they begin to bolt in mid-March. Each thistle plant can produce 10,000 up to 120,000 seeds. The terminal, or tallest, shoots flower first, then lateral shoots develop in leaf axils. The weevils can reduce seed production by nearly 80 percent, but they are attracted more to early-blooming than late-blooming flowers. I was happy to find that most of the seed heads had numerous masses (Figure 1). 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