Homemade Pesticides: A Word of Warning

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20180210A moziru.com

Be careful when using homemade pesticides: they can be lethal! Source: moziru.com

Be very careful with the homemade pesticide recipes that circulate in amateur gardening circles. Yes, they can sometimes be effective, but often they are nearly worthless. Worse, there are cases where the pesticide is so toxic that the person who applies it becomes sick or can even die.

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Nicotine pesticides can be deadly to humans: there is no logical reason to want to use them. Source: laidbackgardener.blog

A telling case: nicotine insecticides. These were withdrawn from the market in most countries some 30 years ago because of their toxicity to humans (although they’re still sold in some countries, notably India), but ever since, recipes for nicotine pesticides have been abundantly seen in print and on the Internet. Usually they involve making a decoction by soaking cigarettes, cigarette stubs, or tobacco leaves in water for a given length of time, then spraying this product onto plants to kill insects. The same people who kindly share this information ought to also mention that a few spoonfuls of such a decoction can kill a child!

Be Careful When Applying Any Pesticide

I’m not trying to prevent you from using or making homemade pesticides, but any time you use a product because you believe it is toxic to insects or diseases, it is quite possibly also toxic for humans and should be used accordingly.

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Strychnine, now banned or severely controlled in most countries because of its extreme toxicity to humans, is nevertheless biological. Source: http://www.wired.com

Never forget that biological pesticides are often as toxic as chemical pesticides: a poison remains a poison, whatever its origins. Strychnine, for example, is derived from a plant (Strychnos nux-vomica) and yet it is one of the most virulent poisons known. Agatha Christie often had her characters rummage in the garden shed for it, as it was once a common pesticide, now banned in most countries.

Safe or Not?

One way of reasoning about a homemade pesticide’s possible toxicity is to ask yourself if the ingredients are normally toxic to humans.

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Garlic is not toxic to humans and can make a safe homemade pesticide as long as you use it fresh (if stored too long, harmful bacteria could develop). Source: Donovan Govan, Wikimedia Commons

Homemade pesticides made from garlic, soap, hot peppers, baking soda, milk, etc. probably won’t be too toxic (at least when they are used fresh and properly diluted) because their ingredients are normally harmless to humans when used appropriately. Still, they can be irritating to the skin and the eyes, so protective clothing is always recommended during application.

Decoctions made from poison plant parts, such as rhubarb or potato leaves, on the contrary, are indeed biological, being derived from plants, but ones that are known to be toxic to humans: they should be used with caution and kept out of the reach of children and pets.

Pesticide Avoidance

Personally, I try not to use pesticides, whether chemical or biological, when gardening. My main treatments against insects and diseases are:

1. Plant varieties that are naturally resistant to insects, slugs and diseases.
2. Spray infested plants with water to (hopefully) reduce the number of pests;
3. Pull out and destroy the infested plant before it infects its neighbors;

That’s mighty simple advice, but usually surprisingly effective!20180210A moziru.com.jpg

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Gardening Tip: If It Ain’t Broke, Don’t Fix It!

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20170408E.jpgHere’s a principle about laidback gardening that I don’t emphasize nearly enough: “If it ain’t broke, don’t fix it!”

When a plant performs well for you or a gardening technique works in your case, even though experts say it shouldn’t, don’t change anything. And that applies even if I’m the so-called expert!

Plants and gardening are full of surprises and often things that shouldn’t work do. For example, I’ve seen:

  • Roses blooming quite nicely in a woodland even though “everybody knows” that they need to be planted in full sun.
  • Lavender (Lavandula angustifolia) positively thriving in zone 3, whereas in theory it’s not reliably hardy beyond zone 5.
  • African violets full of flowers that their owners claimed were fertilized with…birth control pills!

The gardening world is jam-packed with these exceptions. Sometimes really good overall garden conditions can compensate for a weak point, for example, but other times the result is simply a total mystery. However, if it works, does it matter? Just keep on trucking!

