Anyone who has cared for a plant can tell you that it’s not the Garden of Eden out there. Bad things happen to our beloved plants. Most of the time that comes in the form of sucking or chewing insects. You can’t ask them nicely to leave or fence them out so what do you do?
Unfortunately, an infestation of damaging insects often requires using “deadly force” in the form of an insecticide. However, in recent decades we have realized that many insecticides do not discriminate between good and bad bugs, making them a poor choice for the organic gardener. They will just as easily kill a ladybug or butterfly (good guys) as quickly as an aphid or a thrip (bad guys).
Meet the dreaded Public Garden Enemy No. 1, the common garden aphid. The tiny insects love to munch on annuals and new growth on perennials.
A Safe Insecticide
The answer to our problem is insecticidal soap for three reasons. First (and most important) it only kills by direct contact. Once sprayed and dried it stops being deadly, unlike poisons. Second, the chemical elements break down naturally in a short time and leave no long-term damaging residue in your garden. Third, the liquid solution is no more deadly than a bar of soap. If sprayed on herbs or vegetables the residue easily washes off, leaving your produce safe to eat and enjoy.
So how does insecticidal soap perform all this magic? It works by washing off the waxy shell cuticle that surrounds all soft-bodied insects. Once that cuticle is gone the insect dies of dehydration. What you have left is a dead sucking insect and a little bit of dried soap. Perfect!
There are several commercial insecticidal soaps on the market but thrifty gardeners sometimes like to make their own. The basic formula is 1-4 tablespoons of liquid soap for each gallon of water. Place in a spray bottle and go after those bad bugs.
Insecticidal soap kills by contact, not by poisoning the insect. This is good because it leaves no lasting harmful residue in your garden. The only caution I would give you is to focus your spraying on insects you know are damaging. Don’t spray it everywhere as a preventative because you may be killing beneficial insects – like aphid-eating ladybugs – thus doing more harm than good.
Many damaging insects take cover on the underside of leaves. When applying insecticidal soap, always get the underside of leaves and stems.
Making Your Own Insecticidal Soap
Insecticidal soap can be made at home with liquid soap you have around the house. Combine one tablespoon of liquid soap (not detergent or soaps with bleach or de-greasers) with one quart of water and place in a hand sprayer. Spray on damaging bugs from 8-10 inches away. Remember to spray the underside of leaves and stems to get all the little nasty critters.
My only word of caution to you is that home-made soaps will kill insects but they also can harm delicate plants. Like insects, plants also have a waxy film on the leaves that may be removed by the insecticidal soap. If this happens you will see leaf damage. Test your home-made soap first on a part of a plant and watch for leaf damage during the first 24 hours after spraying.
The thin webbing on this plant is from spider mites, not beneficial garden spiders. If you see this on your plants, it’s time for insecticidal soap.
So what’s better? Home-made or store-bought? For my garden, I spend the few bucks and use commercially formulated insecticidal soap. Commercial insecticidal soaps are formulated to minimize potential damage to plants. One bottle of spray will last me about two years for my average-sized garden.
Whether store bought or home-made, insecticidall soap is safe, effective, and leaves virtually no harmful residue. That’s what makes it the “go to” solution for organic gardeners.
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