waterhemp close up


Controlling waterhemp in Enlist E3 soybeans 

waterhemp weed close up 

waterhemp leaf 

Waterhemp is a growing problem for Canadian soybean growers. Often mistaken for redroot or green pigweed, which isn’t surprising since they are all part of the Amaranthus family, common waterhemp has distinctively narrower leaves than those two cousins, and tends to be less hairy, almost smooth in fact.

In 2022, waterhemp biotypes with five-way resistance were documented in four counties in southwest Ontario. Further, throughout the province’s soybean region, waterhemp with three- and four-way resistance is the norm.1

It doesn’t help that the herbicide groups involved (2, 5, 9, 14 and 27) are big hitters, real cornerstones of weed management for corn and soybean growers. And it’s worth noting that, while not in Canada now, Group 4 resistant waterhemp has been found in the United States.2

So why is this happening? There are three main reasons waterhemp is so good at protecting itself against herbicides:

  1. Powerhouse seed production. In a competitive crop environment, one waterhemp plant can produce about 250,000 seeds and, in a non-competitive environment it can produce over a million seeds.
  2. Genetic diversity. Waterhemp requires both male and female parent plants for reproduction (as opposed to self-pollination), which leads to genetic diversity among offspring. That diversity gives waterhemp better odds when it comes to surviving herbicide actives.
  3. Competitive nature. Waterhemp seeds germinate all season long and seedlings grow fast – up to three centimetres per day – giving them greater capacity to outgrow in-crop herbicide treatments.

A two-pass weed control plan is essential for effective waterhemp management. Early weed removal is key to getting the crop ahead of the weed, and in-crop herbicides are necessary to keep late flushes at bay. Waterhemp adapts fast, so ensure you use multiple modes-of-action (MMOA) principles when choosing your herbicides.

Corteva solutions for Enlist E3 soybeans

For EnlistE3 soybean growers, Diligent herbicide provides excellent early season and residual control of waterhemp resistant to Groups 2, 5 and 9. Diligent, a Group 2 and 14 pre-mix, can be soil-applied 30 days prior to and up to three days after planting to ensure fields stay clean through the critical weed-period.

For follow-up in-crop waterhemp control, choose either Enlist Duo herbicide or Enlist 1 herbicide – both are Group 4 herbicides (no waterhemp resistance found yet), and both have Colex-D technology for near-zero volatility and low drift.

  • Enlist Duo herbicide is a proprietary blend of 2,4-D choline (Group 4) and glyphosate (Group 9) for control of most resistant waterhemp biotypes as well as non-glyphosate resistant weeds.
  • Enlist 1 herbicide is a stand-alone 2,4-D choline formulation for in-crop application up to full flower (R2) when tank mixed with glyphosate. For an effective alternative to glyphosate, Enlist 1 can be tank-mixed with Liberty 200 SN, a group 10, up to beginning bloom (R1).

To sum up

Waterhemp’s adaptability and competitive nature means a two-pass weed control plan that includes early weed removal and residual control followed by MMOA in-crop herbicide selections is key. Good resistance management is critical to controlling this weed in soybeans while preserving herbicide efficacy for as long as possible.

1Field Crop News. Exeter/Mount Forest Meeting – April 26, 2022. https://fieldcropnews.com/2022/04/exeter-mount-forest-meeting-april-26-2022/

2Iowa State University Extension and Outreach. Group 4 (growth regulator herbicides) resistance in weeds. https://crops.extension.iastate.edu/encyclopedia/group-4-growth-regulator-herbicides-resistance-weeds#:~:text=First%2C%20this%20is%20the%20sixth,%2C%2014%20and%2027)%201%20.