He Said, She Said

Of course, sometimes conflicting gardening advice is simply due to two different points of view on how things should be done and both methods work. Here’s one example.

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Sure you can root cuttings in water… but you’ll get better results if you root them in potting mix.

It’s easy enough to prove that softwood cuttings root significantly better when rooted in potting soil under high humidity (under a plastic dome or inside a clear plastic bag) then when placed in a glass of water. Try a side-by-side experiment at home with cuttings from the same plant and you’ll see: soil-grown plants started “under glass” (the term used for starting them inside a mini-greenhouse) inevitably grow faster with greater vigor and are less subject to rot than cuttings rooted in water. But cuttings rooted in water often do well enough too, especially easy-to-root plants, like philodendrons and coleus. So, if it works for you, keep at it!

Just Don’t Poison Anybody

I have a hard time, however, stomaching home remedies that could have serious consequences… and there are a surprising number of them. Yes, they often work, but the risks just aren’t worth taking.

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Insecticide made from cigarette butts: who are you trying to kill? The pest or yourself?

For example, homemade nicotine insecticides, popularly made from tobacco or cigarette butts, are just too toxic to be used safely. Imagine! A spoonful of many of these homemade concoctions could easily to kill a child! Yet there are still many people who use such nicotine pesticides without even wearing protective clothing. If that’s your case, may I suggest you stop immediately?

Another example is the popular technique of placing mothballs in the garden to keep away cats, groundhogs, deer, etc. Yes, it may sometimes be effective and you may be pleased with the result… until your dog eats them and dies. And young children in the neighborhood could mistake them for candy! No, the risk is just too great!


When you garden, no, you shouldn’t mess with success. As long as you’re pleased with the results, just keep at it… but do make sure what you’re doing is safe!20170408E

Homemade Pesticides: A Word of Warning

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20150203Be very careful with the homemade pesticide recipes that circulate in amateur gardening circles. Yes, they can sometimes be effective, but often they are nearly worthless. Worse, there are cases where the pesticide is so toxic that the person who applies it becomes sick or can even die.

A telling case: nicotine insecticides. These were withdrawn from the market in most countries some 30 years ago because of their toxicity to humans, but ever since, recipes for nicotine pesticides have been abundantly seen in print and on the Internet. Usually they involve making a decoction by soaking cigarettes, cigarette stubs, or tobacco leaves in water for a given length of time, then spraying this product onto plants to kill insects. The same people who kindly share this information ought to also mention that a few spoonfuls of such a decoction can kill a child!

I’m not trying to prevent you from using or making homemade pesticides, but anytime you use a product because you believe it is toxic to insects or kills diseases, it is quite possibly also toxic for humans and should be used accordingly.

Never forget that biological pesticides are often as toxic chemical pesticides: a poison remains a poison, whatever its origins. Strychnine is derived from a plant, for example, and yet it is one of the most virulent poisons known.

One way of reasoning about a homemade pesticide’s possible toxicity is to ask yourself if the ingredients are normally toxic to humans. Homemade pesticides made from garlic, soap, hot peppers, baking soda, milk, etc. probably won’t not be too toxic (at least when they are used fresh and well diluted) because their ingredients are normally harmless to humans when used adequately. Still, they can be irritating to the skin and the eyes, so protective clothing is always recommended during application. Decoctions made from rhubarb, tomato or potato leaves, on the contrary, are indeed derived from natural products, but ones that are known to be toxic to humans: they should be used with caution and kept out of the reach of children and pets.

Personally, I try not to use pesticides, whether chemical or biological. My main treatments against insects and diseases are:

1. Rinse plant with clean water to (hopefully) reduce the number of pests;
2. Pull out and destroy the infested plant infested before it infects its neighbors;
3. Plant varieties that are naturally resistant to insects, slugs and diseases.

That’s mighty simple advice, but usually surprisingly effective.