Soybean weed control advances

The American Soybean Association sent out a news release dated April 2 announcing acceptance by the Korean Food and Drug Administration of both the Roundup Ready 2 Yield soybeans and Bayer’s LibertyLink soybeans.

This regulatory approval was the final step to allow unrestricted planting in the United States and the importation into all of the major markets.

The Roundup Ready 2 Yield soybeans represent a step up in glyphosate tolerance and the opportunity to develop higher yielding varieties.

High-yielding LibertyLink varieties provide the opportunity to get a completely different mode of action into a soybean program while offering broad spectrum over the top weed control growers have become accustomed to with Roundup Ready.

I believe the introduction of both of these technologies is very significant. While Roundup Ready 2 does not immediately bring anything to the table from a glyphosate resistance management standpoint, it represents a better trait to go forward with. Down the road Roundup Ready 2, as well as glyphosate tolerance technologies from other companies will be stacked with different herbicide tolerance traits that will take weed control to a new level.

LibertyLink soybeans On the other hand, the LibertyLink technology gives growers a chance to have a completely different resistance management program today. I compared the LibertyLink and Roundup Ready technologies in the mid 1990s when they were both in the developmental stage and found them to be very similar. Glyphosate was better on a few weed species and Ignite was better on few different species, but overall they were both excellent.

I also had a chance to work with the LibertyLink technology in the field last year and the performance was a step up from the LibertyLink program we looked at in the 1990s.

Glyphosate resistance should be taken very seriously. Roundup Ready is technology most us never dreamed we would have. It is a serious mistake to take it for granted and assume resistance is something that happens to others but will not happen to you.

Residual herbicides I am concerned that too much emphasis is being placed on just adding a soil residual herbicide to a Roundup Ready program and calling it resistance management. Ken Smith does an excellent job in his talks making the point that “unless the residual herbicide or tank mix partner is capable of providing 100 percent control of pigweed, for example, then those herbicides are not really the answer to resistance management.”

We do not have any preplant or pre-emergence herbicides capable of consistently providing 100 percent Palmer pigweed control. I think residuals should be used in most fields, but they make more of a contribution to overall weed control, preventing re-infestation and perhaps helping delay resistance than they do for managing resistance.

The point is simply if you already have glyphosate resistant Palmer pigweed and you use a residual or even more than one residual and they do not provide 100 percent control, you have a problem.

Residual herbicides have always been inconsistent in Arkansas and always will be. Keep in mind much of the data often shown on pre-emergence herbicides were from plots that were irrigated for activation. This is no criticism of the researcher — I did the same thing when I was doing pre-emergence herbicide plots. However, activation in the real world can be a fickle thing.

I am all about preplant and pre-emergence residual herbicides — use them whether you are in a Roundup Ready, LibertyLink or conventional soybean system. Just be realistic in what you expect from them and remember they have a tendency to be inconsistent.

LibertyLink soybeans provide the opportunity for controlling resistant weed populations and also for prevention. When you combine this technology with a residual program and rotate it with a Roundup Ready program using residual herbicides, you can bring resistance management to an entirely new level.

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TAGS: Management
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