Steve Savage

The Lowdown on Pesticides with a Plant Pathologist

As I delve further into the depths of agriculture, particularly in respect to GMOs which has become my pet project, I am consistently astounded by how much I don’t know. Granted, that hasn’t stopped me from forming, having, and propagating opinions, but always, in the recesses of my mind, preparing myself for the possibility that what I take for granted and believe in may be wrong.

I was once wrong about GMOs, and then I was wrong again on pesticides. Continuing on in the same vein as my Lowdown on GMOs series, I’ve reached out to plant pathologist Steve Savage to pick his brain on pesticides as it is perhaps just as big an issue as the use of GMOs today. Enjoy.


0 – Lots of folks are increasingly having concerns over pesticides. In that regard, before we begin, I think it will pay dividends to define a few things

i – Could you give a brief bio of yourself, your experiences, competencies, and why people should trust your judgment?

I’ve been involved in agriculture for more than 35 years.  I got interested in a field called Plant Pathology steve savagewhen I was an undergraduate in biology at Stanford.  I ended up working in the lab at UC Davis that studied diseases of grapes and that was my first experience with farmers or with pesticides.  At the time there were several new fungicides that we were testing that were much safer for us and for the environment. That is where I began to understand that things were rapidly changing from the “bad old days” of pesticides.

When I finished my PhD, I worked briefly for Colorado State University with the grape and fruit industry in far western Colorado.  Again, I worked on many things, but also on some new chemical options for grape disease control.  I then spent seven years working in fungicide discovery at DuPont in Delaware and learned how much effort goes into looking for and evaluating new pesticide products.  My one frustration there was that I didn’t feel that our industry was doing a very good job of telling our story. Then I got the chance to return to California to work for Mycogen – a start-up that was focused on biological control of pests and on natural product-based pesticide options.  In the seven years I worked there we did some very interesting work, but it became clear that there were many pests, which we would never be able to effectively control with our “soft” products.  Since 1996 I have been an independent consultant doing projects for a wide range of ag-related companies.  I have probably worked equal amounts of time on projects related to synthetic pesticides, biological pesticides and crop genetics.  I’ve also spent a good deal of time on questions of sustainability – how to measure it, and what sorts of farming practices are most suitable for pursuing that goal.  For the last 5 years I’ve also been blogging and speaking on ag issues in general.

ii What is a pesticide, what do they do, what types of pesticides exist, and why do we need them?

There are lots of organisms that eat, infect, or otherwise damage plants. This is true for plants in natural settings and for plants grown as crops.  These include insects, mites, nematodes, fungi, bacteria, and viruses.  Plants also compete with one another for light, water and nutrients and in an agricultural setting we call those weeds.  In agricultural production, we call these pests, and they are managed by a range of practices, one of which is the use of pesticides. In terms of the pesticides used by farmers there are insecticides, miticides, nematicides, herbicides, fungicides and bacteriacides.  The reason that we need these materials is that without them the quantity, quality and/or safety of the crop can be compromised.  If a farmer tolerates say a 30% loss to pest damage, than means his/her use of other resources is only 70% of what it could have been – resources such as land, water, fertilizer, fuel, labor…  A pest-damaged crop might decay during storage or on the way to the consumer.  A pest-damaged crop might be colonized by fungi which produce seriously toxic mycotoxins.  There are also invasive pests like weeds and insects that can damage sensitive natural environments if not controlled.

iii Does it make any sense to refer to pesticides with a catch-all phrase? To give an analogy, the word cancer is quite misleading as there are 200 types of cancers. Yet the elasticity of the word has allowed conspiracy theorists to claim, with relative ease, that there is a cure for cancer that is being suppressed. If that were true, there would need to be 200 different cures. Does not the same situation apply to pesticides: that it damages their perception by squeezing them into one-size fits all category that can then be strawman’ed, mischaracterized, and misdefined? In short, is the elasticity of the word a detriment to public perception?

