LINCOLN — As October approaches and harvest starts, don’t forget about thistles plaguing your pastures.
Fall, specifically October and early November is a key time to chemically control thistles in pastures. More herbicides can be used and the small size of musk thistle seedlings and new growth of Canada thistle is key to effective chemical control. During the season you may have seen thistles in your pastures, if you scout those areas you will most likely find rosettes of musk thistle forming or new Canada thistle growth. While in the rosette stage thistles are more sensitive to herbicides and can be effectively controlled chemically.
There are many herbicides labeled for thistle control. Always read and follow all label directions. The use of tradenames is for educational purposes only and not an endorsement. When choosing your herbicide for spraying thistles, proper identification of the thistles can help make those decisions. Several products are effective across all thistles, but different herbicides have higher efficacies based on the type. For example, Cimaron MAX® is only 80-84% effective on Canada thistle compared to 90-95% effective on Scotch Thistle, so check an efficacy table and your fields before making herbicide choices.
Efficacy ratings show that ForeFront®, Milestone®, Chaparral®, Grazon P&D®, Stinger®, and Tordon 22K® consistently have an 85-95% control response across various thistles. When using Tordon 22K® or Grazon P&D® use extreme caution around other vegetation, especially trees. Both products will kill woody plants. Other products that have good efficacy are 2,4-D mixed with Banvel® or dicamba, but should be sprayed when temperatures are warmer for the highest efficacy. Also Cimaron MAX®, Distinct®, and Overdrive® all consistently have 80-90% control response across various thistles.
Bottom line: if you had thistles this summer and are relying on chemical control, spraying in the fall has more options for control.
— Megan Taylor, University of Nebraska-Lincoln
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