Fall Thistles and Pasture Seeding

With everything to get done in the fall, low on the priority list might be planning for pasture improvements next year and weed control.  However, some time spent on these topics this fall could pay dividends next year.

First, October and early November is an ideal time to control thistles in pastures.  Most of our thistle species in the state fall into two categories, biennales or those that grow over two seasons and perennials, those that come back year after year.  Biennial thistles like musk, plumless, scotch, and bull growing now are new plants that grew from seed this year and are forming 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. Fall herbicide applications on perennial species deplete energy reserves and stress the plant as we head into winter.  This weakening when maintained for several years, paired with spring control to prevent seed production can slowly shrink even hard to control Canada thistle patches over time.  Just like their biennial cousins, this time of year, Canada thistles will also be primarily in a low growing vegetative form.

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 to the point that new plants stop sprouting.

When it comes to treatment options, there are many herbicides labeled for thistle control. Take care when selecting a product that grazing or harvest restrictions meet your operational plans and that you are picking the correct product.  Some products traditionally recommended for spraying thistles have recently changed product names, so keep an eye on the active ingredients to make sure a change in name doesn’t also mean a change in action.

Some options to consider are 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.  Tordon 22K® or Graslan® L, are both restricted use products containing picloram.  Use extreme caution around other vegetation, especially trees, as both products will kill woody plants.  

After we get weed problems under control, those looking to do pasture improvement next year by either reseeding or interseeding may want to start planning their projects now.   If frost seeding is an option being considered, having seed available when a window of opportunity presents itself (cold temperatures with little snow cover), can make taking advantage of the weather more timely.  Additionally, those considering a spring interseeding of legumes can start preparing the site in the fall.  Competition from surrounding grass plants is one of the biggest hurdles preventing a good stand of interseeded legumes in a pasture.  By grazing heavy this fall, grass vigor can be lessened in the spring, giving planted legumes a chance to get up and growing before being outcompeted by their neighbors.

Fall is a busy time, and proper pasture management doesn’t help lighten the load.  Even so, time spent controlling thistles this fall can reduce work in the future. For those planning on renovation or seeding projects, work now can lead to success in the spring.

-Ben Beckman is a beef systems Extension Educator serving the counties of Antelope, Cedar, Knox, Madison and Pierce.  He is based out of the Cedar County Extension office in Hartington.  You can reach him by phone: (402) 254-6821 or email: ben.beckman@unl.edu