Tackling the Epidemic of Herbicide-Resistant Weeds with Sustainable Solutions

Bookmark and Share

Weeds that have developed resistance to glyphosate herbicide used with Monsanto’s engineered herbicide resistance trait have reached epidemic proportions. A recent survey puts the area infested by these weeds at 61 million acres, and increasing rapidly.

pigweedPalmer amaranth, also known as pigweed, infests a soybean field. Photo: United Soybean Board/Flickr.

Glyphosate resistant weeds have resulted in greatly increased levels of herbicide use, and an estimated 404 million pounds more pesticide (when insecticide savings from Bt GMO crops are counted) than may have been the case without these crops. They make it harder to grow crops, adding substantial expense and reducing yields, and are leading to increased tillage, which reduces soil fertility and leads to soil loss from erosion.

A new briefing paper by UCS, “The Rise of Superweeds — and What to do About It” concisely lays out how these crops are causing big environmental problems, how the seed and pesticide industry’s proposed solution will only make things worse, and how we can resolve this problem sustainably while achieving multiple benefits.

The paper shows that resistant weeds are mainly a symptom of a broken industrial agriculture system, which needs fundamental reform to address not only resistant pests, but also a host of other problems. Proposed solutions that do not recognize these underlying issues will only make matters worse.

In fact, the seed and pesticide industry is set to exacerbate the problem, because waiting in the wings are a new generation of engineered crops resistant to old herbicides like 2,4-D, developed in the 1940s. 2,4-D is a possible carcinogen, and threat to natural vegetation and fruit and vegetable crops due to its high toxicity to those plants and its propensity to drift beyond the soybeans, corn, and cotton it is intended for.

Not Just Your Parent’s Resistance Problem

The science community recognizes that glyphosate resistant weeds are not just another pest resistance problem (which are bad enough), as a few uncritically pro-GMO scientists have suggested. The National Academy of Sciences charged the Weeds Science Society of America with the task of holding a “weed summit,” convened in the spring of 2012, to address the problem, recognizing its severity. Another summit is being planned.

Almost two years later, though, nothing has changed to reduce the epidemic. In a recent meeting hosted by the USDA Economic Research Service on November 8, long-time leading USDA weed scientist Harold Coble said that we are heading for a train wreck, and that technological solutions will result in the same problems as in the past. Other weed scientists concur with this assessment.

Most importantly, it does not have to be this way, because, as the briefing paper shows, cost effective, highly productive alternatives are available. And these alternatives—such as cover crops and crop rotations—combined with minimal tillage and, in non-organic systems, minimal herbicide use, also provide big environmental payoffs.

Cover crops, besides suppressing weeds, can provide nutrients to crops, greatly reduce soil erosion, and increase soil fertility. Crop rotations reduce pest damage and improve yields. So moving to these systems is a win-win solution.

Different from Other Weed Resistance

Some commentators, including some scientists, have tried to downplay the crisis facing farmers. They have noted, correctly, that resistance has been a problem for many years for all chemicals, and even for genetic traits.

But despite the similarities to previous weed resistance, glyphosate resistant crops have exacerbated the problem substantially. And for the same reasons, the new generation of these crops in the pipeline, resistant to other herbicides, will only throw fuel on the fire.

Crops designed to allow an herbicide to be applied without harming the crop initially made weed control easier and more convenient for farmers, giving them more flexibility for when they could spray their crops.

But this advantage led to overuse of glyphosate, greatly increasing the selection of rare resistant plants, and giving them a huge competitive advantage over their susceptible siblings. It’s a case of Darwinian selection on steroids. Without regulations, or other means, to make sure this technology was used wisely, it has instead has become a liability. Without herbicide resistant GMOs, this perfect storm of selection for resistance would not have happened.

It is not a coincidence that this has come about. The industry has lobbied hard against better regulation. USDA has not developed better regulations under the 2000 Plant Protection Act, and has instead been greasing the skids to allow more “deregulated” engineered herbicide resistant crops under older, inadequate, rules. And industry has prioritized research development of these crops because, through patents and contracts and high cost, they have allowed increased control over the seed supply, increased seed costs, and increased herbicide sales. As noted in the new briefing paper, 13 of 20 GMOs in the regulatory pipeline at the time of writing were for new herbicide resistant GMOs.

It is also unlikely that glyphosate-resistant crops would have been made without genetic engineering. Some crops resistant to other herbicides have been developed without engineering, but they have not been nearly as successful as glyphosate resistant crops. And for various reasons, alternatives to engineering, such as mutagenesis, did not work for developing glyphosate resistant crops.

Therefore, in several ways, GMO technology has contributed greatly to the resistant weed problem.

As also analyzed in the briefing paper, the next generation of resistant crops will inevitably lead to weeds with resistance to multiple herbicides. Some weeds resistant to glyphosate already are resistant to other herbicides, and some populations of these weeds are already resistant to 2,4-D or dicamba.

