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Watch for Marestail (Horseweed) In Corn and Soybeans

December 1, 2017
This agronomic image shows the weed marestail, also called horseweed.


Marestail, also known as horseweed, is a small-seeded broadleaf weed that typically emerges in the fall, although it can emerge in the spring and summer months. Like other small-seeded broadleaf weeds, marestail is a prolific seed producer. Since its seeds are small and light, they are easily transferred by wind, animals, human clothing and equipment that is not thoroughly cleaned. While marestail seeds thrive close to the soil surface in reduced-, minimum- and no-till situations, and are susceptible to herbicide applications, the number and mobility with which the seeds spread makes marestail a formidable, tough weed. In addition, marestail can cross-pollinate, further complicating efforts to stop resistance from spreading.

Marestail facts:

  • One of the first glyphosate-resistant weeds identified in U.S. row crops
  • Produces up to 200,000 seeds per plant
  • Seeds are highly mobile and easily spread to new areas
  • Grows up to 6’ tall

Start clean and stay clean throughout the growing season with an application of Acuron® or Acuron Flexi corn herbicides. Acuron has 3 effective modes of action (Groups 5, 15 and 27) and Acuron Flexi has 2 (Groups 15 and 27). Both herbicides contain bicyclopyrone, which is designed to complement the other active ingredients in the premix to deliver broader spectrum, more consistent control of tough weeds other products are missing.

For soybean growers, Syngenta offers effective weed control programs that can start with Boundary® 6.5 EC herbicide (Groups 5 and 15) for pre-emergence marestail control and long-lasting residual.

Visit ResistanceFighter.com to learn more about weed resistance management in corn, soybeans and wheat.

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