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Hit Canada thistle with herbicides in the fallHit Canada thistle with herbicides in the fall

These Canada thistles are begging for herbicide treatment

Tom Bechman 1

September 21, 2015

2 Min Read

No, the farmer who owns this field didn't leave a perfect gap between two blocks of soybeans and seed Canada thistle. Instead it's an irrigation track where center pivot wheels ran. Thistles were mowed earlier, and they're growing back.

Related: Fall Spraying Of Herbicides Can Nail Winter Annual Weeds

This is one time when it's to his advantage they're growing back. Any time within the next few weeks is a great time to hit Canada thistle with herbicides. You have a better chance of taking them completely out, roots and all, than if you hit them earlier in the season during reproductive stages.


Fall regrowth on non-crop areas – or after a crop if you can harvest early enough – makes a great place to work on thistles. The young plants are actively taking up and transporting materials at this point, and they will transport herbicides absorbed through the leaves down to the roots, where herbicides can work and kill plants.

"Glyphosate is the best option for control and should be applied as late in fall as possible," says Danny Greene, a crops consultant and owner of Greene Crop Consulting, Inc., Franklin. He is also an Indiana Certified Crops Adviser. Currently he is a panelist in Crops Corner and Hoosier Bug Beat in Indiana Prairie Farmer.

You need to spray before the first freeze, however, Greene says. "2,4-D is relatively inexpensive and is another good option," he adds. "Several other products are labeled for Canada thistle control in a corn or soybean crop."

The only sticky wicket may come if you have thistles along a ditch bank that you would like to get rid of. "Use common sense and be aware of regulations concerning spraying ditches," Greene advises. "Do not apply to open ditches with water in them."

On highly erodible land you may also want to use herbicides that are selective against thistles, not non-selective. Glyphosate is non-selective and would kill everything.

About the Author(s)

Tom Bechman 1

Editor, Indiana Prairie Farm

Tom Bechman is an important cog in the Farm Progress machinery. In addition to serving as editor of Indiana Prairie Farmer, Tom is nationally known for his coverage of Midwest agronomy, conservation, no-till farming, farm management, farm safety, high-tech farming and personal property tax relief. His byline appears monthly in many of the 18 state and regional farm magazines published by Farm Progress.

"I consider it my responsibility and opportunity as a farm magazine editor to supply useful information that will help today's farm families survive and thrive," the veteran editor says.

Tom graduated from Whiteland (Ind.) High School, earned his B.S. in animal science and agricultural education from Purdue University in 1975 and an M.S. in dairy nutrition two years later. He first joined the magazine as a field editor in 1981 after four years as a vocational agriculture teacher.

Tom enjoys interacting with farm families, university specialists and industry leaders, gathering and sifting through loads of information available in agriculture today. "Whenever I find a new idea or a new thought that could either improve someone's life or their income, I consider it a personal challenge to discover how to present it in the most useful form, " he says.

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