Insecticidal soap is helpful for all plant enthusiasts and gardeners to have on hand. Not only can insecticidal soap be used to control damaging insects, it’s extremely easy to make. While some pesticides can be dangerous to plants, animals and humans, insecticidal soap is much more eco-friendly.

So how does it work? Made from the fatty acids of plants, insecticide soap disrupts the cell membranes of insects, killing them. It works on insects like aphids, spider mites, whiteflies and scale.

While being eco-friendly is a major perk, insecticidal soap can save you money depending on how many plants you tend. Lindsey Hyland, a gardening expert and founder of Urban Organic Yield, estimates making one gallon of insecticidal soap can cost you as little as $5. For comparison, commercial insecticidal soap can cost $20 to $35 per gallon. Plus, insecticidal soap can be used on indoor and outdoor plants.

How To Make Insecticidal Soap

Making one gallon of insecticidal soap takes less than 10 minutes. Hyland swears by this insecticidal soap recipe, which she makes at home and uses in her garden.

Ingredients

• One gallon water;
• One cup dish soap (Hyland prefers Dawn, but Castile soap can be used instead);
• 1/4-cup vegetable oil.

In a medium-sized bucket or container, mix the water, dish soap and vegetable oil with a paint stir stick or large mixing spoon. Stir until the ingredients are well combined. Use a funnel to pour the mixture into unused or well-cleaned spray bottles. Store filled spray bottles in a cool, dry place.

How To Use Insecticidal Soap

Before using insecticidal soap, make sure plants are watered and well-hydrated. Wilted plants generally don’t take well to pesticides.

It’s also a good idea to spray one plant first to make sure it tolerates the mixture well. A plant that’s sensitive to insecticidal soap will likely show burned or scorched spots on its leaves within 24 hours of spraying. If this happens, try diluting the solution by adding 50 percent more water.Damage after dilution generally indicates that the plant can’t tolerate insecticides.

Following a successful test run, move on to other plants as needed. “I find it’s best to apply it in the morning or evening, when the sun isn’t too strong,” says Hyland. Insecticidal soap tends to work much better when it’s wet out, like after a rain, or with morning or evening dew.

To use, spray the solution on any plants with unwanted bugs. Then repeat as necessary — ideally, once a week. Each plant should only need a few sprays. “When spraying indoor plants, it’s important to avoid contact with the leaves as it will cause them to yellow and/or fall off,” Hyland says.

For all indoor plants, carefully spray the stems instead. For outdoor plants, spray both leaves and stems. In both cases, try to avoid spraying any budding flowers.

As a safety precaution, Hyland recommends wearing a mask when spraying to avoid inhaling the product, which can cause nose and throat irritation. “It’s also a good idea to avoid contact with your skin, and wash your hands thoroughly after use,” she says.