Will Second-Generation Herbicide-Tolerant Crops Dominate the Weed Management Toolbox?

Problems triggered by the spread of glyphosate-resistant weeds in corn, soybean, and cotton country continue to worsen. An industry source recently projected that 70 million acres are now infested with one or more glyphosate-resistant weed. The presence of glyphosate-resistant weeds forces farmers to add additional herbicides to their control programs, and apply herbicides more often and/or at higher rates. Costs have risen $25 to over $75 per acre.

photo: United Soybean Board
photo: United Soybean Board

The primary response by the biotechnology-seed-pesticide industry has been to develop a second-generation of genetically engineered (GE), herbicide-tolerant crops that can tolerate direct applications of the phenoxy herbicides 2,4-D or dicamba, in addition to glyphosate, glufosinate, and the “fop” family of grass herbicides. The basic hope is that currently resistant weeds can be controlled, and new ones avoided, by hitting weeds with three or four different herbicide modes of action. But more intensified spray schedules will also increase selection pressure and might hasten the emergence of weeds resistant to multiple herbicides, and this could lead to a herbicide treadmill stuck in hyper-drive.

I have serious concerns about the feasibility of dealing with resistant weeds by doubling down on herbicide use, and agree with the majority of academic weed scientists who are calling for a return to multi-tactic weed management systems that do not depend solely on herbicides. I also worry about the new risks that will arise in the wake of major increases in the volumes of 2,4-D and dicamba applied on corn, soybean, and cotton acreage.

enlist_logoI decided to communicate my concerns, and options to address them, to the EPA. I did so via comments submitted June 30, 2014 to the public docket set up to collect comments on a pending EPA action on the choline salt formulation of 2,4-D developed by Dow AgroSciences. This new form of 2,4-D reduces the risk of volatilization and off-target movement.

My comments were submitted as a private citizen. A few excerpts follow, and the full text can be accessed HERE.

“The pending decisions by EPA and USDA over whether to allow unlimited planting of 2,4-D and dicamba herbicide-tolerant crops will, in all likelihood, be the most consequential to occur over my 30+ year career working on the evaluation of agricultural pest management systems and technology.”

“The decisions will have a profound impact in determining the contents of the farmer’s weed control toolbox in the decade ahead, and whether farmers increase or begin to reduce reliance on a single tactic (herbicides) by adopting proven, multi-tactic weed management systems that virtually all academic weed management experts are now recommending. I strongly urge both agencies to step back and consider the implications of responding to today’s herbicide-resistant crisis by doubling down on what caused it in the first place – excessive reliance on one, or even a few herbicides.”

“If the technologies are approved, EPA and USDA should take several actions to:

  • Reduce the risk of collateral damage,
  • Rapidly detect it, if and as it occurs, and
  • Quickly take actions to prevent the damage from spreading, as it surely would if 2,4-D and dicamba-resistant crops come to dominate corn, soybean, and cotton production to the degree Roundup Ready technology has been embraced by farmers.”

The debate over second-generation, herbicide tolerant crops will no doubt heat up this summer. The final steps in the USDA and EPA approval process are expected this summer, and will almost certainly be followed quickly by litigation striving to overturn the decision, whichever way it goes. So stay tuned, more to come.


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