GMOs and pesticide use (an email from Greg Conko)

Here is a further Mark Bittman column on GMOs, arguing against GMOs on the grounds that they lead to greater use of chemicals and pesticides.  I would start with quite a simple point, namely to the extent there is a problem with chemicals and pesticides (as there may be with or without GMOs), let’s regulate that problem directly.  Somehow that option is not put on the table as an alternative to what is widely recognized as a rather dubious referendum.  In any case, I posed the question about GMOs and pesticides to Gregory Conko, who has written a book on GMOs, and he responded to me (Greg’s email goes under the fold)…

GC: Note that “pesticide” is a broad term that includes both insecticides and herbicides, as well as fungicides, nematocides, rodenticides, etc. Use of GE crops has had a measurable impact on insecticide and herbicide use, with insecticide use incontrovertibly down and a mixed record on herbicide use. And because there is much more acreage planted with GE herbicide tolerant varieties than with GE insect resistant varieties, herbicide use trends tend to drown out insecticide use trends.  Critics tend to obfuscate these distinctions by using the term “pesticide”, rather than the more specific sub-types, probably because they know casual readers will think “insecticides”.  But even the herbicide data need some additional context.

When measuring raw quantities of active ingredient, you find herbicide use on herbicide-tolerant GE crops to vary widely with crop species and region. In corn, for example, where atrazine is used extensively on non-GE varieties, a switch to Roundup Ready varieties tends to reduce slightly the quantity of active ingredient used, but mainly results in a switch from one to the other chemical. In soy, on the other hand, where herbicides of any kind are used much less frequently in non-GE varieties, a switch to RR soy almost invariably increases active ingredient use significantly.  And because RR soy is by far the most widely grown GE crop (amounting to well over 60 percent of all the soy grown anywhere in the world), on net across all species, this tends to result in an increase in quantity of active ingredient for GE crops generally.

However, merely saying that GE HT varieties result in higher use of active ingredient says little about the environmental or human impact of that change.  Because glyphosate, the active ingredient in Roundup, has close to zero mammalian, avian, invertebrate, etc. toxicity, and biodegrades rapidly, it has a vastly lower Environmental Impact Quotient (EIQ) than the herbicides it’s replacing.  Thus, a switch to RR soy may result in an increase in “pesticide” use while nevertheless being far better for humans and the environment.  Focusing only active ingredient use without any discussion of EIQ is therefore patently misleading.

It’s also worth noting that there is nothing unique about genetic engineering’s ability to produce herbicide tolerant crop varieties. In fact, there are scores of non-GE herbicide tolerant varieties grown all around the world.  A farmer who wants to plant HT canola or rice but doesn’t want to be beholden to Monsanto, or another farmer who’s tired of waiting for full regulatory approval of Roundup Ready wheat or sunflowers, can buy “Clearfield” branded seed from BASF that’s been bred with induced mutagenesis to tolerate the herbicide imidazolinone. Why are GE opponents not talking about imi-tolerant crops? Because they’re not GE. Plant breeders can expose seeds to mutagenic chemicals or ionizing radiation to scramble the plant’s DNA in entirely unpredictable ways and then put them on the market in the United States without reporting to or asking permission from a single regulatory agency, and not a one environmental activist or consumer group will bother criticizing them for doing so. For some reason, skeptics seem to be fixated on the use of recombinant DNA techniques, even though what they criticize publicly are phenomena that occur with all sorts of plant breeding methods.

See here, for example, for a nice critique of the recent study by Charles Benbrook concluding that GE crops increase pesticide use: And a related discussion, with references
to the literature, can be found here:

For a more general discussion of the impacts of GE crops on pesticide use, see:

National Research Council, Impact of Genetically Engineered Crops on Farm Sustainability in the United States, 2010,
” Generally, GE crops have had fewer adverse effects on the environment than non-GE crops produced conventionally. The use of pesticides with toxicity to nontarget organisms or with greater persistence in soil and waterways has typically been lower in GE fields than in non-GE, nonorganic fields. … When adopting GE herbicide-resistant (HR) crops, farmers mainly substituted the herbicide glyphosate for more toxic herbicides.” (p. 3).  And, ” Targeting specific plant insect pests with Bt corn and cotton has been successful, and the ability to target specific plant pests in corn and cotton continues to expand. Insecticide use has decreased with the adoption of insect-resistant (IR) crops” (p.6).

G. Brookes and P. Barfoot, “Global impact of biotech crops: Environmental effects 1996-2009,” GM Crops Vol. 2, No. 1 (2011) pp.
This paper updates the assessment of the impact commercialised agricultural biotechnology is having on global agriculture from an environmental perspective. It focuses on the impact of changes in pesticide use and greenhouse gas emissions arising from the use of biotech crops. The technology has reduced pesticide spraying by 393 million kg (-8.7%) and, as a result, decreased the environmental impact associated with herbicide and insecticide use on these crops (as measured by the indicator the environmental Impact Quotient (EIQ)) by 17.1 %. The technology has also significantly reduced the release of greenhouse gas emissions from this cropping area, which, in 2009, was equivalent to removing 7.8 million cars from the roads.

