Does using GMOs really increase pesticide use?

The Thirteen_Years_cover_2009Organic Center recently released Impacts of Genetically Engineered Crops on Pesticide Use: The First Thirteen Years by Dr. Charles Benbrook, agricultural economist and “Chief Scientist” of the Organic Center. I can’t help but get the feeling that Dr. Benbrook started with a conclusion and found data to fit rather than starting with a general review then finding significant conclusions. It’s not that I necessarily have any specific problems with the information Dr. Benbrook presents, it’s just that I think he’s leaving some key ideas out of the report that should have been considered. There are also generalizations that just aren’t warranted. There are a lot of problems with this report, but I’m particualrly concerned with the way Dr. Benbrook fails, for the most part, to distinguish between different biotech traits, fails to distinguish and between different pesticides, and fails to consider non-biotech traits that could increase pesticide use.

First, all GMOs are not created equal. The two biotech traits currently on the market are herbicide tolerance and insect resistance (Bt). These traits are obviously very different, but most of the report just lumps them together as “GE crops”, even though the report clearly states multiple times that Bt crops have reduced insecticide use. For example:

Bt corn and cotton have delivered consistent reductions in insecticide use totaling 64.2 million pounds over the 13 years. Bt corn reduced insecticide use by 32.6 million pounds, or by about 0.1 pound per acre. Bt cotton reduced insecticide use by 31.6 million pounds, or about 0.4 pounds per acre planted.

Why, then, does the report fail to distinguish between glyphosate tolerant crops and Bt crops when concluding:

For the foreseeable future, this study confirms that one direct and predictable outcome of the planting of GE corn, soybean, and cotton seed will be steady, annual increases in the pounds of herbicides applied per acre across close to one-half the nation’s cultivated cropland base. Farm production costs and environmental and health risks will rise in step with the total pounds of pesticides applied on GE crops.

What about Bt crops? What about nitrogen efficient crops? What about nutritionally enhanced crops? These don’t require additional pesticides of any kind when compared to non-biotech crops. If anything, the conclusion should read:

…this study confirms that one direct and predictable outcome of the planting of herbicide tolerant corn, soybean, and cotton seed will be steady, annual increases in the pounds of herbicides applied per acre across close to one-half the nation’s cultivated cropland base. Farm production costs and environmental and health risks will rise in step with the total pounds of herbicides applied on herbicide tolerant crops.

Second, all pesticides are not created equal. There are huge differences between pesticides in toxcicity, target organisms, amount required, etc. Use of glyphosate, the active ingredient in RoundUp herbicide, certainly does increase with glyphosate tolerant crops. The million dollar question is: does the use of glyphosate replace the use of other herbicides? And even more importantly, what is the relative impact of the herbicides used? The Organic Center’s report doesn’t actually address these questions.
The 2008 report GM crops: global socio-economic and environmental impacts 1996- 2006 (pdf) produced by PG Economics did answer these questions*. They used an index called EIQ (Environmental Impact Quotient) which was first described by Kovach et al in 1992 (to learn exactly how the EIQ is calculated, see the American Farmland Trust’s explanation). The EIQ actually factors in how toxic a pesticide is as well as how much active ingredient is used. This report found (on page 60-61) that, in soybeans, the global impact has been:

In 2006, a 6% decrease in the total volume of herbicide [active ingredient] applied (10.1 million kg) and a 23.7% reduction in the environmental impact (measured in terms of the field EIQ/ha load)

Since 1996, 4.4% less herbicide [active ingredient] has been used (62 million kg) and the environmental impact applied to the soybean crop has fallen by 20.4%.

A similar global impact was seen in maize:

In 2006, total herbicide ai use was 8.3% lower (10.9 million kg) than the level of use if the total crop had been planted to conventional non GM (HT) varieties. The EIQ load was also lower by 10.8%
Cumulatively since 1997, the volume of herbicide ai applied is 3.9% lower than its conventional equivalent (a saving of 46.7 million kg). The EIQ load has been reduced by 4.6%.

