Musk thistle (Carduus nutans L.) FamilyFamily: Compositae Description and VariationDescription and Variation: Musk thistle is a biennial plant although it may occasionally act as a winter annual. It is a robust thistle and given the right conditions may grow to six or seven feet tall. The large solitary flowers heads at the ends of the stem are reddish purple. The flower heads droop at maturity. Each plant may have 50 to 100 flower heads with up to 1,000 seeds per head. The seeds do not have a plume or parachute. The stems are spiny and winged except just below the flower head. The deeply lobed, spiny leaves are alternate on the stem. Economic ImportanceEconomic Importance: Musk thistle invades pastures, meadows, and fields. In so doing it crowds out other more desirable forage plants. Livestock will not graze in areas heavily infested with musk thistle thus decreasing available pasture. It spreads rapidly by seed. It also invades streambanks, hindering access, and has been reported as problematic in grain fields. Geographical DistributionGeographical Distribution: Musk thistle is a native of Europe and Asia and has been present in the eastern United States for nearly 80 years. Most western states report some level of infestation. HabitatHabitat: Musk thistle is found in
pastures, rangeland, native meadows, roadsides, forests, stream banks, and occasionally
grain fields. Growth and DevelopmentGrowth and Development: Musk thistle is a biennial plant, occasionally a winter annual. ReproductionReproduction: Musk thistle reproduces by seed that is dispersed short distances by wind. Response to Herbicides: See Pacific Northwest Weed Control Handbook. Read and follow current herbicide labels and recommendations for control. Response to Cultural MethodsResponse to Cultural Methods: Musk thistle may be handpulled or grubbed out. Properly managed pasture will resist musk thistle infestations as long as adjacent infestations are controlled. In cropland situations cultivation will kill young seedlings. Biocontrol PotentialsBiocontrol Potentials: A seed eating weevil, Rhinocyllus conicus is quite effective in reducing seed output. ReferencesReferences: Bultsma, P.M., T.D. Whitson, and F. Lamming. 1991. Comparison of several herbicides applied at different growth stages for control of Canada thistle (Cirsium arvense) and musk thistle (Carduus nutans). In: Whitson, T. and M Ferrell, eds. Rangeland Research and Extension Demonstrations 1991. University of Wyoming Cooperative Extension Service, Agricultural Experiment Station, College of Agriculture. Dunn, P.H. 1976. Distribution of Carduus nutans, C. acanthoides, C. pycnocephalus, and C. crispus in the United States. Weed Science 24:518-524. Fick, Walter H. 1986. Control of bolted musk thistle using clopyralid. Down to Earth. 42:1. Higgins, Robert E. 1977. Musk thistle and its control. University of Idaho Cooperative Extension Publication. Current Information Series No. 20. Ministry of Agriculture, B.C. 1984. Musk Thistle Fact Sheet. Agdex 640. Nilson, Erick B. and Walter H. Fick. 1982. Musk Thistle Identification and Control. Kansas State University Cooperative Extension Publication. Whitson, Tom D. 1987. Weeds and Poisonous Plants of Wyoming and Utah. University of Wyoming Cooperative Extension Publication. |