No.  Pesticides encompass a huge range of things.  Plants are actually the biggest producer of pesticides as most of them make defensive and/or repellent chemicals whose purpose is to ward-off pests.  These can be chemicals that are seriously toxic to mammals (e.g. nicotine or rotenone) or relatively non-toxic (e.g. azidirachtin, from neem trees). Sometimes we humans take a liking to the chemicals plants have made to defend themselves (e.g. caffeine in coffee or capsaicin in hot peppers).  Sometimes we have to be careful of the pesticides made by our foods – e.g. you shouldn’t eat the sprouts that can develop from potatoes in your pantry because they have some glyco-alkyloids that are rather toxic.  Some pests have evolved to get around those defenses and those are the ones that cause the problems in farming.

Technically the definition of a “pesticide” is legal – not chemical.  If any product is sold using “pesticidal claims,” then it must be regulated by the EPA as a pesticide.  Thus pesticides differ dramatically from one another.  Most modern pesticides are selective meaning that they basically only effect the target organism – e.g. only insects, or only diseases, or only weeds.  In most of these cases, the chemicals are inhibitors of specific enzymes in pathways that are not found in the non-target species. Some have “non-target” toxicity to things like fish or aquatic invertebrates, and those have to be used very carefully around water.  Others are extremely safe in those settings. Pesticides also differ dramatically in terms of toxicity to mammals (rats and mice are used to measure this as surrogates for humans – more about that later).   Some pesticides are things like plant extracts or chemicals produced through fermentation of things like bacteria or fungi.  Some pesticides are live biological organisms. Some pesticides are synthetic compounds and some are synthetic versions of naturally occurring chemicals.  Some (mostly old) pesticides are inorganic compounds like copper sulfate.  Many synthetic pesticides are structural variations of naturally occurring chemicals, which acted as the starting idea for a family of compounds with a similar mode of action.

1 – How are pesticides regulated? Is there, for example, any industry say-so in the standards; who performs the tests, analysis and what are the penalties for failing safety regulations?

Pesticides are highly regulated.  The main changes in that regard started with the establishment of the EPA in 1970, but there have been several iterations of increasingly stringent standards since then.  As with pharmaceuticals, the company that wishes to register a chemical, or keep it registered during a later review, must pay for the cost of safety testing.  Those tests have to be conducted under rigorous rules and the data and process are subject to government audit.  Many of these tests are conducted by contract labs, which would risk losing all their business if they were found to have falsified any data.  There are many categories of tests required which are nicely described in this post.  In general there are several categories of acute and chronic mammalian toxicity, tests for effects on various non-target organisms, and requirements to fully document the environmental fate and rates of breakdown of the chemical and its metabolites.  It costs a company over 200 million dollars to develop a new chemical, and a substantial part of that cost is for toxicity and other safety testing.  The EPA conducts an elaborate risk assessment based on this data and uses that to set very specific limitations on how the product can be used (maximum rates, protective equipment required, interval before workers can re-enter the field, time required before the treated field can be harvested…).  The labels are designed to ensure that any chemical residues on the harvested crop are below a very conservative “tolerance” that the EPA sets based on the risk analysis. Those that use pesticides professionally must be licensed to do so and must keep up with additional training.  There are substantial penalties if, for instance, a batch of a product does not been the standards for purity that have been set to determine what material was used for testing.  Companies are not allowed to make claims about the relative safety of their products, even when such differences occur.  The federal government and some states conduct pesticide residue monitoring on random samples from the food supply.  The farms from which samples are found with above-tolerance detections or detections of pesticides not registered for that crop are liable for those issues.

2 – Diving into toxicology

i How well do the tests, such as the LD50 performed on rats (readers: the LD50 is the lethal dose of a pesticide required to kill 50% of a group of rats), translate to humans?

