Monsanto’s Roundup Ready 2 Xtend crop system and Dow’s Enlist Duo herbicide-resistant seed traits are the next wave of trait technology designed to allow growers to spray herbicides without damaging the crop. The efficacy of these tools, however, could be short-lived if growers rely too heavily on them.
“There are a couple of things I have been telling growers with regard to this technology,” says Dr. Kevin Bradley, state extension weed scientist at the University of Missouri. “One is trait technology is a tool in the toolbox, not a silver bullet. Don’t buy into it thinking it is going to solve everything and all I have to do is spray this herbicide. That won’t work. Second, we have to use the same best management practices we are using now with these future production systems. Those include pre-emergence herbicides, which, in and of themselves, mean multiple modes of action and overlapping residuals as well.”
The companion herbicides to these two new trait technologies, Enlist Duo herbicide with ColexD technology, a premix of new 2,4-D choline and glyphosate, and Roundup Xtend herbicide, a premix of dicamba and glyphosate, use the same two sites of action, Group 4 (synthetic auxins) and 9 (EPSP synthase inhibitor), to manage weeds. Overreliance on the same sites of action can lead to resistant weeds.
Diversifying weed programs with residual herbicides that use different modes of action can preserve the effectiveness of the new seed traits as well as the new herbicide products designed to work with them.
University weed scientists recommend using a pre-emergent residual herbicide followed by a second residual herbicide prior to making the post-emergent application of Enlist Duo herbicide or Roundup Xtend herbicide to manage early weeds and introduce a different site of action. Overlapping residual herbicides reduce selection pressure in weed populations to slow the development of resistant weeds.
Bradley says keeping multiple effective sites of action in play is critical. He estimates that, without the use of pre-emergent residual herbicides or overlapping residual herbicides in combination with these new seed traits, resistance could develop in as few as three to four years.
“It will drive weeds like waterhemp to be resistant to a new mode of action where we didn’t have resistance before,” Bradley says. “That would be unfortunate because the ag industry does not have a plethora of new traits and herbicides coming on the market, so we need to preserve everything that we have.”
In 2016, FMC conducted field trials in Roundup Ready 2 Xtend soybeans to measure the performance of Authority brand pre-emergent herbicides and Anthem MAXX herbicide when used in conjunction with dicamba and glyphosate, the active ingredients in Roundup Xtend herbicide.
Source: www.fmc.com