Insecticidal Soap

Q: Could you please advise if insecticidal soap is a healthier way to treat pests on plants, trees, etc. than using other chemical pesticides? Is the soap gentler on the greenery?

A: I think we have to get away from using the words “chemical pesticide”. I’m sure you realize that soap (whether insecticidal or the hand-washing kind) is a chemical too. Soap (as opposed to a detergent) is the product of a reaction between a strong alkali (like potassium hydroxide) and a fat or oil. There are many kinds of soap, all dependent on which chemicals are used in the initial reaction. Some are dangerous to use but some are so gentle they can be applied to a baby’s bottom!

Insecticidal soap kills bugs by dissolving their waxy coating. The insects subsequently dry out and die. On the other hand, you may sometimes see herbicidal soap for sale. It is designed and manufactured to kill plant leaves. Insecticidal soap has been tested on plants and has been found not to harm their cells.

I’m sure you have heard of gardeners who mix up their own home-brew of kitchen soap/detergent to spray on insects in their landscape. In my view, this is dangerous unless they first test the spray on an expendable plant to be sure it is not herbicidal in effect.

The bottom line is that I often use insecticidal soap, not because it is “safer” but because it is effective in controlling young insects. Insecticidal soap won’t kill hard-shelled insects, like Japanese beetles, but it quickly kills aphids. I don’t see the need to use a synthetic “chemical” insecticide in all cases. Insecticidal soap is just another tool in our arsenal of pest control products.