Glyphosate use in wheat

A blog post titled “The Real Reason Wheat is Toxic” has been making the rounds on social media. The post by the “healthy home economist” is riddled with errors and misinformation.The post contends that glyphosate is commonly sprayed on wheat at harvest time, and that glyphosate then causes health problems when the wheat is consumed. Shortly after it started circulating, two excellent rebuttals were posted online, one by Sarah Schultz, and another by Jenny Dewey Rohrich. Both Sarah and Jenny do a great job pointing out that spraying glyphosate onto wheat at harvest time is actually a pretty rare practice, done with great care when needed. Most glyphosate used at harvest time is done on spring and durum wheat, and mostly in the northern tier States (North Dakota & Montana) and some Canadian provinces. But about 75% of US wheat acres are winter wheat, and pre-harvest glyphosate application is very uncommon on winter wheat. If you’ve seen the original blog post, I would encourage you to read Jenny & Sarah’s well-researched responses.

The figure that the healthy home economist uses in her blog post was originally from a paper by Anthony Samsel & Stephanie Seneff, two people with no formal training in this area. Their paper claims that glyphosate is responsible for just about every disease imaginable. This particular figure shows the incidence of celiac disease diagnoses increasing as a rate proportional to glyphosate use in wheat. I think it is pretty well understood that just because two things are correlated, doesn’t mean there is any cause & effect relationship. The figure below really doesn’t mean anything other than two unrelated things increased at about the same time. GlyphosateSamsel

But there is one aspect that I haven’t seen explained elsewhere. Why has glyphosate use in winter wheat increased? I checked the NASS database used in the Samsel article back in February, and the glyphosate use data they show does seem to be reasonably accurate. Glyphosate (the active ingredient in Roundup herbicide) can’t be sprayed on the wheat while it is still green, because that would kill the wheat. This fact has lead many to believe that the pre-harvest application of glyphosate must be the reason for the increased use. But glyphosate use for winter wheat harvest is extremely rare. If this is true, how can we explain the increased use of glyphosate in winter wheat?

The answer is that the glyphosate shown in the Samsel figure is not actually being applied to the wheat at all. The glyphosate use data for wheat is actually an artifact of the way USDA-NASS estimates pesticide use. Pesticide use data is collected using a survey. The question asking about pesticide use asks respondents to include any pesticides applied since they harvested the last crop. For example, here is the question about pesticide use from the 2009 winter wheat survey (emphasis mine):

“Now I have some questions about all the biocontrols or pesticides used on this field for the 2009 winter wheat crop, including both custom applications and applications made by this operation. Were any herbicides, insecticides, fungicides or other chemicals used on this winter wheat field for the 2009 crop?  [Probe for applications made in the fall of 2008 (and those made earlier if this field was fallow).]


Winter wheat in much of the US Great Plains is grown in strips alternating with idle land (fallow). The next year, the fallow strips will be planted to wheat.

So the glyphosate shown in Samsel’s figure could have been applied any time after the last crop was harvested. A large percentage of US wheat is produced in the dry regions of the West. In these dry areas, one of the most common cropping practices is wheat/fallow rotation. There is simply not enough precipitation to produce a crop every year, so the fields are left idle every other year. So for many winter wheat fields in the UDSA survey, the pesticides could have been sprayed any time since the previous wheat crop was harvested; a period that spans up to 15 months in some regions.

In the wheat/fallow rotation, weed control during the fallow period is extremely important. If weeds use the water during the fallow period, it will not be available for the subsequent wheat crop and yields will suffer. Historically, tillage was used for weed control in the fallow period between wheat crops. But each time the soil is tilled, moisture is lost. In many rain-fed wheat production regions, reduced tillage systems have been adopted where wheat stubble is left on the field, and the weeds are controlled with herbicides instead of tillage. The most popular herbicide (by a wide margin) in these conservation tillage systems is glyphosate. And it just so happens that the increased use of glyphosate in wheat corresponds quite well with the percentage of wheat acres that had residue present after planting.

Glyphosate use in winter wheat, and the percentage of wheat acres that had residue present after planting.

Glyphosate use in winter wheat, and the percentage of wheat acres that had residue present after planting.


The percentage of wheat acres that had residue after planting is probably a pretty good estimate of fields that had no tillage since the previous crop was harvested, because any tillage would bury the previous crop residue. And if tillage was not used prior to wheat planting, it is highly probable that a herbicide was used to control weeds before planting. And glyphosate is probably the most popular herbicide choice in these situations.

