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Getting ahead of pigweeds

A couple of weeks ago I wrote about some of the frustrations some growers were having controlling pigweeds in soybeans and how soil residual herbicides can be inconsistent.

This week I’ll address the other side of the issue and talk about how a lot of growers are much more on top of the pigweed situation. For the most part this year, growers have stepped up and done what had to be done to control them.

We can dream about the good old days all we would like, but the days of controlling a pigweed at any time and any size are pretty much over. If those days are not over on your farm, they will be if you just continue down that path.

There are a lot of good-looking Roundup Ready fields this year. That is a good thing, because we must continue to make this system work. It is just not ever going to be as simple and easy as it once was.

Pigweed control in that system will be determined during roughly the first 14 days before and after planting. The University of Arkansas weed scientists have done an excellent job of delivering the message on the use of residual herbicides and early timing of conventional herbicides in the Roundup Ready system.

I have watched with interest Bob Scott’s pigweed trials in a grower field near Widener, Ark. The University of Arkansas has a field day scheduled there June 29 that you do not want to miss. The pigweed pressure there is at levels found in a lot of areas before Roundup Ready, and a portion of the population is resistant to 176 ounces per acre of Roundup Weathermax.

Through the use of various soil residual herbicides and proper timing of conventional postemergence herbicides, especially Flexstar and Flexstar combinations, there are some very good Roundup Ready treatments in his small plot work. In addition, the grower has followed Bob’s advice and controlled pigweeds much better in his Roundup Ready soybeans than in the past couple of years.

In addition to much better success in Roundup Ready soybeans, LibertyLink soybeans are catching on fast now. A lot of growers this year are seeing the advantages of that system, and some have learned that you can not abuse it either.

The LibertyLink system is as close to “Roundup Ready as it used to be” as you can get, but it has its limitations. Two timely Ignite applications will provide excellent control of pigweed and other weeds. Bob has demonstrated that again in his plots at Widener.

Adding a residual herbicide such as Prefix to the LibertyLink system has advantages from a consistency standpoint and also a resistance management standpoint. The LibertyLink treatment that stands out in Bob’s plots at Widener and also in the grower fields there is Prefix followed by Ignite.

Some growers this year either planted into standing pigweed or simply could not get applications out timely, thinking they could smoke 12-inch pigweeds with Ignite. That is asking too much of the herbicide and that thinking can get this technology in trouble in a hurry.

The LibertyLink system can be simple, flexible and, I believe, the best postemergence option. If, however, you try to make it what Roundup used to be on pigweeds by trying to kill them at any time and any stage, it can fail. Even with the LibertyLink system, you will set the stage for how the season will go during the 14 days before and after soybean planting and emergence. That is simply pigweed control reality now.

This year has demonstrated again that Prefix rises to the top of the soil residual treatments if you can use it without getting boxed in on Flexstar use rates. It fits better in the LibertyLink system than in the Roundup Ready system for this reason.

Some have also learned this year that the pigweed population density can make all the difference in the world how a given herbicide treatment or weed control program can work. I will start here next week.


TAGS: Soybean
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