(Editor’s note: This is the second in a series of articles sharing tips to controlling nine of the most troublesome weeds on no-till farms.)

It's not very hard to find no-tillers in the eastern U.S. who’ve had frustrating run-ins with marestail, also known as horseweed.

Ranked by the Weed Science Society of America as the fifth most troublesome weed for U.S. farmers, marestail is especially tough because its wider germination window means it shows up on the winter annual and summer annual list. And it’s not uncommon for the plants to have both glyphosate and Group 2 or ALS-inhibitor resistant biotypes.

It’s becoming more common for no-tillers to use residual herbicides to control escapes — particularly in Ohio and Indiana, where 6-8 weeks of residual control may be needed to manage spring-emerging marestail.

Bob Bruss, director of technical service for Nufarm Americas, says a contact herbicide will work on marestail when it’s small, but if root systems become well developed and plants are larger, a systemic herbicide is needed.

“With marestail, you want to make sure you kill it the first time around by applying the right product at the right stage, or else it may come back,” he says. “A high rate of products with 2,4-D, dicamba and glyphosate is important, as they all translocate down to the roots and are effective for bigger weeds. And you might consider adding a few other products that add a little residual.”

Weed Behavior 

Marestail is off and running when soil temps…