Look at LL beans as alternative

It wasn’t too many years ago when we were thinking that Roundup was bulletproof. We figured we’d be applying it year after year across most of our acres. We now know that Roundup isn’t bulletproof, and growers all over the U.S. are figuring out how to manage their rotations and cropping plans differently.

There are now more than 10 species of weeds in 22 states with some level of resistance to glyphosate. Resistance in both common ragweed and lambsquarters has been identified in North Dakota. So where do we start in managing this growing problem?

Key Points

• LibertyLink soybean varieties have improved significantly.

• LibertyLink is a sound alternative to Roundup Ready.

• Ten glysophate-resistant weed species now exist.


As northern growers, we have an advantage in watching as our southern neighbors deal with pests and many other crop issues first. If we pay attention, we can learn from them as they develop new tools and strategies to deal with issues like resistance.

With resistance, the first step is identifying whether you have it. If you are not achieving 100% control of the weeds in your RR fields, you need to address why. Was it a coverage issue, a skip, wheel tracks, weather issues or simply surviving plants? If you determine the reason is surviving plants, you have a problem. In year one, just five plants remaining per acre can lead to 400 plants per acre the following year. And by year three, there is the potential of 32,000 plants per acre producing resistant seed. In Arkansas, Palmer pigweed is now resistant to glyphosate, and as you can imagine by these numbers, it has become a major issue.

For 2011, the management strategy we need to embrace is using preemergence herbicides in both our corn and soybean fields. The reasons: Early weeds do the most damage to yield; a preemergence herbicide gives timing flexibility with post-applied herbicides; and university data has shown yield increases by including preemergence chemicals in your program.

Another option is tank-mixing other herbicides with your glyphosate in your postapplied applications. There has been more research done on this lately, and chemical companies have some good options — so talk to your local chemical supplier for recommendations.

The option I am most excited about is adding LibertyLink soybeans to your rotation. There are some excellent varieties available now for our region. They’ve got the genetics to compete with any of the Roundup Ready varieties on the market, and they have the agronomic traits to handle our variable soil conditions. Most of the current varieties have great iron deficience chlorosis tolerance and some soybean cyst nematode resistance as well.

Ignite herbicide for LibertyLink soybeans is the only alternative to glyphosate on the market for complete weed control. I have used Liberty/Ignite since it was first available in the early ’90s with Bt corn. It really has a better fit with soybeans because we are spraying in warmer conditions. And there are tankmix Roundup Ready crops from the previous year, including corn and canola.

I have received some great testimonials on LibertyLink soybeans the past couple of years from growers who have adopted this technology. Consider a management strategy utilizing LibertyLink soybeans as an alternative to the glyphosate-heavy rotation you may currently be using.

Spelhaug is an agronomist with Peterson Farms Seed, Harwood, N.D. Call 866-481-7333 or visit www.petersonfarms
seed.com.

This article published in the October, 2010 edition of DAKOTA FARMER.

All rights reserved. Copyright Farm Progress Cos. 2010.