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Morning Sun
  • NEWS IN AGRICULTURE: Spring musk thistle control

  • We are nearing the end of the time period to control Musk thistles effectively. Musk thistle is primarily a biennial or winter annual species. As a biennial, seed will germinate in the spring and plants remain as rosettes during the entire growing season. Upon surviving a winter, plants will bolt, flower, and produce seeds, taking parts of two growing seasons to complete their life cycle.

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  • We are nearing the end of the time period to control Musk thistles effectively. Musk thistle is primarily a biennial or winter annual species. As a biennial, seed will germinate in the spring and plants remain as rosettes during the entire growing season. Upon surviving a winter, plants will bolt, flower, and produce seeds, taking parts of two growing seasons to complete their life cycle.
    Musk thistle reproduces only by seed. Thus, the goal of any control program is to reduce and/or eliminate seed production. Control options include mechanical, biological, cultural, and chemical methods.
    Mowing at the bloom stage will prevent seed production, but it usually takes two or three mowings at 2-4 week intervals to ensure that musk thistles do not produce seed. Another method to keep musk thistles from producing seed is to cut individual plants 2-4 inches below the soil late enough in the growing season that they don't have time to produce viable seed. The musk thistle head and rosette weevils can also help reduce seed production.
    Cultural control practices are any methods which improve grass vigor and grass cover and would include prescribed burning and good grazing management. Burning by itself will not kill musk thistle but can remove excessive amounts of litter than prevent good coverage when spraying.  Areas with musk thistle should be sprayed about 10-14 days after burning. Proper burning stimulates warm-season grasses that compete more favorably against musk thistle. Proper grazing that maintains and/or improves the vigor of competing vegetation can also help keep musk thistle populations down.
    Musk thistle plants are most easily controlled by herbicides applied during the seedling and rosette stages of growth. Common herbicides such as 2,4-D, dicamba, and picloram are very effective on rosettes. Products containing metsulfuron, chlorsulfuron, and aminopyralid are also effective on musk thistle.
    Once plants begin to bolt, products such as picloram + 2,4-D (Tordon 22K + 2,4-D), metsulfuron + 2,4-D (Escort XP + 2,4-D), metsufuron + chlorsulfuron (Cimarron Plus), metsulfuron + dicamba + 2,4-D (Cimarron Max), or aminopyralid alone (Milestone) or in combination with 2,4-D (ForeFront R&P) are more effective.
    Products containing clopyralid (Curtail and Stinger) provide excellent control of bolted to bud stage thistles. Treat musk thistle before it starts to bloom.
    Always read the label with particular attention to precautionary statements, grazing/haying restrictions, and rates of application.
    For information about this and other livestock and forage topics contact the K – State Research & Extension, Wildcat District office at (620) 784-5337 or email me at rkmartin@ksu.edu  Check out our webpage www.wildcatdistrict.ksu.edu for information about the other services available through Wildcat Extension District.
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