Insect Repellant Tips: Making Homemade Insecticidal Soap

For those gardeners who are plagued by insects devouring their plants, homemade insecticide soap is easy to make.

Nothing is more satisfying than a beautiful garden in full bloom, and nothing is more frustrating than seeing it devoured. Whether you are a full-fledged gardener or just keep a few potted herbs on the porch, chances are that your plants have suffered from insect infestation. There are plenty of commercial insecticides available to kill these pests, but some people prefer a more organic solution to the problem. For these gardeners, it is possible to make a homemade insecticide soap that is also safe for people and pets.

All soaps are the result of fatty acids (either from animal or vegetable sources) reacting with an alkaline substance like lye. The process, called saponification, creates a product that is cleansing, insecticidal, and potentially even herbicidal. Commercial insect-killing soaps are undisputedly effective, but many gardeners dislike using them. If food plants are sprayed too near harvest time, consumers may be exposed to significant levels of dangerous chemicals. Some of these products may cause skin irritation or illness and can be dangerous to pets. Alternately, homemade insecticide soaps are non-toxic for plants and people, can be used on vegetables and fruits up to the point of harvest, and are unlikely to be phototoxic to plants unless they are used excessively. For all these reasons as well as to save time and money, you may wish to prepare your own insecticide soap at home.

Which Soap Is Best?

The best type of soap for killing insects is debatable; some recommend pure castile soap or liquid hand soap (like Ivory), but others endorse various name brand liquid dish liquids (most often Dawn and Ivory). Detergents are good choices because they are not affected by minerals in hard water, unlike non-detergent soaps. However, detergents are reputed to be more damaging to plants if used excessively. If you choose to use a dish detergent, make sure to rinse your plants within an hour of applying the insecticide. Also, do not spray plants on very hot or humid days, as the plant will be more prone to burning. Always test a small area of the plant that is not too visible before applying and insecticide. Some species, especially those with lightly colored foliage, are more likely to be burned by soaps.

Soap Insecticide Recipes

A one to two percent concentration of soap in water is an appropriate dilution for insecticide soap. This mixture will kill insects without risking burning the plant. This equates to approximately five tablespoons of soap per one gallon of water. Most recipes recommend using two teaspoons of dish detergent per quart of water, while those who use castile soap should add one or two tablespoons per quart of water. Blend the ingredients in a large pot or bucket, and then transfer them to a spray bottle as needed. The mixture will keep indefinitely. You may also wish to add some herbs known to repel, if not kill, many common garden pests. Try a handful of any of the following: horseradish, cayenne pepper, garlic, or onions. Make a diffusion by pouring hot water over the plant of your choice, sealing it in a container overnight, and straining it. Add the spice-infused water to a basic soap insecticide for its extra repellant properties. Again, make sure that you test a small area of the plant before you douse it with the spray, as some plants are very sensitive to these spices.


The reason that soap kills insects effectively is that they penetrate and disrupt the natural balance of their cells. The bug's cell respiration will fail, killing it almost immediately once it has been exposed. It is therefore important to spray the insecticide directly on pests, saturating them thoroughly. Spray every bit of the plant with the soap insecticide, paying special attention to intersections and the undersides of leaves where pests hide and lay eggs. Once the soap residue has dried on the plant, it will lose its insect-killing properties. Rinse off the film and reapply about once a week until no signs of infestation are visible. Soap insecticides only kill small, soft-bodied insects like aphids, spider mites, white flies, mealybugs, and immature scales. They will also destroy all eggs, including those of moths, flies, and beetles, as well as very small larvae. Larger pests (Japanese beetles, maggots, and caterpillars, for example) will be unaffected. For this reason, adding an all-purpose repellant to the mixture may be beneficial. Otherwise, you may have to resort to commercial products to eradicate these pests.

As gardeners, we are as concerned about the safety of our pets, our environment, and ourselves as the health and beauty of our plants. Making a nontoxic and inexpensive insecticide is one way that we can protect all of these things. From the vegetable patch to the houseplant, all of the green growing things that people love can be spared the fate of being an aphid's lunch. Better yet, those who grow them can take pleasure in how inexpensive and eco-friendly their homemade soap insecticides are.

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