Tests for toxicity have not been allowed using human subjects for some time; however, several decades ago some chemicals were tested on volunteers.  In general, higher levels of exposure are allowed for those compounds with human data because the safety margins applied to those with only rodent data are quite large. The EPA also factors in the toxicity of metabolites. Every year the USDA (and Canada and several states) conduct extensive sampling from commercial food channels and test for residues of pesticides or their metabolites (typically of >300 compounds per commodity, >10,000 total samples so more than 2 million rows of data).  Year after year, almost all the residues found are below the tolerance (e.g. 99.5% of the 2012 samples) and many far below.

ii And, if you could enumerate a few examples, how much produce would an ordinary person need to ingest to exhibit symptoms of pesticide poisoning?

One would have typically have to eat hundreds to tens of thousands of times their body weight to get a toxic dose (a calculator can be found here).  For fresh tomatoes in 2008, I calculated that for 99.8% of the samples one would have to eat over 100 times one’s body weight and for 73% it would have to be over 10,000 times your body weight.  I calculated that for the most potent residue detected on any strawberry in 2008, someone would have to consume 18 times their body weight over a very short time and all from that particular sample. For reference, with caffeine in strong coffee, it would only require consuming 0.6 times your body weight to get to a toxic dose.

There are websites where you can look at how the detected residues compare to tolerances (e.g. CropAudit).  Incidentally, residues are often detected on organic crop samples as well.  More than 40% of organic samples had detectable residues in this recent Canadian study.  Some of the residues detected in Canada were consistent with intentional use of the synthetic pesticide on the organic crop.  Also the typical testing only looks for synthetic pesticides and would not detect something like the use of copper fungicides on organic.

3 – There is a set of standards (“Certified Organic”) that differentiates pesticides from those more commonly applied. Could you explain the difference between the two groups of pesticides: conventional and organic. Is, for example, one safer than the other in relation to human health?

The criterion for what can be used as a pesticide on organic is that the material is considered “natural” by the committee that advises the USDA on this issue (NOSB).  Being natural does not in any way guarantee low toxicity.  Many of the most toxic substances known (e.g. alflatoxin, botulinatoxin, nicotine) are natural.  Organic pesticides have to go through the EPA as well.  If compounds are naturally occurring and found in common foods, the most expensive chronic tests are not required.  For instance a new potato spout inhibitor has just been registered through that path, but it is made synthetically because it would not be practical to get it from natural sources.  Typically, it could not then be considered ok for organic.  Organic growers use clove oil for sprout inhibition, but it has to be re-applied many times while this new material does not.  Some of the products that can be used on organic, like copper-based fungicides, are more toxic than many synthetic alternatives which are also more effective and used at much lower rates.  The bottom line; however, is that because all of these things are well-regulated, there are not any reasons for consumers to hesitate to eat either conventional or organic food, at least as long as it is produced in places like the US, Canada or Central or South America.  Some organic non-perishable ingredients are being sourced from places like China and India, and between general environmental pollution issues and the continued use of old pesticides, this is not a desirable thing.

4 – Many people still reference Rachel Carson’s Silent Spring published from 1962 in their deliberations against pesticide use, but have pesticides changed since then?

Dramatically.  I think that if Carson could come back and see the changes she would take great satisfaction.  She might well be annoyed about the people who are effectively implying that her efforts failed to produce a positive legacy.

i If so: for the better or worse?

I would refer you to a recent post in which I use the historical data for one crop to document the change over time (an example of how much pesticides have changed).  More and more of the pesticides which are being used fall into the EPA’s “category IV” which is called “essentially non-toxic.”

ii Many activist organisations point to the increased use of glyphosate (Roundup) usage since the introduction of GMOs. Is this true? If so, what does it mean for the environment? Has glyphosate replaced other pesticides products, or is it new product being applied increasing overall use? 

