Natural Pesticides

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Robert Pavlis

In a previous post, What does Organic Mean, I provided some definitions of  the term Organic. Most people think of Organic food as being pesticide free. The lack of pesticides is one of the main reasons for paying higher prices.

People also think Organic food tastes better and is higher in nutrition, but both of these claims have been completely disproved. Today I’d like to discuss the issue of lower pesticide levels in organic foods.

natural Pesticides ingested daily
Natural pesticides ingested daily

Synthetic and Natural Pesticides

Traditional farming uses man-made (synthetic) pesticides and these pesticides do form residues on fruits and vegetables. When you eat an apple you do eat some of these pesticides. If you have read Chemicals in Coffee you will understand that the fact that the apple has pesticides on it is not the only important fact. You also need to know how much of the pesticide you eat. We’ll look at some numbers today.

What is the difference between ‘synthetic’ pesticides and ‘natural’ pesticides? Either type of pesticide can be safe or harmful to life. Synthetics are no more harmful than natural–natural does not mean safe. In fact I would prefer the synthetic ones since we test these and understand them. Most natural pesticides have not even been discovered yet – we don’t know how dangerous they might be.

Plant Science for Gardeners by Robert Pavlis

Natural Pesticides We Consume

The following data comes from Bruce Ames, (ref 1). It is very worth while reading.

In North America we ingest 0.09 mg of synthetic pesticides each day, mostly from the food we eat. That is a relatively small amount, but most people still get very concerned about this problem. In fact it is the reason for the whole organic movement – to eliminate synthetic pesticides from our food.

What about natural pesticides? It turns out we eat 1,500 mg of natural pesticides every day. That is 10,000 times more than the amount of synthetic pesticides. Some of these come from the natural pesticides sprayed onto organic food, but most of them are natural chemicals produced by the plants.

YouTube video

Plants Produce Natural Pesticides

Plants produce many chemicals to defend themselves against insects and other pests. There are thousands of these chemicals in every plant and each time we eat any part of a plant, we ingest these pesticides. On average we eat between 5,000 and 10,000 different natural pesticides, most of which have not been adequately studied by science. We don’t know how dangerous they are. What we do know is that humans have been eating them for generations without significant problems. We don’t need to get alarmed about these numbers.

Unfounded Fears of Synthetic Pesticides

Cooking our food produces 2,000 mg of burnt material, per day, per person (ref 1). This material contains many carcinogens and mutagens. Cooking food is a much bigger problem than synthetic pesticides!

A single cup of coffee contains the same amount of natural carcinogens as a years worth of synthetic pesticides from fruits and vegetables (ref 1). Restated a different way; eliminating a years worth of synthetic pesticides from food is like skipping one cup of coffee. You are far better off buying non-organic food and drinking less coffee – both would save you money.

The organic movement is good for other reasons that we will discuss in future blogs. I am not against organic practices in the garden. However, the main aim of this movement, to eliminate the synthetic pesticides, will at best account for a 0.01% reduction in the pesticides we ingest. 99.99% of the pesticides we ingest are natural and organic farming practices will not reduce these. In fact they just might increase them since plants now have to fend for themselves, producing higher quantities of their own natural pesticides.

Keep in mind that  we are still talking about small quantities of chemicals. Humans are very able to handle these in our diet (ref 1).

Chemicals are part of our lives and with few exceptions they are safe in small quantities. We need to learn to accept this fact.

To better understand chemicals you light also enjoy Fear of Chemicals.


1) Natural pesticides consumed on a daily basis:

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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

15 thoughts on “Natural Pesticides”

  1. What about farm workers. They are exposed to much higher doses of Ag applied pesticides. So the concept of dose related significance of synthetic input residues on consumer food seems mostly accurate but for workers in the field exposure can be many times higher. i have seen some pretty significant health issues from Ag exposure.

    • Total exposure is borderline irrelevant. What matters, first and foremost, is the chemical we’re talking about.

      Sure, even water will kill a person if the exposure level is too high. That’s nice. It has very little to do with the meat of this subject, which is “How toxic are these pesticides, both to humans and the ecology?”

      If a chemical is extremely safe in typical exposure ranges then it’s not, obviously, in the same discussion as something like dimethyl mercury — which killed a chemist when a drop or two went through a glove.

      Recency is another big problem with this comparison. A very large number of natural pesticides have been taken out of the human diet through thousands of years of human testing. By contrast, when you have an estimated 5,000 “trade secret” synthetic chemicals in the USA the situation is extremely different.

      Then, there are the sub-lethal effects, including chronic exposure. There is also the matter of synergistic effects. That is the only area where natural pesticides seem to be possibly relevant. If, for example, a person is exposed to the cyanide from “bitter” cassava (a natural pesticide) then exposure to various synthetic pesticides might be even worse for that person due to his/her weakened state.

      The guy who recommends eating garlic mustard on his “eat the weeds” site is reckless, in my opinion. I have eaten that plant and it made me sick. I am sensitive to cyanide compounds in plants and can’t even tolerate processed tapioca. Yes, natural pesticides can be toxic, sometimes extremely so (Aconitum for example). So what? No one is planting acres of Aconitum as a food crop. They have had thousands of years to figure out that that’s not a good idea. People also have methods to reduce the cyanide in bitter cassava.