It certainly seems strange that two different reports would have such vastly different conclusions.
Third, what about non-biotech herbicide tolerant crops? Breeding for herbicide tolerance doens’t require biotechnology at all – breeders can simply rely on artificial selection (aka “natural” plant breeding). For example, consider the Clearfield trait, resistance to the herbicide imidazoline. Clearfield is available in far more crops than glyphosate resistance, likely because it is not required to undergo any of the additional testing or regualatory hoops that are required for biotech traits. Crops available with Clearfield include sunflower, canola, corn, wheat, and rice. Because this is a non-biotech (non-transgenic, non-GMO) herbicide resistance trait, Clearfield crops aren’t tracked in the same way as Roundup Ready crops.
“This report deals only with GE HT crops” even though “a market research firm recently estimated that non-GE herbicide-resistant crops were planted on roughly 6 million acres in 2007.” The thing is, if biotech herbicide tolerance was never invented, we’d just have many more acres of non-biotech herbicide tolerance. Using herbicide tolerant non-GE crops would result in all of the same effects that we see in GE herbicide tolerant crops. Additionally, improper use of herbicides of any type (in conjunction with herbicide tolerant crops or not) will result in resistant weeds. It is misleading to claim that side effects of herbicide use are due to genetic engineering.
If a person was truly interested in determining how novel traits affect herbicide use, that person would consider all types of herbicide resistance, instead of singling out just the ones created with a certain method.
In sum, these are the three main complaints I have with this report: failure to distinguish between different biotech traits, failure to distinguish between different pesticides, and failure to consider non-biotech traits that could increase pesticide use.
What are your thoughts?
*I already had a copy of the PG Economics report stored in Papers (iTunes for journal articles), but when I went to find the link for this post, I found that PG Economics has actually written their own rebuttal to the Organic Center’s report: Impact of genetically engineered crops on pesticide use: US Organic Center report evaluation by PG Economics (pdf). They cover far more specific issues than I did in this post – I recommend it and the original PG Economics report as a counterpoint to the Organic Center report. No matter our personal beliefs, it’s always good to expose ourselves to many points of view.
Another viewpoint can be found at Truth About Trade and Technology, a non-profit farmer’s advocay group, where Illinois farmer John Reifsteck wrote The Business of Farming in response to the Organic Center’s report.


  1. My favorite random fact is that the biggest insect threat to ag in the midwest crop, the western corn root worm, was controlled with ORGANOPHOSPHATES prior to GM Bt.

  2. Non-genetically engineered herbicide tolerance. Excellent point! I’ve been talking about how herbicide tolerance is just one of many traits that can be generated with genetic engineering, but the reverse genetic engineering is just one of several ways to generate herbicide tolerance is just as true.

    Between that and the point Steve made over at sustainablog that pesticide use is general would have spiked in 2008 anyway because food prices were so high, which means it made economic sense for farmers to spend more money on pest control to get the absolute highest yields possible, I can’t believe this report has been getting so much unchallenged coverage.

  3. Charles Benbrook has known for years that his method of centering on pounds of glyphosate and not EIQ, and excluding the reduction in herbicides used before genetic engineering (nastier herbicides) is misleading at best. Since he is still producing reports using the same narrow-minded approach, I think that his continued exclusion of other lines of evidence and superior analytical methods approaches the ‘dishonest’ category.

    He also curiously suggests that more potent herbicides used in conventional agriculture are better because they reduce the total pounds… but if they are stronger aren’t their environmental impacts more severe?

    Excellent takedown.

