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Natural alternatives to pesticides still toxic

A growing number of people call our office inquiring about natural alternatives to pesticides every week. This is not a local phenomenon. Nationwide, homeowners and gardeners are choosing natural alternatives to solve their pest problems.
ic0104141.jpg Pablo Kalnay

In my opinion, this is a good sign. Any reduction of unnecessary chemical pesticide use is a step in the right direction. But we have to keep in mind that "natural" does not mean "nontoxic."

Several natural products used in the past were considerably more toxic than most of the chemical pesticides we use today.

Strychnine, an alkaloid extracted from the tree Strychnus nux-vomica, was used for many years as a rodenticide. Just 0.02 ounces of strychnine is enough to kill a 155-pound person, making strychnine (rat poison) a favorite silent killer in real and fictisious murders.

Nicotine, a broad-spectrum insecticide extracted from tobacco leaves, is also highly toxic. One tenth of an ounce of pure nicotine in your mouth and you are history. These pesticides lost their appeal because of their toxicity and are no longer in use. Some people still make their own nicotine extracts, which I strongly discourage because nicotine is readily absorbed through the skin. There are other natural alkaloids, less toxic than strychnine and nicotine, commercially available as pesticides. Rotenoids, extracted from the Derris tree root, and ryanoids, from the ryania shrub, are just two examples.

Pyrethrum, extracted from the flowers of Chrysanthemum cinerariifolium, was the poster child of ic0104142.jpg low-toxicity natural pesticides for many years. This insecticide offers excellent control against many household pests while its toxicity to humans and pets is quite low. Several synthetic insecticides have been derived from it. They are called pyrethroids. It is worth mentioning that some pyrethroids are even less toxic to humans than their natural counterpart. Neem, an extract from the seed of the Neem tree (Azadirachta indica), native to India, is another natural pesticide that has gained popularity recently. It is intended for outdoor use. Neem, an insect growth regulator that prevents some insects from completing their life cycle, presents very low toxicity to humans.

A couple of natural pesticides of a different nature are boric acid and diatomaceous earth. Boric acid is an inorganic insecticide. It was very popular in the thirties and forties and has regained popularity during the last decade or so because it has low toxicity to humans and will remain effective against pests like roaches as long as it stays dry. Diatomaceous earth consists of the fossilized remains of algae (diatoms). It is a physical insecticide. It acts by physical contact, not by ingestion or absorption and is very effective against household pests such as fleas or roaches. Dusting these products in cracks and crevices can offer longlasting control of household pests without a serious risk to the people living there, if properly used.

The natural pesticides I mentioned here are commercially available and they all come with a label. Always keep in mind: no matter how "natural" they are, they are still pesticides. Always read the label and follow it to the letter. Popular make-it-yourself pesticide recipes may look like they're fun and environmentally sound, but you may end up with a dangerous concoction. Use your common sense and remember: there is no such thing as a completely safe pesticide. A pesticide, in order to be effective, has to kill something.

Let me finish with a few words of advice about controlling pests. Before you do anything, make sure that have properly identified the problem pest and that the solution makes sense. Many times the sensible thing to do is NOT to do anything at all.

Pdblo Kalnay is a visiting extension educator for integrated pest management at the University of Illinois Extension Springfield Center, P.O. Box 8199 Springfield, IL 62791, (217) 782-6515, e-mail:


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