Agronomy •  2022-02-14

The tools you need to manage herbicide-resistant waterhemp

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soybean growth

Herbicide-resistant waterhemp is a rapidly growing problem for Canadian soybean growers. Once established, waterhemp can be tough to manage because, biologically speaking, it has a lot of tools in its arsenal that help it adapt and thrive, no matter what you throw at it.

There are three tools in particular that make waterhemp such a formidable foe and the king of herbicide resistance: abundant seed production, genetic diversity and a highly competitive growth habit.

More specifically, one waterhemp plant can produce somewhere around 250,000 seeds when growing in a competitive crop environment, and as many as a million seeds or more when not challenged by other plants.

As well, those seeds are genetically diverse from one another; a result of the fact that waterhemp does not self-pollinate and requires both male and female plants to reproduce.

And finally, waterhemp is an incredible field competitor – seeds germinate all season long and grow incredibly fast (2.5 cm to 3 cm per day) – making it a difficult target for herbicides.

Ultimately, herbicide resistance is a numbers game – the more seeds a plant can produce and the greater their capacity for survival, the greater the chance that herbicide resistance will develop. That’s waterhemp in a nutshell. Its ability to survive and adapt is why most waterhemp populations in Canada carry resistance to two or more herbicide groups, including:

  • Group 2, atrazine
  • Group 9, glyphosate
  • Group 5, metribuzine
  • Group 14, PPO inhibitors
  • Group 27, mesotrione (first detected in 2020)


The Enlist weed control system tackles waterhemp

The Enlist™ weed control system, with Brevant® seeds Enlist E3™ soybeans, can be a powerful tool when it comes to effectively managing waterhemp because it brings two new herbicide options to the table. You can choose:

  • Enlist Duo™ a proprietary blend of 2,4-D choline (Group 4 and 9) and glyphosate for control of resistant waterhemp populations and non-glyphosate resistant weeds or
  • Enlist 1 a stand-alone 2,4-D choline formulation (Group 4) that can be tank-mixed with Liberty 200 SN (Group 10) for two modes of action that all waterhemp populations are currently susceptible to.

Both herbicides can be applied from pre-plant up to the R2 stage, so you have the flexibility to go after late flushes of waterhemp. They also contain Colex-D technology for near-zero volatility and low drift – they stay where they’re sprayed.

Brevant seeds Enlist E3 soybeans complete the picture. An advanced seed with high yield potential and robust herbicide tolerance to 2,4-D, glyphosate and glufosinate, Brevant seeds Enlist E3 soybeans are a powerful match against resistant waterhemp, particularly:

  • B091FE (2725 HU): This variety has very good field emergence, multi-race phytophthora resistance (Rps 1C) and above average harvest standability.
  • B191FE (3000 HU): This variety has moderate plant height and a moderately wide canopy along with multi-race phytophthora resistance (Rps 1C and 3A), and strong harvest standability.

Brevant seeds Enlist E3 soybeans paired with Enlist herbicides are powerful tools for soybean growers looking for an answer to resistant waterhemp. This weed is a proven competitor – but that doesn’t mean it gets to win.