Get with the Program: Controlling resistance management with a Program Approach

Written by Dave Harwood 
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close up of soybeans

I’m sure I’m not the only one who’s noticed that weed control in soybeans has become more complicated over the years.

On one hand, issues like herbicide resistance have become a bigger challenge. It’s not uncommon to find weed populations with resistance to more than one mode of action or a field where one weed species is resistant to glyphosate, say, and a different weed species is resistant to imazethapyr. It certainly makes herbicide selection a bit tricky.

But on the other hand, we have far more information than previous generations ever had about weed biology, how weeds and crops interact, and how certain management strategies can have direct outcomes on yield.

Take the whole concept of early weed control in herbicide-tolerant soybeans. It really wasn’t that long ago when it was considered good practice to wait until most weeds had emerged before spraying. Today’s farmers would never let weeds get that big.

That shift in thinking came from countless studies showing that there’s  a critical weed-free period and that the presence of even small weeds during this period can cause yield loss. And we’re talking a lot of yield here. Long-term data collected by Peter Sikkema1 at the University of Guelph shows that weed interference in soybeans can result in yield losses of up to 36 per cent.

It’s also why many soybean farmers have changed their weed control strategy from a one-pass, purely post approach to a two-pass pre and post approach – there’s an ROI to be had.

We’ve learned a lot over the last decade or so about how herbicide resistance develops in weed populations and how a well-managed pre- and post-emergence herbicide program can help control resistant weeds as well as delay the onset of further resistance.

This is where I think the Enlist™ weed control system has something really valuable to offer.

Enlist E3™ soybeans are equipped with multi-mode of action herbicide tolerance to  2,4-D, glyphosate and glufosinate.  The program approach is about using multiple practices to protect the technology into the future  to help deliver high yielding, high quality soybeans.

And what’s really exciting to me and an opportunity for soybean growers in Canada is the Enlist system is 100% enabled for post-emergence applications of group 4 Enlist herbicides and group 10 Liberty.  Enlist herbicides don’t have a temperature restriction so E3 soybeans, unlike some other herbicide tolerant systems allows growers to take full advantage of the technology. In fact, with the Enlist™ 1 and Liberty® 200 SN tank-mix, it’s better to spray when it’s hot and sunny as you’ll get better product performance without the worry.

So, what is the program approach?

  1. Pre-plant. Apply a pre-emergence residual herbicide with different modes of action. Something like Diligent™ herbicide, a Group 2 and 14 blend that tackles glyphosate resistant weeds like waterhemp early.
  2. In-crop. Apply Enlist Duo™ or Enlist 1 + Liberty 200 SN post-emergence for excellent control of late emerging and flushing weeds to protect yield and have a clean harvest. The Liberty is a group 10 adding more diversity to keep weeds off balance.

What’s the difference between the Enlist herbicides? For me, it comes down to grower preference and how customized you want to build your program.  Enlist Duo makes it easy by providing a premix with glyphosate so it’s very user friendly.  Enlist 1 on the other hand is the new stand-alone version of 2,4-D choline which allows you to pair it with your glyphosate and customize rates and ratios.  And if you’re tackling some heavy populations of resistant weeds like waterhemp, it’ll allow you to match the Enlist chemistry with Liberty 200 SN so you’ll have 2 effective modes of action working for you.

But what is truly unique about both Enlist herbicides is that they come with Colex-D™ technology for near-zero volatility and low drift. We’re talking significantly lower with 90 per cent less drift than traditional 2,4-D and 96 per cent less volatility than 2,4-D ester. This is a game-changing technology for growers because these herbicides are predictable.  They are fully enabled for the post-emergence window so there is an excellent opportunity with E3 soybeans to use a group 4 herbicide to manage against resistance as well as get ahead of some of the more challenging perennial weeds.

That’s critical when you think that a lot of soybean country is also fruit and vegetable country. Knowing that your herbicide is going to stay where it’s sprayed and not harm other crops is incredibly important. You can learn more about application best practices in our Product Use Guide to ensure you are always observing good product stewardship and following all label precautions.

Managing for resistance and getting resistant weeds under control is definitely a challenge in soybean production today. I truly think that the Enlist weed control system and the program approach offer an effective resistance management strategy that helps farmers keep fields clean while protecting yield potential.

The Enlist weed control system is helping Canadian farmers meet the challenges of farming today, hear what real soybean farmers have to say about their experience with the Enlist at

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