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Weeds Waking Up: Waterhemp

April 5, 2019

Waterhemp, the next weed in our Weeds Waking Up series, typically emerges in a corn and soybean field over a period of 8 to 10 weeks. While that specific date varies from year to year, it’s likely you won’t see weeds until after your corn has emerged.

Waterhemp is a small-seeded broadleaf weed, and one of the most common weeds found in corn and soybean fields. Like other small-seeded weeds (marestail, Palmer amaranth), waterhemp is a prolific seed producer. Its small, lightweight seeds tend to thrive in minimum and no-till situations, where they can easily germinate near the soil surface or in crop residue.

Unlike large-seeded broadleaf weeds, waterhemp emerges with less plant mass, and its close proximity to the soil surface makes it more susceptible to herbicide applications. The sheer number of seeds it produces, however, makes it difficult to control. Waterhemp plants that are left to go to seed can quickly populate the soil seedbank with millions of seedlings, spreading resistance and ensuring it remains a costly problem for years to come.

Waterhemp facts:

  • Produces up to 1 million seeds per plant.
  • Can grow as much as 1” per day and up to 4 to 5’ in height, with some weeds reaching up to 12’.
  • Pollen can travel a half-mile or more, cross-pollinating other waterhemp plants and spreading resistance.
  • Early-season competition can reduce corn yield up to 15% by the time weeds are just 6” tall.

Learn how to identify and manage waterhemp in this video with Joe Wuerffel, global technical manager in weed control for Syngenta.

Growers can manage waterhemp and protect corn yields by employing multiple, effective sites of action that provide residual control and a start-clean, stay-clean approach to weed management. Acuron® corn herbicide has 4 active ingredients and 3 effective sites of action (Groups 5, 15, and 27). Its atrazine-free counterpart, Acuron Flexi corn herbicide, has 3 active ingredients and 2 effective sites of action (Groups 15 and 27). Both contain the active ingredient bicyclopyrone, which complements the other active ingredients to deliver more effective and more consistent waterhemp control than competitive products. For optimal control, these brands should be applied before waterhemp emerges. Acuron and Acuron Flexi can be applied alone or pre-emergence followed by a post-emergence application of Halex® GT corn herbicide (Groups 9, 15 and 27) plus AAtrex® corn herbicide (Group 5).

Syngenta also offers an effective soybean weed control program that starts with pre-emergence, long-last residual control from Boundary® 6.5 EC herbicide (Groups 5 and 15) or BroadAxe® XC (Groups 14 and 15) herbicide. In addition, a post-emergence application of Flexstar® GT 3.5 herbicide delivers 2 different sites of action (Groups 9 and 14) to manage glyphosate- and ALS-resistant waterhemp.

If you would like input in developing a herbicide program for 2019 based on the specific weed pressures in your field, contact your Syngenta retailer, local Syngenta sales rep or visit www.ResistanceFighter.com.

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