Glyphosate was probably already the biggest single pesticide product even before biotech crops.  This is because it is particularly effective as a herbicide, but has very low toxicity to everything else, does not move into water, and leaves treated sites available for immediate planting.  When glyphosate tolerant crops were introduced, glyphosate did replace other herbicides that had been in common use on soy etc.  It also replaced mechanical tillage in some cases, so that increase in pesticide use is a substantial positive for the environment because of reduced erosion and retention of soil carbon.  There is a widely cited study by Chuck Benbrook of the Organic Center which came up with a large estimate for increased use of glyphosate for biotech.  That work has been criticized for various assumptions and extrapolations that are disputable.  Others have calculated the opposite trend.  However, even if Benbrook’s numbers were accurate, what few point out is that it is a number for a total of 1.4 billion acres grown over a long time frame.  The amount comes to 6 ounces/farmed acre which is not at all dramatic. In his study, Benbrook also acknowledged that: “In light of its generally favorable environmental and toxicological properties, especially compared to some of the herbicides displaced by glyphosate, the dramatic increase in glyphosate use has likely not markedly increased human health risks.”

5 – From an environmental perspective, would we be better off with conventional pesticides, organic pesticides, both, or none at all?

We would be best off with whatever kind of pesticide option is both effective for pest control and has minimal environmental impact.  Sometimes that will mean a product that can be used in both organic and conventional (e.g. Spinosad – a very effective natural product insecticide produced by Dow that can be used in both).  Sometimes, the best environmental choice would be a synthetic.  To not control pests to a reasonable degree is problematic for the environment.  If say 20 or 30% of the potential production is not being achieved because of pest damage, that means that the use of all the other resources for that crop (land, water, energy, fertilizer, labor…) are only being used at 70 to 80% of their potential efficiency.  Farming more land to meet global demand is the worst possible alternative from an environmental point of view.  That is why it is a good thing for the environment that organic remains a small niche – otherwise a great deal of new farmland would be needed.

6 – How does international law affect national regulations? The EU and the US differ in their approach to pesticides, yet a significant amount of cross-food trade occurs. Are you aware of any effects this has in regard to the individual policies that the FDA, EPA, and DoA use and vice-versa for their European counterpoints? 

Different parts of the world have different specific regulations, but those mostly affect trade with regard to the maximum residue levels (MRLs) that are allowed by the importing country.  Some European MRLs are lower than in the US, but not all.  Pesticide use in Europe is actually quite high – particularly for fungicides because of the wetter climate.  If the EU were to shift to regulation based on hazard rather than risk (something they consider from time to time), it could become much more problematic for US and other North and South American exporters.  Europe is a major net importer of food and feed.  In the US, our regulatory agencies have consistently used risk-based regulation.

7 – Are you able to shed some light on the future direction that pesticides and pesticide usage might evolve?

In general I believe that the trend will continue towards more and more selective pesticides with lower mammalian and other non-target toxicities.  Herbicide use will become more diversified particularly in areas once dominated by glyphosate tolerant crops.  The use of Biological controls will continue to expand slowly, and will fill some important niches.  The lower cost option for the registration of certain naturally occurring chemicals will help with finding products for niche uses like the sprout inhibition described above.  The overall need for pesticides will continue; however, and may well intensify in some regions because of climate change.  Hopefully, pesticide regulation in the developing world will catch up and eliminate the known bad-actor materials that are still used all too often in those settings.  Plant genetic engineering could be used to dramatically reduce the need for certain pesticides on some crops (particularly coffee, grapes, potatoes, tomatoes, brindal…), but between activist influence in poor countries and brand protectionism in the rich world, those potential benefits will probably never be realized.

Thank you Steve, it was a pleasure picking your brain.


I’m sure you’ve had a few misconceptions shattered. If you enjoyed that, be sure to check out Steve’s blog, Applied Mythology, where, always coolly and calmly, he tackles the biggest issues of the day in agriculture in his friendly voice, and with evidence and science to back up his claims. As always, where one gets their information is very important. I hope you’ve learned something new today, most especially that pesticide fears are overblown. Please share this post if you value the opinion of experts above unsubstantiated banter; we can all learn to deal with a little humility.