  4. Anastasia’s review of Dr. Benbrook’s report is superficial and biased in several ways. The most glaring defect is one shared with the industry-funded PR team of Brookes and Barfoot (aka PG Economics, Ltd) and other biotech industry front groups like NCFAP (see Chapter 6 of Benbrook’s report for a devastating rebuttal to the methods and results of these bogus "simulation studies"). Absolutely no mention, much less discussion, of the major factor driving increased pesticide use with GE crops – an epidemic of glyphosate-resistant weeds triggered by the excessive reliance on glyphosate fostered by Roundup Ready crop systems. The report (Chapter 4) gives a fully documented discussion of this increasingly serious agronomic problem, which has become a major topic of discussion in the agricultural science literature and in the farm press (see pages 34-40 for anyone interested in the truth about this matter). In brief:

    Glyphosate-resistant pigweed (Palmer amaranth) infests millions of acres of cotton/soybean land in the South and is regarded by experts as a major threat to the cotton industry in the South – one impact has been the increase in manual weeding in cotton, something not seen for decades. Resistant horseweed (marestail) is even more extensive, and along with glyphosate-resistant giant ragweed is becoming a huge problem in the Midwest. All told, there are biotypes of nine weed species that have evolved resistance to glyphosate in the U.S. (all but one reported since the year 2000), and collectively they infest millions of acres (this doesn’t even account for weed shifts to glyphosate-tolerant weed species like lambsquarters). It is perfectly clear that these tolerant and resistant weeds are a major factor behind the THREE-fold increase in annual per acre use of glyphosate in cotton, and double the rate on soybeans, since introduction of RR versions of these crops, according to gold standard USDA NASS data on pesticide use (which data, incidentally, are ignored by industry flacks like PG Economics and NCFAP).

    Furthermore, for those in ignorance or denial, glyphosate-resistant weeds are having two other effects, also discussed in the report: 1) Increased use of other herbicides like 2,4-D on soybeans; and 2) A plethora of new HT crops engineered for tolerance to higher levels of glyphosate and/or tolerance to multiple herbicides, including nasty chlorophenoxy herbicides like dicamba and 2,4-D (see Chapter 7 for documented discussion). In other words, the glyphosate-resistant weeds fostered by RR crop systems are deeply shaping the industry’s product pipeline. The report cites a patent issued to DuPont-Pioneer claiming a single plant resistant to anywhere from two to seven or more different herbicides. For those truly concerned with toxicity of pesticides (e.g. Karl Haro von Mogel’s comment on EIQ), these increasingly toxic responses to the rapidly degrading efficacy of glyphosate (over less than a single decade) should be of major concern, as should the strong and growing evidence of the greater toxicity of Roundup formulations with certain surfactants (e.g. POEA) vs. glyphosate alone.

    A look at the evidence shows that this is the true future of agricultural biotechnology – more pesticide-promoting HT crops – rather than the attractive-sounding posterchild crops (the ones endlessly touted in the press that never do come to market, somehow!) so often cited by biased commentators. The fact that the pesticide manufacturers which are also the biotechnology companies focus their R&D efforts on HT crops should hardly come as a surprise. And when the pesticide-biotech firm doesn’t produce the HT crop-associated herbicide, a joint venture works nicely to share the benefits – for instance, Monsanto-BASF collaborating on dicamba-resistant soybeans (BASF is the major producer of dicamba) – once again, documented in the report.

    A few more technical comments. The report does in fact discuss non-GE HT crops, including: 1) That they are planted on roughly 6 million acres, or only <5% of acreage planted to GE Roundup Ready, and are almost all resistant to ALS inhibitors; 2) That the prevalence of weeds resistant to ALS inhibitors (which include imidazolinones) has greatly limited the usefulness and acreage planted to these non-GE HT crops (e.g. Clearfield, STS soybeans); and 3) That one important factor driving adoption of Roundup Ready crops was the prevalence of ALS inhibitor-resistant weeds (notably, common waterhemp in the Midwest, but many many others). This points up nicely the pesticide-treadmill effect of HT crops, whether GE or not. Weed scientists are increasingly concerned by the emergence of multiple herbicide-resistant weeds.

  5. I would like to see the amount of Bt PIP quantified in all of those acres of Bt crops; that would shift the data a bit. The cry toxins are activated and should be counted as such. Should a pesticide not be counted because it is in a plant genetically engineered to produce it? Without that total, all of the numbers about total pesticide usage are inaccurate. Cry toxins have been proven to have an environmental impact and to retain insecticidal properties in the soil and water.

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