Now, it is important again to recognize that this correlation does not necessarily mean causation; it is possible that the adoption of reduced tillage systems is not causing the increased use of glyphosate. But since pre-harvest glyphosate application is rare, and spraying glyphosate to the growing crop would kill the crop, the increased glyphosate use in the last decade is almost certainly from applications made before the wheat was even planted. So the healthy home economist is going to have to look elsewhere to figure out “the real reason wheat is toxic.”

[Updated November 21 to clarify difference between winter, spring, and durum wheat.]


  1. Also it is worth noting that glyphosate is not really “toxic” at all. Very safe compound…. People are suckers for an embellished, exaggerated for effect story.

    1. Glyphosate certainly IS NOT SAFE. It is an industrial cleaner, used for descaling tanks, it is also an antimicrobial. it kills BENEFICIAL GUT BACTERIA. Thus allowing overgrowth of bad bacteria. Animals and humans, who digest this microbial/registered antibiotic called glyphosate, lose the ability to digest food ….. thus the rise in intestinal disorders. Anyone who uses this stuff, directly on an about to harvest food crop, should be on trial for damn poisoning the food.

    1. Yes mem, the GMO wheat was found when he sprayed his fallow field with glyphosate to kill off the volunteer plants before planting the next crop. This is an extremely common practice.

    2. Mem, are you OK? They are spraying non GMO wheat with an industrial CLEANER, 7 DAYS BEFORE HARVEST. You ok with that? Or are you going to say, ah we wash all the wheat, and all the absorbed industrial cleaner in the wheat is all gone when we make bread? Havent you noticed how suddenly bread doesnt go mouldy anymore? I am not the only one on this planet to notice that, and if it doesnt go mouldy, we cant digest the stuff either.

      1. Most wheat is NOT sprayed with roundup just before harvest. Perhaps 1% is, and then at a growth stage when the seed is done growing and cannot absorb the chemical and is inside the husk which protects it. I have grow wheat (my only crop) for 40 years and I know what the common practice of growing is.
        I just used some baking soda to clean tractor batteries and cables and sometimes I use vinegar to clean with in my shop. OH MY!!!! Those are INDUSTIAL CLEANERS !!! I Better get them out of my kitchen!!!!! Thanks you

        1. Nah, your whatever, doesnt clean out industrial sized boilers, that needs a descaling agent, called glyphosate. Baking soda, haha, rofl, never heard of that used on an industrial scale to descale massive water tanks !! haha yyoumake me smile 🙂

          1. Could you please supply me with the trade name of the INDUSTIAL glyphosate used in descali g tanks and perhap the MDS info. What would the dose be and how is it applied? I have read comments like yours but have never found proof it is done.

        2. Also mem, if you use baking soda, and what vinegar, dont think that would taste nice sprayed on the wheat, before harvest, for my flour, do you?

  2. The Samsel and Seneff graphs imply – for the correlation = causation theory to have a beginning of plausibility – that the effect of glyphosate is immediate. This hypothesis, in turn, must be divided in two: firstly, the ingestion of glyphosate must immediately cause « hospital discharge diagnosis (any) of celiac disease » or even death due to intestinal infections (in this case, the two curves coincide even better); secondly, the wheat produced in a given year must be consumed in the same year.

    Their figure 3 purports to show « an association between glyphosate and thyroid disease [that] comes from plots over time of the usage of glyphosate in the U.S. on corn and soy time-aligned with plots of the incidence rate of thyroid cancer in the U.S. ». Again, there should be an immediate effect to support the fact that the two factors evolge simultaneously, without time lag. There should also be a reasonable explanation of how glyphosate in corn and soy would reach the American’s table. As far as I know, you are not faring on polenta or tortillas every day. And there should be an explanation as to why glyphosate spread on other crops would have no incidence (that it has no incidence is suggested by the fact that the two curves match almost perfectly).

  3. Hello.

    I am not going to comment on the literature review by Seneff et al, because it is a review of 286 distinct studies. The reason for my post is that all of your assumption based evidence does not substitute for a report on actual glyphosate residue levels in market wheat as well as other GMO crops, which needs to look somewhat like this study on soybeans- -which, by the way, contradicts the politically motivated concept of “substantial equivalence”. The technology to detect and quantify herbicide residues is readily available in any university or large city. Anything other than data on herbicide residues is just fancy guesswork.

    Glyphosate is most definitely toxic. It has estrogenic activity and has been shown to stimulate estrogen responsive breast cancer in cell culture in Parts per Trillion . In dismissing cell culture studies as ” studies in a Petri dish” you are denying the legitimacy of an entire field of stem cell research conducted in ….cell culture.

