What does a GMO label tell you about herbicide use?

There has been quite a bit of discussion lately about various food companies deciding to label their products for GMO content in response to Vermont’s GMO labeling bill. I’m still mostly indifferent to GMO labels, and frankly, have grown tired of this particular debate. But there seems to be at least one misconception that I wanted to briefly address. If you follow the GMO issue at all, you’re probably aware that a large majority of GMO crops currently being grown are herbicide tolerant. In 2015, 89% of corn and cotton, 94% of soybean, and 100% of sugarbeet in the US were genetically engineered to have herbicide tolerance. A very large majority of herbicide tolerant crops are Roundup Ready, which makes them tolerant to the herbicide glyphosate. This allows farmers to spray glyphosate, better known as Roundup, to the field without causing damage to the crop.

All crops are herbicide tolerant

Herbicide tolerance is, by far, the most dominant GMO trait on the market. This has led at least some people to believe that non-GMO products are less likely to have been sprayed with herbicides. This is simply not the case. Long before we had GMO varieties, we were already spraying herbicides on those same crops. That’s because nearly all crops are naturally tolerant to a variety of other herbicides; no genetic engineering required. The figure below shows USDA data on the percentage of corn, soybean, and cotton acres in the US that were sprayed with herbicides between 1980 and 2010. Around 96% of all three crops were sprayed with herbicides before the introduction of any GMO crops, and that value didn’t change after adoption of GMO crops.


The bottom line here is that a GMO label will not give any indication of whether the product has been sprayed with herbicides, because non-GMO crops are also highly likely to be sprayed with herbicides (albeit a different set of herbicides). The exception to this would be crops produced organically. Although organic farmers commonly use various other types of pesticides, there are no herbicides registered for use directly on organic crops.

NOTE: my weed science colleagues will almost certainly be annoyed with me for calling GMO crops herbicide tolerant rather than herbicide resistant. The Weed Science Society of America has distinct definitions for these terms, and by those definitions, Roundup Ready (and Liberty Link) crops would be considered herbicide resistant, not herbicide tolerant. However, this distinction is largely irrelevant to the public discussion, so I stuck with the terminology that is more commonly used by both the public as well as the USDA when discussing this technology. 


  1. Labelling of GMOs is bogus because it does not say anything about quality or potential health risks. You may as well label if the crops were harvested by Moslems, Jews or Hindus.
    Interestingly, a petition by scientists to have everything derived from GMOs lebelled in Germany, failed due to very strong opposition by NGOs and the Green Party.
    A general labelling could make people aware that GMOs have for long occupied everyday life and people do not want to give it up in medication, washing powder, T-shirts etc.

  2. Bonjour,

    First of all I would like to post in this topic and I apologize for my bad English and if this is not the right place.
    Mr. Andrew Kniss thank you for your always relevant articles.
    I wanted to share this work by scientific INRA (activists ?) (France) concerning the use of plant protection products in the USA.
    Also, I would like if possible to have your opinion. This work priori seems to be very focused on the substance and fits perfectly to the French anti-phobic atmosphere pesticides and anti conventional agriculture of the moment.

    Newspaper article(français).http://www.lemonde.fr/planete/article/2016/03/19/et-si-les-pesticides-coutaient-plus-qu-ils-ne-rapportent_4886135_3244.html

    The work of scientists from INRA (English).

    Best regards

  3. Great article, as a weed scientist and crop researcher i often ask gmo labelling proponents why they are singling out gmo for labelling, but ignore the hundreds of herbicides and insecticides that are used on the crop that are not related to the transgenic component? I have yet to recieve a credible response. All went through the same regulatory process. I have come to the conclusion that anti gmo really means anti big business!

  4. Thanks Andrew for the thoughtful and relevant comments about the GMO saga. I agree that the topic is getting a bit tiresome, but your graph about the prevalence of herbicide use is an important point. And you didn’t you didn’t delve into the old herbicide products that have been phased out; another important point.

  5. Consumers are primarily concerned with a perceived health risk of consuming a transgenic sequence in a GM-based product. The consumer movement for GM labeling on food products is not premised on level of herbicide residues on the food. The concern about glyphosate residues is a relatively recent entree to the labeling discussion. BTW, organic foods have lower pesticide levels than conventional foods, though ubiquitous presence of chemicals in our environment results in low levels being detected even on crops to which no herbicides have ever been applied.

    1. Care to share your sources for the “level of pesticides IN organic vs. conventional foods”?

    2. Yeah, Jane, I agree with Kyle. You’re going to have to show some proof here that there is a lower pesticide load on organic products at the level of commerce. From what i’ve seen, studies showing this conveniently ignore the plethora of pesticides approved for use on organic crops and report only on glyphosate.

      As for your last statement: ‘ubiquitous presence of chemicals in our environment results in low levels being detected even on crops to which no herbicides have ever been applied’ I agree, generally. I know that derivative residues of DDT can still be found in the environment in all sorts of places. This is more due to the incredible sensitivity of our technical equipment which can detect chemical signatures sometimes at the part-per-trillion level.

      Will keep an eye out for your citations!

    3. “BTW, organic foods have lower pesticide levels than conventional foods, . . .”

      How do we know that? What you are actually saying is that monitoring programs, such as the USDA’s annual pesticide residue sampling program, tend to find less residues of the pesticides the sampling program looks for on organic produce and other food products. And these pesticides looked for are the synthetic products commonly used in conventional agriculture, only a small portion of which can be used in organic production. So, it is not surprising that organic would have less detections of these.

      But, USDA does not currently monitor for pesticides more typically used in organic. Pesticides that are not excluded for purposes of meeting organic certification are still pesticides, with identifiable chemical composition, and in some cases, are more concerning for human health than the synthetic counterparts used in conventional ag. So essentially, we have a situation similar to only putting referees on the field to look for infractions committed by team conventional ag. So not surprising that we find, continuing the analogy, at the end of the day team conventional was found to have committed five holding infractions, a few offsides, illegal motion, etc, and team organic none. We don’t know if that is because team organic committed no infractions or if its just that the referees were not instructed to look for infractions committed by team organic.

      I actually do concede that you are likely to find fewer residues on organic, even if USDA started monitoring for the pesticide products organic growers use. I will also concede that the organic philosophy is one of minimizing resorting to chemical solutions. But even so, the levels of residues detected in USDA’s monitoring program actually instill confidence rather than alarm, that our regulatory programs for pesticide use are successful in keeping residues well below even very conservative estimates of what would constitute a health risk. So yes, pesticide residues in organic are typically lower, but the difference lack meaning. Its a lot like saying Joe and Peter both want to buy an item that costs $10. Joe has a penny and Peter has 2 cents. Is it meaningful to suggest that Peter is far closer than Joe to being able to afford the $10 item because he has twice as much money?

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