September 15, 2016 | By: | Agronomy,Seed Genetics & Traits

First Step in Weed Management? Identifying Resistance.

Many farmers say they are waiting for new technologies to solve their weed resistance problems. We saw a high rate of adoption for LibertyLink soybeans this year in response to the success of LL beans over the last years and the lack of approval of other traits.

While the weed resistance story has changed drastically in the past five years, my advice remains the same. The information I presented in a 2010 Dakota Farmer article still rings true: “With resistance, the first step is identifying whether you have it. If you are not achieving 100% control of the weeds in your fields, you need to address why. Just five plants remaining per acre in year one can lead to 400 plants per acre the following year. And by year three, there is potential for 32,000 plants per acre to produce resistant seed.”

I talked with a lot of farmers about planting LibertyLink soybeans in 2016. Liberty is the only non-selective herbicide we have available today in soybeans. We’ve worked with the LibertyLink system longer than anyone else in the region – we tested the very first LibertyLink varieties when they were introduced in 2006, and have been testing and growing them ever since.


Farmers must approach weed management proactively rather than reacting to a problem. The management strategy many used was utilizing pre-emerge herbicides in corn and soybean fields because a) early weeds do the most damage to yield, b) a pre-emerge gives timing flexibility with post-applied herbicides, and c) university data has shown yield increases by including pre-emerge chemicals in your program. Another option is tank-mixing other herbicides with glyphosate in your post-applied applications. Dry May/June weather may have reduced the effect of these in some areas but overall the PREs worked pretty well this year.


We need to use PREs in all crops available. Visually, most problem areas are soybeans fields, but I have also noticed many dirty non-soybean crops, which can increase the weed seed bank for said soybean fields. Using companion herbicides adds additional modes of action to your weed management system and helps reduce the spread of these resistant weeds. In addition, this method will bring a reduction in herbicide resistance, prolonging the use of our current effective herbicides.


We expect to have additional soybean options for this next year: Roundup Ready 2 Xtend has received the export approvals it needs and the EPA approval of the herbicide is expected by the end of the year. Enlist and BalanceGT are not too far behind but still lack some export approvals for a full launch. These options most likely will be seed production only in 2017 with a full launch in 2018.

Consider these tips as you’re making your weed management plan and variety decisions for 2017. And as always, contact me with questions.

Adam Spelhaug, Agronomy Lead CCA

Adam Spelhaug

As the agronomy manager, Adam Spelhaug works diligently to determine the best genetics for our region, bringing growers what they need in their fields. Adam has been making his mark on Peterson Farms Seed since 2005. When he’s not discovering genetic breakthroughs, Adam can be found spending time with his family, golfing or bowhunting. He’s a North Dakota State University alumnus, and he’s proud of it. Don’t take any UND green into his office.

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