    Aside from that little tiny problem, glyphosate toxicity is potentiated 100 fold by its adjuvants. This has been reported by unrelated scientists using different models, and is true of most pesticides. Inactive proprietary ingredients are in fact very active, are not tested by regulators. Denying this body of non controversial research just makes you look like science deniers akin to the tobacco industry.

    Have a great weekend.

  4. There actually can be certain cases where wheat can be toxic but not from glyphosate. This year a lot wheat farmers in my area had problems with vomitoxins forming in the wheat do to cool damp weather. Because of the cool damp weather farmers had to let wheat sit out in the fields longer. If the levels of toxins are high enough it can cause people to get sick. Usually the grain elevator tests for this and if a load is found to be too high it will be rejected.

  5. Would have to agree with Sarah and Jenny. In SW Ontario we don’t have many wheat acres ( in Bothwell area ) maybe in the 10000ac range and less then 1 % of those acres were sprayed with a glyphosate preharvest burndown.
    The acres that were sprayed, were the acres that farmers tried to get away without spraying in the spring. Vomitoxins more of concern then glyph.

    1. Wheat is not sprayed pre harvest burndown, why would one waste glypho on the stubble about the be burnt? Burning kills the weeds. Wheat is sprayed 7-14 days pre harvest, to increase crop yield. Anyone who knows anything about horticulture, knows a dying plant attempts to put all the efforts into the fruit/seeds. It is a commercial practice, to INCREASE YIELD> . If none of you farmers know that, I wonder if you are indeed real damn farmers.

      1. 1. Burndown refers to killing weeds. As in dead weeds dry down and do not cause problems at harvest. Wheat stubble is not burned with fire after harvest. It is use as mulch to increase soil quality.
        2. Some weeds do servive fire, Rush Skelton weed, Canada thistle, morning glory and many more.
        3. The wheat plant forms the seed about 2 months before harvest, and at the time you claim it is sprayed “just before harvest” the seeds are mature and drying up so they can be harvested.
        4. Have you ever visited a farm and walked in a field of wheat?
        5. I have grown wheat for 40 years, please learn the truth, don’t insult those who grow you food!


    Preharvest is the best time for controlling Canada thistle, quackgrass, perennial sowthistle, dandelion, toadflax, and milkweed.
    A preharvest weed control application is an excellent management strategy to not only control perennial weeds, but to facilitate harvest management and get a head start on next year’s crop.
    This Preharvest Staging Guide provides information on how to maximize the efficacy and benefits of Roundup WeatherMAX® and Roundup Transorb® HC herbicides in a preharvest application. The Guide is designed to help you assess weed and crop staging, and maximize your herbicide investment.
    In addition to delivering the best products and technologies, we also endeavor to deliver the best information and service of any company in the field.
    It is with that philosophy that we produce this guide – to help you get the most out of our herbicides.
    If you have any questions about our products call Monsanto’s CustomCare® line at 1 (800) 667-4944.

    1. Faye, first your link is to the Canada’s label, US farmers follow this one . . Yes it does show how to spray pre-harvest wheat, that does it prove how much if any is sprayed. Please read section 9.4 “fallow systems” most roundup is used in Chen-fallow, aid to tillage and pre seeding.
      I have grown wheat for over 40 years & know how roundup is used, please read and ask questions.
      We grow healthy wheat. Thank you

    2. Yeah isnt that absurd, so spray a big huge crop of wheat, in which there are no weeds, they already all be smothered, instead of stating the real reason for spraying 7-14 days before harvest of a healthy crop, TO INCREASE YIELD. Pure greed, it seems spraying a crop with an industrial cleaner, pre harvest, or anytime for that matter, seems the right thing to do, as long as you sell the crop, BUT DONT EAT IT YOURSELF. Spraying any food crops, at any time with an industrial cleaner, antibiotic, is an absurd and horrific practice. Pretending glyphosate is some natural healthy substance, even more obscene.

      1. Spraying wheat 7-14 days before harvest does not increase yeild! Most of the plant is dead, including the seeds.

  7. Great reply, oh the lengths Monsanto will go to, and people they pay, to dismiss genuine science with ridiculous replies. my specific area of expertise is the fraud called DTap, and the facts that CDC, by trying to cover this fraud and useless vaccine, are now prevaccinating babies, before birth, with Dtap, that kills them if given at birth? USA now has more in utero baby deaths, from this vaccine, than even first day baby deaths (and that is the HIGHEST in the civilized world). And if the babies survive this toxic onlsaught while still in the womb? they are born with 1 in 50 chance of microcephaly. USA now has 25,000 cases of vaccine damaged microcephalic babies a year, more than brazil, and no mossies to blame in USA! So CDC please explain why you trying to blame vaccine damage on a mossie?

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