Here’s everything you need to know about how to use insecticidal soap to control insects. This is an effective and organic method for controlling aphids and other soft-bodied insects.
Understanding and using insecticidal soaps properly will help you manage pests organically, both indoors and out. As you know, not all pesticides are alike. Some chemicals are more toxic, killing a broad range of species, while others are less toxic and more targeted. Insecticidal soaps are among the more targeted pesticides. They have limited impact on beneficial insects, birds, reptiles, fish, and other wildlife (including humans). By understanding and using insecticidal soaps effectively, you can combat common plant pests while protecting beneficial organisms.
Why Use Insecticidal Soap?
Break down the name and you see that insecticidal soap is literally a soap that kills insects. Insecticidal soaps offer a safe, effective, less-toxic alternative to harsh chemicals for managing garden and houseplant pests. The active ingredient is potassium salt of fatty acids, also called soap salts. Insecticidal soaps kill by suffocating insects. These soaps also appear to remove the protective waxes that cover an insect, causing dehydration.
To make it easier to purchase the insecticidal soap products mentioned in this story, we have included direct links to the products. Home Garden and Homestead is a member of the Amazon affiliate program, and we receive a small commission (at no cost to you) from qualified sales generated by these product links.
What Pests Do Insecticidal Soaps Target?
Insecticidal soaps are effective against small, soft-bodied arthropods, such as aphids, young scales, whiteflies, thrips, mealybugs, and spider mites. Most larger insects, including many pollinators and predators such as lady beetles, green lacewings, and bees, are not very susceptible to soap sprays.
NOTE: It is important to know that insecticidal soaps kill predatory mites. These small arthropods are often important in controlling spider mites. They also feed on the eggs and early life stages of thrips, whiteflies, and scale insects.
How to Use Insecticidal Soap to Control Insects
To be effective, insecticidal soaps must be sprayed directly on the target pest. Apply by spraying the tops and undersides of infected leaves. Do this in the morning or late in the day to slow the drying time of the soap. When you use insecticidal soap to control insects, understand the soap is ineffective once it dries. So, repeat applications every 4-7 days may be necessary.
Insecticidal soaps can also be used to wash honeydew and sooty mold from leaf surfaces. They are safe to use on fruit and vegetable crops up until harvest. Watch for and avoid spraying on beneficial insects when applying.
Insecticidal soaps are available as either a concentrate or pre-mixed in a ready-to-use spray bottle. Always follow the directions on the label for proper dilution and application. Calcium, magnesium, and iron found in hard water reduces the effectiveness of insecticidal soap. If you have hard water, use bottled water to dilute concentrated insecticidal soap.
Use Insecticidal Soap and Avoid Plant Damage
One drawback to using insecticidal soaps is their potential to cause plant injury, called phytotoxicity. Some plants are sensitive to soap sprays and may be seriously injured. The product label will list plants sensitive to the product. If you are uncertain, you can test the soap on a small area of the plant. Wait 24 hours to see if any damage occurs before spraying again.
Water-stressed plants are more sensitive to phytotoxicity. Make sure plants are well hydrated before treatment. High temperatures and humidity may also increase plant stress and sensitivity. Do not use soaps, including homemade products, when the temperature exceeds 90 degrees F.
Can I Make My Own Insecticidal Soap?
Insecticidal soaps are chemically similar to liquid hand soaps, and many gardeners mix their own insecticidal soap at home. However, there are features of commercial insecticidal soap products that distinguish them from other soaps. Insecticidal soaps sold for control of insects are specifically selected to control insects while minimizing plant injury.
Certain brands of hand soaps and liquid dishwashing detergents can be effective as an insecticidal soap. But they are not designed for use on plant,s and there is increased risk of plant injury with these products. Using commercially prepared insecticidal soaps instead of homemade solutions is highly recommended.
Insecticidal Soap Mixtures
Before you use insecticidal soap to control insects, it is important to read the product labels. Some formulations include insecticidal soap along with an additional active ingredient such as botanical or microbial insecticides. For example, Captain Jack’s Insecticidal Super Soap contains Spinosad. Spinosad is derived from a soil-dwelling bacterium used to control insect pests including caterpillars, thrips, spider mites, and beetle larvae.
Garden Safe Houseplant and Garden Killer contains pyrethrin, a chemical produced in the flower heads of certain chrysanthemum species. Other products might contain neem oil or sulfurs. Finally, Safer Brand Insect Killing Soap contains seaweed extract to improve plant health while treating pests.
While these products are all organic insecticides, each impacts beneficial organisms differently. Be sure to pay close attention to the product you are buying and find the one that best matches your goals.
When you use insecticidal soap to control insects, you are using an eco-friendly way to kill insect pests. There are additional environmentally friendly options, including organic horticultural oil.
Also remember to keep an eye on your plants and regularly check them for insect pests. Catching an insect problem before it can become a major infestation is a great way to keep plants healthy and happy!