Earlier in November, the Environmental Protection Agency placed its seal of approval for over-the-top use of dicamba herbicide in soybeans. That’s good news for soybean growers wanting more weed-control options. But will new dicamba-resistant varieties also be able to boost yields? “New doesn’t always mean it is automatically better,” cautions Shawn Conley, soybean and wheat Extension specialist with the University of Wisconsin.According to Conley, the Wisconsin Soybean Program evaluated 200 Roundup Ready 2 Yield and 47 Roundup Ready 2 Xtend soybean varieties. On average, across all varieties and regions, the RR2Y varieties out-yielded RR2X by 1.8 bu. per acre. That’s significant, he says.
“RR2X soybeans are a stack of herbicide traits and not yield traits,” he says. “These traits protect yield, not enhance yield. Remember this point with all pest-management traits.”Conley recommends using independent trial data and selecting varieties that not only perform well, but also contain the desired traits. That doesn’t mean discounting the threat of resistant weeds, either. Much more than 1.8 bu. per acre could be at stake in vulnerable areas.“I just want to reiterate that every variety must stand on its own as well as remind growers to use multiple modes of action and consider incorporating other traits such as LibertyLink soybeans into your soybean weed management plans,” he says. “All of the data and models I have seen suggest that the dicamba-tolerant crops’ shelf life will be much shorter than the original Roundup if we don’t’ manage this technology correctly.”For more integrated pest and crop management from UW, visit http://ipcm.wisc.edu/.