TC again: In other words, the charge about chemicals and pesticides is not such a strong one.  As we can see from the earlier Indian farmer suicide accusation, the critics are still just clutching at straws.


But isn't a bit bizarre that the 'benefit' of a GMO (one of or some of the successful examples) is we get to dump more neurotoxins on them? As in, for one, it didn't let us not dump neurotoxins on them. It just signals that GMO may not be the bees knees, in fact, just ask the bees. What is the actual benefit versus the perceived future benefit?

Are typical herbicides neurotoxins? At what dosages does that matter?

Paraquat is highly toxic, so much so that it is popular as a suicide agent:

My family used Paraquat on the farm when I was young. We were glad when Roundup came out in the mid-70s, as it was much safer and required fewer doses. Initially the cost was much higher, but it was worth it. Today Roundup is available cheaply in generic form.

Endosulfan is a highly toxic neurotoxin and endocrine disruptor. In the United States, its use is being phased out due to toxicity, but it is still in use. Despite being highly toxic, endosulfan has been widely used for 50 years.


Kindly provide names of the neurotoxins "dumped" on crops because they are a GMO. Can't evaluate how reasonable your assertion is without these names.

The benefit of a GMO with respect to pesticides is either:

1. Increased resistance to existing pests, e.g. corn borers. Result: reduces pesticide use.
2. Increase yields by being able to selectively apply pesticides to pests. Result: increases pesticide use, but switches to a much lower impact compound

I did a lot of pesticide research work recently. You should see the compounds people were using before Roundup. It's the equivalent of belching near pure NOx from a smokestack and suddenly switching to CO2. Neurotoxicity of roundup is basically nil.

Your reference to neurotoxicity is bizarre. Compounds neurotoxic to insects are not necessarily so to humans. Those that are toxic to humans have almost been regulated out of existence; for just one example, just take the carbamate pesticides, used to prevent fungal infections on certain plants and fruits. Although legal to use in the home they have basically been systematically dropped from classification in the US, even though they were once the most widely used (and still the most effective) fungicides for potatoes, asparagus, grapes, corn, and a whole host of other crops.

Since you seem incapable of reading the full article I have taken the liberty to cut and paste the section of the above article that refutes your assertion regarding neurotoxin usage on GE crops:

“Because glyphosate, the active ingredient in Roundup, has close to zero mammalian, avian, invertebrate, etc. toxicity, and biodegrades rapidly, it has a vastly lower Environmental Impact Quotient (EIQ) than the herbicides it’s replacing. Thus, a switch to RR soy may result in an increase in “pesticide” use while nevertheless being far better for humans and the environment.”

Greg Conko's point on herbicides/insecticides is an important one. Roundup is probably as safe a herbicide in terms of toxicity that has ever been developed (lots of home gardeners routinely use it). Secondly, the ability to create herbicide tolerant plants via traditional plant breeding clearly shows as Greg notes, that GMO plants are being singled out for criticism.

Let's not forget that nitrogen-based fertilizers have a huge ecological impact as well.

I'm a little mystified as to TC's implied position on this, which I take to be broadly negative feelings about required labelling of GM foods. Do I understand correctly?

Why is free-market Tyler not in favor of giving the market more information and letting the market decide?

(By the way, this post is an excellent source of information [for the market], and I'm already pointing friends to it.)

The obvious response is: why not let the market decide whether GM foods should be labelled? Is it currently illegal for a manufacturer or distributor of foods to label them truthfully as "GM free"? If it's actually illegal, it should be made legal; if it's not, then there's apparently not enough demand for un-GM'd foods to justify the extra cost of labelling.

The obvious analogy is kosher products. By Dingbat's argument, shouldn't manufacturers be required to label non-kosher foods as such, and allow the public to make an informed decision on the matter?

Gregory has a history/poli sci degreee from American and law degree from GMU, this makes him an expert on GMO's? He works for a corporate front group

Unless you can prove that his actual arguments are wrong, the fact that he had a poli-sci degree originally does not make them wrong. He even went so far as to post his actual sources, which you can examine for validity if you want to.

I am confused as to how the fact that GM-crops are more resistant to herbicides can count as an argument against them?

Isn't resistance to herbicides a positive trait in a crop?

It's a hugely positive trait. It means that you can wipe out tons of species considered weeds much more easily than the old method of having to pull them by hand.

Although I am a total fan of the GM approach and generally impatient with the lack of science in the anti-GM crowd, I have a certain appreciation for their willingness to be stubborn and hold to their criticism, despite everything being against them. As we introduce new technologies we really should have debate about them and make sure we have considered all the angles. In the case of GM the risks in my view are so small and the benefits are so large that you can argue the anti-GM crowd are being "evil" by slowing the adoption of GM in the world. On the other hand, this kind of attitude might be more important in another area, basically the establishment needs watching and we have put up with the negative aspects of this as well as the positive.

Mark Bittman is outside of him area of competence.

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