Seed the First Step in Soybean Weed Control
In 1996, Monsanto introduced Roundup Ready soybeans which completely revolutionized farming practices. In just 3 years, 85% of soybeans grown nationally were Roundup Ready. Glyphosate was the silver bullet that a farmer could count on. But all good things often come to an end. Once glyphosate resistance emerged, it brought yield loss, multiple spray trips, and weedy fields. As weed resistance has grown, specifically in soybeans, farmers have faced more and more difficult weeds to control. We have had several new herbicide traits and stacks introduced into the market, and there will continue to be more added in the next few years. Plus, there are still more in the regulatory approval process. But, these new traits will be making beans tolerant to existing herbicides. While research is underway to find a new mode of action, there is nothing currently in the government approval process. Since this can take over a decade, we must make the best of what we have available today. As you plan next year’s weed management strategy, know the very first decision needs to be seed trait selection.
When discussing seed traits, the first two questions typically asked are: 1. What does it cost? 2. What can I expect for yield? We encourage you to think about it from a program per acre cost. Factor in seed and the herbicide program together. Although the seed on one program may be cheaper, the associated herbicide plan may be costlier, and vice versa.
GT/RR2Y
Glyphosate Tolerant (GT) beans were introduced by Monsanto in 1996 as Roundup Ready™, they are resistant to glyphosate; however, are not resistant to Liberty or any of the other herbicides listed here.
Xtend Flex
This trait is not yet approved. Xtend Flex is glyphosate, glufosinate, and dicamba resistant.
RR2Xtend
Resistant to glyphosate and dicamba herbicides.
LibertyLink
LibertyLink beans are glufosinate resistant but not tolerant of glyphosate. In fact, glyphosate has 90%+ kill factor on LibertyLink soybeans.
GT27LL
These beans are resistant to glyphosate and glufosinate, as well as 4-hydroxyphenylpyruvate dioxygenase inhibitors (HPPD). While resistant, as of this writing there are no herbicide chemistry labels that have a pre-emerge rate for HPPD use.
Enlist E3
This trait is not approved yet. Enlist E3 beans are resistant to glyphosate, glufosinate, and 2,4-Dichlorophenoxyacetic
acid (2,4-D).
SR/STS
Resistant to sulfonylurea and not generally listed in the variety name. It will almost always be stacked with another trait.
From the yield perspective, we have all heard from different companies trying to claim a X.X bushel yield advantage over the other. Many trials were conducted in Missouri that focused on various traits’ yield differences under known glyphosate-resistant waterhemp issues. In 2016, a strip variety trial between LibertyLink, glyphosate-tolerant and RR2X beans was planted before Xtend or Engenia was approved for spraying, but the beans had been approved for planting. Because of the restrictions, they were only able to use glyphosate on the GT and RR2X beans.
With resistant waterhemp present, they tried to control the weeds as best they could by spraying glyphosate and PPO inhibitors. They used three post passes in an attempt to keep the Round-Up and Xtend beans clean. They even did a last-ditch effort of row cultivating. Because of the heavy infestation of resistant waterhemp, they were unsuccessful in keeping the weeds under control. The Liberty beans in the same plot remained clean and out yielded the other two traits by nearly 30 bushels.
A year later a second trial in a different location with known resistance issues was conducted. LibertyLink and Xtend were used again but they were able to use both chemical programs as prescribed. The result was weed-free beans and yields of the two technologies were within a half bushel of each other; all in an 80+ bushel environment. Just as our ProVantage program data has shown in SE Iowa, we believe Xtend and LibertyLink genetics are capable of similar yield results IF there is proper management to maintain weed-free fields.
As you consider your soybean seed trait purchases, keep in mind your herbicide program plans for 2019. Several growers we have talked to let the herbicide dictate seed purchases. We recommend thinking of it inversely; let the seed plan determine the herbicide. If a herbicide can keep your beans weed free, know that the genetics are there to maximize every acre. As a result, our seed offering is built to deliver every trait combination on the market to match your weed management plans. As we approach 2019, we look forward to discussing the genetic options that fit your farm’s herbicide use.