      What people don’t have traditional methods for are trade secret synthetics and “inert” strongly-toxic chemicals slipped into pesticide formulations, their toxicity masked by exposure calculations that only use the “active” ingredient.

  2. Relying on a single source for scientific data is a slippery slope. Assuming our bodies can handle small amount of potentially poisonous chemicals is also. Many of these are potentially dangerous at levels as low as a few parts per million. Making a generalization inferring that pesticides are safe without knowing how much is in or on our food is like saying Russian roulette is safe with just one bullet….

    • Not sure where you are getting your conclusions. Where did I say “pesticides are safe” or that “our bodies can handle small amount of potentially poisonous chemicals”?
      I think you missed the point of the post. And that is people fear synthetic, when they actually eat relatively huge amounts of natural pesticides and don’t fear them at all.

      • That’s because people have, through trial and error, figured out which natural pesticides shouldn’t be consumed and/or how to remove them through processing.

        Cassava poisons people due to its natural pesticides and yet its toxic (“bitter”) form is the one that’s most farmed. The “sweet” type is not toxic but the “bitter” pesticides the plant produces makes life easier for farmers.

        Another example is quinoa. A form was bred that doesn’t have the soap-like chemicals on the outside of the seeds that cause stomach pain but it isn’t farmed because birds are much more likely to eat the seeds prior to harvest.

        People don’t grow Aconitum in their gardens as a food plant. They realized, long ago, that it’s unsafe to consume its natural pesticides.

        I think your argument is deceptive. The number of natural pesticides is a trivia piece and so is the total amount, as long as the total amount is a safe amount. It doesn’t matter if people were to consume 10 million of them if they’re not as harmful as one or two synthetic pesticides. What would actually matter is the toxicity of those synthetics.

        Humanity has had thousands of years to test a lot of the natural pesticides, like Aconitum’s. Many synthetic chemicals are very new to us. A huge number of chemicals are even labeled “trade secrets” and there is an “inert” loophole that’s used to put higher-toxicity chemicals into formulations for glyphosate and such — using the glyphosate instead to determine exposure limits.

        The industry is full of tricks because of its pursuit of profit over ecological soundness and human health. POEA has been tested by researchers on human cells and they found it to be 3,000 times more toxic than glyphosate, the supposed active ingredient in “glyphosate” products. Neonics, from what I’ve read, are perhaps the most dangerous to pollinators due to sub-lethal effects (like making them easier prey for the Varroa mite, making it harder for them to forage, etc.).

        • Re: “That’s because people have, through trial and error, figured out which natural pesticides shouldn’t be consumed and/or how to remove them through processing.”

          You missed the whole point of the article. You eat these natural pesticides every day as you eat fruits and vegetables.

  3. Hi, Robert.

    “A single cup of coffee contains the same amount of natural carcinogens as a years worth of synthetic pesticides from fruits and vegetables. ”

    You’ve made a leap from ‘natural pesticides’ to ‘natural carcinogens’ there. Which synthetic pesticides are you talking about specifically? Which natural carcinogens are you talking about specifically?

    Can you back that up, because without specific references, it seems like you are piling several assumptions on top of each other to reach a conclusion.


  4. Are you assuming that natural pesticides are unhealthy? If so then shouldn’t we be avoiding plant foods altogether? And do you think that honeybees are dying on a large scale because of natural pesticides? And do you think pests are mutating into super pests because of natural pesticides?

    • I did not assume natural pesticides are unhealthy, but many of them probably are. But a natural pesticide that tastes bad to bugs, may not cause us any harm.

      The important point of the post is that chemicals are only harmful if they are present in large enough concentrations. Our bodies are designed to deal with low levels of all kinds of nasty chemicals. It is only when doses get high, that our bodies can’t handle them. There are lots of things in fruits and vegetables that would kill us at higher doses.

      Honeybees tend not to eat the leafy parts of a plant. They eat the nectar and pollen which are produced to attract insects. Plants would not survive very long if nectar and pollen killed the insects that are needed to pollinate their flowers.

      I am sure that pests adopt to natural pesticides. I would not call them supper pests. A common example is the monarch butterfly. It can eat the milkweed plant which produces a natural pesticide that kills most other larvae. But genetic mutations have changed the internal chemistry of the monarch so that it is not affected.

  5. An excellent idea to put together this site Robert – I learned of it from the MG list-serve. (if that’s what it is still called)
    My blog began as a gardening site and has taken a whole different route since I started it. I’ll enjoy reading what you have to share.
    Judith, emerita

  6. I am curious about this statement “However, the main aim of this movement, to elliminate (sic) the synthetic pesticides, will at best account for a 0.001% reduction in the pesticides we ingest. 99.99% of the pesticides we ingest are natural and organic farming practices will not reduce these.” Can you please provide a reference to support this assertion?

    • The reference for the numbers is given above. Since 99.99% of the pesticides we consume are natural – going Organic will not reduce this amount. Elliminating the synthetic pesticides can at best elliminate the 0.01% that is synthetic.


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