Musk Thistle Management
Because musk thistle (Carduus natuans L.) reproduces solely from seed,
the key to successful management is to prevent seed production. Germination
and seedling establishment are correlated with moisture and light. Thus,
more seeds germinate and establish plants in open pastures and other degraded areas.
- Cultural Control: Maintaining pastures and rangeland in good condition.
Do not overgraze. Fertilize only when necessary and according to soil testing recommendations.
- Mechanical Control. Remove plants by severing the roots below ground with a shovel or hoe.
Or mow when the terminal head is in the late-flowering stage. Gather and burn mowed debris to destroy
any seed that has developed.
- Chemical Control. Herbicides registered in pasture, rangeland and noncrop areas to control musk
thistle include:
- Tordon 22K (picloram), Curtail (clopyralid +2,4-D), Banvel/Vanquish/Clarity (dicamba), 2,4-D,
or Banvel/Vanquish/Clarity plus 2,4-D. Apply in spring or fall to musk thistle rosettes before musk
thistle bolts or seed production still will occur.
- Read the Label. You must follow the label directions for all pesticides to get the best results.
Failure to follow labeled instructions may result in poor control, environmental damage, and wasted
time, money and resources. If you have questions, contact a crop consultant, Extension specialist
or County Extension Agent.
- Biological control. The musk thistle seed head weevil, Rhinocyllus conicus, deposits eggs on the back
of developing flowers and covers them with chewed leaf tissue. After eggs hatch, larvae bore into the
flower and destroy developing seed. The seed head weevil reduces seed production by 50% on the average.
Must be used in combination with herbicides or mowing.
- Integrating Control Methods. Apply herbicides when they won't interfere with insect development. Allow the
control insects to complete their life cycle. Or use herbicides in areas that aren't sensitive to their use and
biological control in areas where herbicides are impractical or environmentally unsafe. Cultural methods that favor
desirable plant growth can be combined with chemical or biological control by superimposing proper grazing management
and seeding.
- For more information, contact an Extension Specialist or your County Extension Agent.
Southwestern Noxious/Invasive Weed Musk Thistle Excerpt:
Based on information from George Beck, Extension Weed Specialist, Colorado State University,
gbeck@lamar.colostate.edu
Click the following link to listen to the audio excerpt:
Musk Thistle
Click for problems with the audio file.
| Narrator: One musk thistle plant can produce nearly 70000 viable seeds a year. |
| Bob Ricklefs: So if you allow this plant to go to seed, it will throw seeds for many, many acres and you never know next year where you are going to find the plant. We have a good program of trying to find the rosettes the first year, or the second year, as they come out and spray em. …If we do not catch them then we … spend time with a shovel and they chop them at the ground level. |
| Narrator: To find out more about musk thistle management, contact a state Extension specialist or your
local County Extension Agent. |
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