Gardening: Truly Non-Toxic Pest Control

The Problem with Common “Organic” Solutions

When new to gardening, you will undoubtedly face a slew of pests on your tender edibles. Aphids, spider mites, squash bugs, tomato horn worms, and more will likely take up residence in your lush new outdoor food factory. What a lot of gardeners do is freak out and try to save their plants using whatever the friendly folks at their nearest garden center tell them will work best. It took (literally) decades for my grandfather to give up chemical pesticides.

Of course, when our garden first fell victim to garden pests, I did what I always do when I have a problem and need an answer: I went to Google. Experienced folks who are happy to give advice in organic gardening point to alternatives to the most common pest poisons. These are often naturally occurring, derived from nature, or are said to have a lower environmental impact. These are listed by the USDA as meeting OMRI standards for Organic agriculture. For this reason, a lot of people tend to think that they are perfectly safe. (I give a little more information on this at the end of the article. )

Just like we stress in regards to nutrition and hygiene, I see no reason to relax on our normal standards of doing things here. It is important to do your own due diligence rather than trust the funded research and federally regulated labels. You can be sure that if the government is managing it, it is far from perfect. This is certainly the case in modern standards for the USDA Organic label. Below are some very common pesticides that are used (and too-often overused) in organic gardens, and why I can not in good conscience recommend using them after having researched how to handle our own garden pest problems.

Spinosad (from Saccharopolyspora spinosa)

This is derived by fermenting Saccharopolyspora spinosa bacteria. It is used as a contact insecticide, but it is equally effective if eaten by them. It is highly toxic to pollinators like bees (save the bees!), and is “slightly toxic” to humans.

Lower body weights and increased mortality occurred in rats given 0.4% spinosad. Microscopic effects were observed in the adrenal glands, liver, lymphoid cells, reproductive tissues, kidney, thyroid, stomach, lung, and skeletal muscle of rats given ≥ 0.05% spinosad, and consisted primarily of vacuolation of cells; however, degenerative, regenerative, and/or inflammatory changes were also noted in some tissues.

via—Oxford Journals-Toxicological Sciences: Spinosad Insecticide

It is popular in organic gardening circles, but I do not recommend it. Why? It is toxic to too many species. This is a newer entry into the organic insecticide market, and like others, I suspect that there will be more problems surfacing.

Sevin (carbaryl)

(note: this one is not technically considered organic, but it is often used as a last line of defense by many organic gardeners.)

Toxic to humans. EPA listed as a carcinogen. If that weren’t enough, it is not a targeted pesticide. It kills the beneficial insects, including honeybees. (no bees means no food. consider them before all household, garden, and landscape chemical applications..including cleaners)

A member of the n-methylcarbamate class of pesticides, carbaryl can cause cholinesterase inhibition in humans; that is, it can overstimulate the nervous system causing nausea, dizziness, confusion, and at high exposures, respiratory paralysis, and death. Carbaryl is a reversible inhibitor of acetylcholinesterase. — CARBARYL IRED FACTS (EPA Office of Pesticide Programs)(pdf)

While carbaryl is deemed as safer than other common chemical pesticides, it is neither non-toxic nor safe. We recommend avoiding it.

Bt (bacillus thuringiensis)

This is one that I find particularly interesting. It is a bacteria, which means it is naturally occurring. Naturally occurring means safe, right? The EPA deems it to be safe, which makes it much more popular among organic gardeners than carbaryl(Sevin). However, the influenza virus is naturally occurring, and we don’t go carelessly contacting those who are infected, do we? Let’s be smart about this. The first question is, “how does it work?”

  1. Insect eats Bt crystals and spores.
  2. The toxin binds to specific receptors in the gut and the insects stops eating.
  3. The crystals cause the gut wall to break down, allowing spores and normal gut bacteria to enter the body.
  4. The insect dies as spores and gut bacteria proliferate in the body.

source—University of California San Diego

It works by damaging the internal gut lining of the offending insect. Does this translate at all to human health? Well, yes and no. Tests have revealed that it persists in human gut flora as tested on rats, the only result we have to go on is that there was no “significant” effect on native gut flora. However, it did migrate to the spleen on its own. The test, as far as I could tell, did not last for more than 2-3 weeks.

In another test, it caused pneumonia in mice, and spread to other organs. Some have speculated that it is toxic to Monarch butterflies. While this has apparently been disproven, we do not know which strains of bt were tested in the tests that were performed to disprove the claim.

