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Are Genetically Engineered Herbicide-Resistant Crops Undermining Sustainable Weed Control?

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A new article in the respected journal BioScience raises important concerns about the harmful influence of genetically engineered herbicide resistant crops on sustainable weed control. As many others have also noted, the excessive reliance on glyphosate-based herbicides, such as Roundup, has resulted in the emergence and spread of many harmful weeds that can no longer be controlled by glyphosate. These weeds now infest millions of acres of farmland the U.S., resulting in greater herbicide use.

Giant ragweed, one of the serious weeds that have developed resistance to glyphosate. USDA photo by Peggy Greb.

But the new article goes well beyond most previous work by providing insight into the state of weed control for major crops in the U.S., and how the current use of engineered herbicide resistant crops is driving agriculture toward reduced sustainability.

Old herbicides in a new package will cause environmental harm

The authors make several important points to support their thesis. First, because of widespread resistance of several important weeds to glyphosate, companies are now working to commercialize crops resistant to several other herbicides, including the old herbicides dicamba and 2, 4-D. Crops resistant to these two herbicides are likely to be widely used because the herbicides they are immune to are more effective than others. This is bad news, because these herbicides can cause a lot of collateral damage to other crops and nearby natural areas. And natural areas are important for fostering biodiversity, such as pollinators and organisms that control pests and reduce insecticide use.

Based in part on the pesticide/seed industry’s own analysis that both glyphosate and these other herbicides will be used together on engineered soybeans and corn, the authors of the article project total herbicide use to increase more than twofold over the next decade. Dicamba and 2, 4 – D are projected to increase almost tenfold.

And the likelihood of these herbicides moving off site and harming sensitive crops is much higher than for glyphosate—75 to 400 times greater in one comparison, although newer formulations may somewhat reduce this problem.  This spells trouble, especially when combined with several other factors that accompany herbicide-resistant crops, such as use of the herbicides later in the season when nearby susceptible crops and wild vegetation have leafed out and are more vulnerable to damage.

This in turn could lead to a further shift to the few crops that are resistant to these herbicides in an effort to avoid damage.

This kind of further simplification of agriculture is understood to be bad for the environment. And in parts of the country where corn and soybeans are widely grown, it could also impede the growing demand for fresh local foods that have positive effects on jobs.

Where have I heard this before?

Increased herbicide use will surely lead to even more resistant weeds, some with resistance to both glyphosate and 2,4-D or dicamba (or all three), leaving even fewer options for farmers.

The industry has argued to the contrary that it is unlikely that weeds will develop resistance to these herbicides for several reasons…which the article adroitly refutes.

It is troubling that the industry is taking this “head-in-the-sand” attitude because, to the extent it is accepted, it may lead to lax policy by the government and lax practice by growers—that is, too little effort to prevent resistance or to promote sustainable alternatives.

It is particularly troubling because we have heard these irresponsible arguments before from an industry bent on maximizing its sale of products at the expense of the environment. The current article points out how spurious arguments where similarly made that weeds would not develop resistance to glyphosate, where to the contrary, the dramatic increase in resistant weeds is the driving force behind the new crops engineered for dicamba and 2, 4 – D resistance. And I have noted that the industry is also trying to deny and downplay the potential importance of emerging resistance of corn rootworms to Bt.

Undercutting sustainable agriculture

The authors of the new article describe sustainable weed control practices that readers of this blog will find familiar—crop rotation, use of cover crops, crops and cropping practices that effectively compete with weeds, judicious use of tillage, and for non-organic systems, minimal and targeted use of herbicides.

These methods improve weed control and make it more sustainable, while reducing weed pressure.  That means that when herbicides are used, it is less likely that weeds will develop resistance to them. And organic systems, of course, don’t use herbicide at all.

So in the context of these better ways to control weeds, it is perhaps most troubling that the authors document the decline in, as they put it, “…the knowledge infrastructure needed to practice IWM [Integrated Weed Management] in the future…” And, I would add, harm to the research infrastructure that can improve IWM and make it even more efficient.

The authors document a shift in land grant institutions and USDA away from research on more sustainable types of agriculture, toward more emphasis on chemical controls and engineered crops. The dramatic shift of agricultural research funding from the public to the private sector, and the growing ties between academia and the biotech industry, also do not bode well for sustainable agriculture research and infrastructure.

The biotech and chemical industries have no interest in developing the kinds of knowledge- and ecology-based farming vital to a productive and sustainable agriculture that conserves resources and biodiversity, and which will be vital to confronting coming challenges of climate change and increasing population. The companies can’t sell this knowledge, so they are not interested in it.

Sensible solutions

The authors discuss several useful recommendations to make weed management more sustainable. These include mandatory herbicide resistance management imposed by EPA, which approves these chemicals (and I would add, by USDA, which approves herbicide resistant crops); fees on GE herbicide resistant crops and herbicides to discourage their overuse, and which could be plowed back into sustainable ag research; the fostering of partnerships between all stakeholders to develop better stewardship information for farmers and to advise them on sustainable agriculture practices; and more funding and incentives for sustainable agriculture research.

These important policies face a daunting uphill fight—one that UCS and our allies in the sustainable agriculture community will continue to wage. There is considerable resistance to this important agenda by the biotech and pesticide industry and its supporters in the government and academia.

The GE and pesticide industry have no inherent interest in promoting a truly sustainable farming system, and in fact such a system is antithetical to their narrow interests of selling as much herbicide and engineered herbicide-resistant seed as possible. The kinds of sustainable IWM supported in the article would greatly reduce the need for both herbicides and engineered seeds that these companies sell.

Instead, the strong public sector policies advocated by the authors will only come through ongoing and vigorous engagement to convince the public and its servants, who are lobbied heavily by these industries, that sustainable agriculture is critical to the health of our food supply, our environment, and rural communities.

Posted in: Food and Agriculture

About the author: Doug Gurian-Sherman is a widely-cited expert on biotechnology and sustainable agriculture. He holds a Ph.D. in plant pathology. See Doug's full bio.

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3 Responses

  1. Dan Barth says:

    Here in central Wisconsin the commercial ag fields are required to post danger, keep our warning signs to the heavy use of pesticides. These are the fields wherein the beans, peas, sweetcorn, pickles and potatoes that wind up on our nation’s grocery store shelves are grown. How insane it seems to me that the land we grow our food on is officially deemed dangerous to living beings. This is why I garden.

  2. Amy Mortensen says:

    I am thankful that the Union of Concerned Scientists are the voice of reason. They have dedicated their precious time, effort and energy to shed light on an extremely important issue -the impact of herbicide resistant crops on our current and future food source. I have been a member of a community garden for 20 years, and our guiding principle is “NO CHEMICALS”. We manage to grow our food in plots buzzing with bees and abundant vegetables.
    Thanks to my brother David and to his fellow researchers for their persistence, for spreading the word, and for standing up to the so called conventional wisdom as the voice of reason. So very much appreciated. Perhaps the EPA ought to make this article mandatory reading. I am forwarding this article to my fellow community gardeners as I know they will appreciate this good work as well.

  3. Karen Clegg says:

    What a comprehensive and readable article. Isn’t that fundamental for all of us, our food! My brother, David Mortensen was one of the authors of the article. I sent you article on to many people to help them become aware. Hey, I hope the President had this article. Well done!
    Sincerely,
    Karen Clegg