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Mid-Season Tough Weed: Horseweed (Marestail)

May 30, 2017
This agronomic photo shows horseweed (marestail).

Caption: Horseweed (marestail)

As young corn and soybean plants continue to grow, growers should look out for horseweed (marestail). This annual weed typically germinates in the fall or spring but also has the unique ability to do so year-round.

Purdue University says that crop rotation doesn’t affect horseweed, so knocking down this weed before its highly mobile seeds spread throughout the field offers the best chance of control.

Horseweed is often misidentified as whitlowgrass or a member of the fleabane species, so paying special attention to its characteristics is the key to an accurate diagnosis.


  • Forms a rosette soon after emergence
  • Can grow up to 6 feet tall
  • Leaves decrease in size toward the top of the weed

At this point in the season, applying a post-emergence herbicide can help control horseweed and prevent future seed dispersal. With the increasing threat of herbicide resistance, the University of Nebraska-Lincoln reminds growers to consider choosing a herbicide containing multiple effective modes of action.

Acuron®, Acuron® Flexi or Halex® GT herbicides for corn, and Flexstar® GT 3.5 herbicide for soybeans can help control horseweed and other tough weeds, while also helping manage resistance to herbicides in future seasons.

Ready to scout? Test your weed identification knowledge first by taking the Resistance Fighter® Weed ID Quiz.

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