It is linked to food poisoning. As in, the presence of bacillus cereus(bacteria responsible for food poisoning) was owed to the presence of bacillus thuringiensis. (click for source)

Last but not least, it is strongly contributing to the natural development of pesticide resistance. While not all bad itself, it does lead to the use of stronger and higher volume of use of toxic pesticides. Many scientists also link the use of bt in genetically modified crops as a major contributor to colony collapse disorder. The fact that it’s cheap to produce means that it has a lot of loud voices advocating its safety, and very little in the way of legitimate research into the long-term affects of its use, and the broadcast communication of what research has been done. When in doubt, leave it out.

Pyrethrins (pyrethrin and synthesized pyrethroids such as permethryn)

This is most often used on clothing as a repellent, but it certainly has insecticidal properties. It is derived from the seed casing of the Crysanthemum ( crysanthemum cinerariifolium) flower. It is naturally occuring, and therefore biodegradable. It is deemed as safe to use around foodstuffs by the USDA. Too good to be true? Possibly.

It is a known neurotoxin. Warnings are included that it should be applied only to clothing (when used as personal repellent), contact with skin can cause irritation and pain, especially when exposed to direct sunlight. Not surprising, since it is, once again, a neurotoxin.

Inhaling high levels of pyrethrum may bring about asthmatic breathing, sneezing, nasal stuffiness, headache, nausea, incoordination, tremors, convulsions, facial flushing and swelling, and burning and itching sensations. The most severe poisonings have been reported in infants, who are not able to efficiently break down pyrethrum.

via—Extension Toxicology Network-Cornell University

Exposure has been shown to result in slowed mental/neural development. (again, it’s a neurotoxin) Why does it make the list of common solutions to avoid? It is toxic to the nervous system.  Avoid it if you can.

Dish Soap 

This is generally derived from petroleum (which carries with it a host of carcinogenic and environmental damaging properties), and usually includes Triclosan, an endocrine disruptor. (See Keeping Our Hands Clean: Is Your Soap Safe?)

What Works on Pests but Not on People or Pets

The purpose of growing a vegetable garden is to be able to eat and enjoy the fruits of your labor, to improve the nutrient contents and health benefits of your food, and maybe, if you’re like me, for a little personal therapy. Personally, I would find it hard to enjoy the bounties of nature knowing that I had done a small part in its destruction, and possibly the slow poisoning of myself, my family, or friends who have shared in the harvest. These are a few very effective ways to deal with garden pests that won’t leave you second guessing the happiness you feel when you taste the delicious complexity of that beautiful heirloom tomato fresh from the vine.

These are listed in order of personal preference.

Beneficial Insects


Like having a cat to get rid of mice, nothing is more effective on getting rid of pests like their natural predators. Fortunately, they often introduce themselves when their favorite foods are available, but you can also release them for the same effect. Lady bugs, lacewings, praying mantises, predatory flies, and wasps are all valuable assets to the garden. They help eliminate the pests that feast on your garden plants using the existing natural method, which means no harm to your plants, your health, or the environment. They are available at most big-box gardening centers, but we always recommend supporting your favorite locally owned nursery.

Beneficial Nematodes

Photo credit:

Nematodes are microscopic roundworms. A few species are used for targeted pest control.

90 percent of nematodes reside in the top 15 cm of soil. Nematodes do not decompose organic matter, but, instead, are parasitic and free-living organisms that feed on living material.


They are effective against a wide range of soil-dwelling pests. They stop many pests before they emerge, including the squash beetle, termites, japanese beetle, weevil, and more. Certain species are used for specific pests, so talk to your provider (or do your research) to find out what you need for your particular problem. They are harmless to animals, humans, and pollinators. This is really not much different than releasing beneficial insects (like ladybugs), except that these stay in your soil, and continue as long as there is sufficient moisture in the soil, and there are enough prey present. I have tried it, and they do work. However, they can be expensive, especially if you have a big lot. They are also recommended to be reapplied every 4-6 weeks.

What I like about it: natural, literally harmless to people, pets, and plants, targeted (it doesn’t kill beneficial insects), and easy to apply (hose end sprayer).

Neem Oil


Neem oil is derived from the neem tree. It is often used in cosmetics, such as toothpaste, mouthwash, and for use in various balms and ointments. It is easy to find, and if you buy a cosmetic or food grade version, it can be used for far more than pest control in the garden.

It must be consumed by the pest for it to work, and it does not continue in effect on predatory beneficial insects (like lady bugs). That is, an aphid that sucks a plant leaf will be affected by the neem oil, but the ladybug that eats the aphid will not be affected. How does it work exactly? Neem oil contains chemicals that behave like hormones in insects, and are taken up just like their native hormones. It messes with their little brain centers, and causes them to forget. To forget what? To forget to eat, forget to mate, forget to do things that are essential for their persistence in your garden.

