NORTH PLATTE, Neb. — Don’t let thistles haunt your pastures this fall! October and early November, is a key time to chemically control thistles in pastures. In Nebraska we have several biennial thistles, but mostly deal with musk, plumeless, Scotch, and bull thistles. Biennials require portions of two growing seasons to flower/reproduce. They develop from seed the first season into a flat rosette. When trying to control biennial thistles, destruction of rosettes prior to flowering (bolting) is an effective means of preventing seed formation and subsequent spread.
Another thistle to look out for is Canada thistle. Canada thistle is a creeping perennial that can be controlled with fall spraying, in conjunction with other management options in the spring. Previous research from Robert Wilson (UNL Emeritus Professor) indicated that control of Canada thistle went from 33%, when an herbicide was applied in the spring, to 90%, when fall applications were made.
While in the rosette stage thistles are more effectively controlled using herbicides. It is important to note that fall spraying of thistles is not a silver bullet and effective control often needs repeated applications. It will take several years of timely control before the soil seed bank is reduced. Choosing the right products for your program is another key step to controlling your thistles. There are many herbicides labeled for thistle control. Note that some products traditionally recommended for spraying thistles have recently changed product names. Take care when purchasing products and always read/follow label directions before use.
GrazonNext® HL, Milestone®, Chaparral®, Graslan® L, Stinger®, Overdrive®, and Tordon 22K® are all products that are labelled for use on biennial thistles as well as Canada thistle. 2,4-D mixed with dicamba is also an effective option, but should be sprayed when temperatures are warmer for the highest efficacy. When using Tordon 22K® or Graslan® L, both products are redistricted use and contain picloram. Use extreme caution around other vegetation, especially trees, as both products will kill woody plants. Most of the herbicides used for control of thistles also kill desirable forbs, so spot spraying individual plants or patches rather than broadcast spraying the entire pasture can spare valuable forbs.
— Megan Taylor, Nebraska Extension
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