It is only a matter of time before several serious weeds become resistant to all or most of the herbicides available, leaving no good herbicide choices. And, as several weed scientists have noted, there are no new herbicides in the development pipeline. This is the coming train wreck that Coble was referring to.

When in a Hole, First Stop Digging

Meanwhile much of the mainstream weed science community seems unable or unwilling to take effective action, perhaps because of the heavy involvement of the pesticide industry. For example, at the weed summit in 2012, there was essentially no mention of the herbicide resistant crops, poised to be approved, and little evidence since that they will tackle this 800 pound gorilla. If these crops are approved without big restrictions on their use—and given USDA’s record, that seems probable—history is likely to repeat itself with a vengeance.

The resistant weed problem should be a good teachable moment. Much better solutions are available, but also could be improved and made more farmer friendly with the right research agenda at USDA, and the right policies. There is also a need to adapt these practices to local conditions in various regions. This agenda has long been neglected, and this needs to change.

But as long as we are led by the nose by those with a vested interest in the current failing status quo, we will only see things get worse for everyone but the companies that stand to sell more of their products.

Posted in: Food and Agriculture Tags: , , , , , , ,

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.

Support from UCS members make work like this possible. Will you join us? Help UCS advance independent science for a healthy environment and a safer world.

Comments are closed. Comments are automatically closed after two weeks.

5 Responses

  1. Kimberley is missing Ralph’s point altogether….up here in canada we are supplementing our sustainable logging practices with alternative incomes to keep within a sustainable parameter of logging practice….this is ralph’s good point

  2. Kimberly Thiry says:

    Really Ralf when was the last time you ate wind power for supper-sure its low in calories but not very filling. Yes we need to get rid of pesticides and all GMO products but the solution must be realistic

  3. ralf mueller says:

    It is the same issue that plagues humans. Gun violence is fought with the sale of more guns, instead of a gun ban.
    Sale brings profit.
    Sale of gmo, herbicides, insecticides, guns and bombs brings more profit than solving any problem or perceived problem.

    Farmers could think about alternative crops. Maybe harvesting wind and selling electricity could provide some alternative income?1

  4. Claire Robinson says:

    Blast from the past

    I was interested to read Doug’s comment, “Some commentators, including some scientists, have tried to downplay the crisis facing farmers. They have noted, correctly, that resistance has been a problem for many years for all chemicals, and even for genetic traits.”

    I have indeed noticed a tendency by pro-GM people on comments threads on the internet and in social media to suggest that “resistance has always been with us”, and to downplay the contribution that GM crops have made to the issue.

    However, it’s instructive to read Monsanto/Cheminova’s response to regulators during the EU approval of glyphosate, which finally went through in 2002. This can be read in Germany’s draft assessment report on glyphosate, p12 of the pdf here:

    Apparently in response to a regulatory concern about weed resistance, Monsanto writes in 1998: “In 1996 in Australia, it was reported that a biotype of annual rye-grass… was surviving label recommended rates of glyphosate. After examination of greater than 500 samples, only two locations have been confirmed as having the resistant population, indicating the phenomenon is not wide spread [sic.]. Preliminary conclusions drawn to date are that the resistant biotype is easily controlled by conventional practices (tillage, other herbicides), and caused by a complex inheritance pattern, unlikely to occur across a wide range of other species. It should also be noted that glyphosate remains an effective weed management tool in the areas where this resistant population was identified for control of the many other species and cropping systems used there. We thoroughly investigated any alleged incidences of resistance.”

    The UK Pesticides Safety Directorate then commented on the resistance issue in 1999, again in the Germany’s draft assessment report on glyphosate on page 37 the pdf here:

    “It is likely that resistance is low, although there have been two further reports of possible cases in America and Asia. However, there should be a consideration of the risk of resistance developing and a consideration of whether the company should develop a resistance management strategy, particularly in perennial crops or where crop rotation is limited.”

    Clearly, the PSD’s advice to develop a resistance management strategy was roundly ignored by Monsanto, which clung to its claim that widespread resistance was “unlikely”.

    But these passages are also revealing as to the real extent of weed resistance to glyphosate before the advent of GM glyphosate-tolerant crops. By Monsanto’s own judgement, it was apparently rare.

    • Thanks for the detailed comment Claire, I should clarify that when I mentioned pest resistance in the past, I was referring to the general phenomenon. It has been common for many pesticides (and antibiotics). But citing a big problem that has occurred before as support for resistance to glyphosate seems like a pretty weak argument.

      And indeed, Monsanto and others argued that glyphosate was a special case, and that resistance was unlikely for a number of fallacious reasons (obvious in hindsight, but also noted at the time by many skeptical of Monsanto’s reasoning). Not only that, but Monsanto’s dismissal of the problem, and suggested solution (use more, full, recommended amount of glyphosate) only encouraged farmers to do the wrong thing. Overuse of the herbicide is a large part of the problem. This was all documented by a number of academic weed scientist at the time, who severely criticized the company and a scientist that made some of the incorrect arguments.

      Monsanto has done essentially the same thing more recently with resistance to Bt by corn rootworm. It is irresponsible.