Does it hurt bees? No. At least, not usually. If the bug doesn’t eat it, it isn’t affected. If it does, it dies. The best part? It doesn’t take very much. I mix 1 tablespoon of neem oil and 1 tablespoon of Dr. Bronner’s liquid castille soap (note: we do not recommend using a dish soap like Dawn®) with 1 gallon of water in a sprayer. (the sprayer I use is not used for chemicals. in fact, this is the strongest solution it has seen). I also use neem oil in our homemade toothpaste recipe, and Mrs. AJ uses it in an all purpose “fix anything” balm that works well as a naturally derived replacement for commercial first-aid antiseptic gels, and is also good for bug bites (chigger bites itch for three days whereas they used to itch for three weeks).

Bonus: it is also an effective treatment for powdery mildew.

IMPORTANT NOTE: That having been said, do not eat it. It can be toxic to children if consumed, which means you probably don’t want to consume it while pregnant or nursing, either. At the small dilution I use, and the fact that I use it with soap, I don’t worry too much. It could be much worse. MUCH worse. Read more if you’re interested:

Diatomaceous Earth


Diatomaceous earth is the fossilized remains of diatoms. It is almost pure silicon dioxide (~89%) with 28 trace minerals. It is important to only use Food Grade Diatomatceous Earth, as filter grade has been heat treated to create more crystalline silica, which can cause some serious damage if ingested or inhaled, and it is not biodegradable. The food grade version is pure, untreated, and contains no more than one half of 1% of crystalline silica. It is most often used as an anti-caking agent in food and animal feed (as well as a kind of preservative in the latter due to its anti-bug properties).

I do not recommend doing this, but some people take food grade DE internally as a supplement/cleanser (think activated charcoal in regards to its cleansing aspect). The good: it is completely harmless to humans, pets, and the environment. It works (I use it in our home for pest control), and is good for several uses. (some people use it in homemade toothpaste, deodorant, and probably other applications I’m not currently aware of)

The bad? Since it is a mechanical pesticide (not chemical), it is non-selective: which means everything that touches it is affected by it. For this reason, use in the garden should be done very carefully. AVOID BLOOMS unless you hate pollinators and the work that they do. (if that’s you, what are you doing gardening? try another activity.. like knitting, chess, or underwater basket weaving)

To apply, mix 1 cup of food grade diatomaceous earth with 1 gallon of water in a pump sprayer for a wet application. (it will not work until it dries, and will not work if worked into the soil) For dry application, you can use a puffer duster, a dry paintbrush, a shaker (home-made is fine), or the Dustin-Mizer.

Companion Planting for Pest Management


Companion planting is the most basic form of pest control. It involved planting decoy plants to attract pests so they don’t infest your veggies, and synergistic combinations of plants that attract predators of pests of its companion plant. This can get fairly complex, but it can also be very simple. The best part? It is 100% working with nature, with no inputs, no ongoing work, and no potential side effects.

I highly recommend reading this primer on companion planting from Natural News.

10 tips for companion planting for natural pest control and organic sustainability – Increase vegetable yields and improve flavor

Just What is Allowed in USDA Organic Standards?

This is a valid question, in my opinion. I don’t know about you, but we don’t buy organic just because of the label, but because of the substance which the label is supposed to represent. These have been pasted from this downloadable PDF: USDA National Organic Program: Overview of the NOP and the National List

United States Department of Agriculture

Allowed Nonsynthetic (Natural) Pesticide Active Ingredients

  • Pyrethrum
  • Bacteria (e.g.Bt)
  • Spinosad
  • Neemoil /Azadirachtin
  • Diatomaceous earth
  • Plant oils
  • Gibberellic acid
  • Limonene
  • Mined minerals

The positive aspect of the Organic standard, is that there are conditional requirements that must be met that are designed to minimize the need for pest control.

See Code of Federal Regulations, Chapter 7, Section 205.206 (via Cornell University Law School) to learn more.

Organic produce is far superior to conventional produce (mostly for the reasons in the codes linked above), but because of the list of allowable pesticides and the fact that most farms are still growing on a monoculture-like mass scale, I believe that it is of greater benefit to grow your own produce as much as possible. If you control your soil, you control the nutrition value of your food.

– Eat safe. Eat well. Grow a garden.


One thought on “Gardening: Truly Non-Toxic Pest Control

  1. Pingback: But where do you get your protein? – What We Learned This Week

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