What if much that you think you know about agriculture, farming and food isn’t actually true? What if there are “myths” that have been intentionally and mostly unintentionally spread about these issues? What if the truth about these issues matters for the future of humanity? ~ Steve Savage

Featured Image sourced from EPA. Profile of Steve sourced from his Google+

16 thoughts on “The Lowdown on Pesticides with a Plant Pathologist”

  1. Very good article, but one that sadly will fall on deaf ears. The last line in the interview is particularly important…..”Plant genetic engineering could be used to dramatically reduce the need for certain pesticides on some crops (particularly coffee, grapes, potatoes, tomatoes, brindal…), but between activist influence in poor countries and brand protectionism in the rich world, those potential benefits will probably never be realized.”…. this is what needs following up. Activist influence and brand protectionism will do more environmental damage than glyphosate ever will.
    David

    1. Thank you. I share your concern in regard to that last line. So much we can do to lessen the sky-high environmental foot print of agriculture, but those who claim they are helping the environment will block them. George Orwell’s double-speak in action!

  2. Great interview Fourat, and a great read. Admittedly I haven’t done much research on the subject, but am a bit of a skeptic when it comes to the purported benefits of organic produce vs. conventional (mainly because I hate spending twice as much on groceries). Of greatest importance to me is how far the produce has traveled before I pick it up at the store, and how fresh it is, but not everyone has the benefit of living around a large concentration of family-owned farms.

  3. It’s refreshing to read something about pesticides and pesticide use that’s written in a calm, scientific and non-inflammatory tone. Rational discussion on topics like this is rare. It would be good if this post could be put into a shorter and simplified version suitable for mass distribution in publications such as, say, Readers Digest, where those of a less technical bent could be exposed to it.

  4. Great read Foo, as an employee of Dow I have been able to see and read about all the things that Dow as a company is doing to improve the food that the world consumes. Also living out in the rural areas of Texas I constantly see the farmers working their land and the pesticides being applied to the crops. It makes sense to me that it is needed to a certain point to control what would otherwise be a destroyed crop. I think that to some point the foods themselves are altered in some sense that it is resistant to the fungus, bacteria and pest without the need of chemicals.

    1. Cheers Kev. Those foods you mentioned as having been altered are GMOs, and yes, as you say, they curtail the amount of pesticides and other chemicals used, among other beneficial factors. Glad you liked the read 🙂

  5. Great interview. I think the point Steve makes about organic remaining a small niche is important. So many people consider the decisions they make in the supermarket to impact only their family, without realizing that they actually influence the whole industry. For the sake of the rising population, I also hope it remains a small niche.

    1. sew21d,
      2 things will keep it a niche. The philosophically-driven limitation to “natural” will limit the productivity and enhance the risk to the point where even the “premium” does not motivate a great many farmers to go organic. The rest of the system from processors through retailers do quite will on their own mark-ups on organic, but only as long as it is a premium priced niche. Even when Organic was growing “rapidly” leading up to the recession, it was only on track to something less than 3% of UC cropland by 2050. (Steve Savage)

  6. Reblogged this on Socio-Economics, Biosafety & Decision Making and commented:
    Understanding the role that pesticides have in terms of benefits, costs and risks is important to help us make better decisions as a society. Steve Savage (author blog Applied Mythology) does this brilliantly in helping us demystify and demythologize pesticides. Interview was done by Fourat Janabi (author blog Random Rationality) another excellent blog covering science and its role in society. Highly recommended both blogs.

    1. Thanks jflack and fourat for getting this out there. Coincidence, today Applied Mythology just crossed the 1/4million historical page view mark

      Steve

  7. […]  In the 20th century, several things changed. The World’s population grew exponentially (as is its habit). More food was needed to feed everyone. The World Wars occurred. Many scientific efforts were directed to the creation and dispersal of weaponized chemical agents. This research eventually led to the making of synthetic pesticides. […]

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