Step 1: Fill the jug with water.
Fill a 1-gallon jug with water, either distilled or tap, until it is hard water (hard water reduces the effectiveness of disinfectant soap), and leave two inches at the top. Sometimes, the easiest way to do this is to buy a gallon of distilled water at the grocery store—not mineral-enhanced water—and label it with an indelible marker to make sure the solution isn’t mistaken for anything else.
To spray large areas with a pump type garden sprayer, fill the spray container itself with water, but stick to the following ingredient ratios we provide. Typically, pump sprayers hold 1 to 3 gallons of water, and most have a fill line near the top that indicates how many gallons are in the container.
Step 2: Add soap and oil.
Then add 2 1/2 tablespoons of mild liquid soap, or Liquid dish soapand 2 1/2 tablespoons vegetable oil. Coconut oil makes a great alternative to regular vegetable oil, and olive or grapeseed oil are also suitable. Both the liquid soap and the oil act as surfactants to help prevent the solution from dripping off the plant leaves. The longer the solution stays on the plant foliage, the better the chances of killing the invading insects. Don’t overdo the soap or oil ratio, though—it should be a very mild solution to protect the plant.
Step 3: Shake the jug and pour the solution into the spray bottle.
Screw on the lid, shake the solution to distribute the ingredients and immediately pour the solution into the spray bottle. Shake the jug each time you refill the spray bottle to maintain the correct ratio of ingredients so as not to apply too weak or too harsh a formula. Likewise, shake the spray bottle well frequently while spraying to keep the solution mixed.
If any leftover DIY disinfectant soap solution has been sitting on the shelf for more than a month between uses, check to make sure it’s still viable. Occasionally, the oil in the solution may go rancid, causing the solution to appear slightly cloudy or smelly. The best solution is to mix a fresh batch.
What to consider before using insecticidal soap
Although insecticidal soap is safe for many flowers and vegetables, some plants are sensitive to the solution and can cause leaf damage. The most susceptible plants include sweet peas, begonias, impatiens, azaleas and rhododendrons. If it’s your first time treating a plant and you’re not sure if it’s safe to use an insecticidal soap, err on the side of caution and do a sensitivity test first. Spray the solution on only two or three leaves of the plant, and then check the plant after 24 hours. If the leaves are dry, do not treat the plant with insecticidal soap. But, if the leaves look as healthy as before, it is safe to spray the remaining parts regularly.
When used as directed, insecticidal soaps will not harm pets, birds or wildlife. That said, it presents little risk of toxicity to fish, so it’s not advisable to treat aquatic plants or plants near fish ponds.
How to use disinfectant soap
Spray an even mist of insecticidal soap Garden insects Usually hide under the leaves and along the main stem of the plant. The goal is to cover all plant surfaces with enough spray to wet the leaves, but you don’t need to use so much that the solution drips off the leaves. Because this mixture is eco-friendly, it is safe to spray directly on fruits and vegetables such as peaches, apples, tomatoes, zucchini and pumpkins.
Repeat application every 4 to 7 days as needed. Because insecticidal soap only kills insects when wet, it is a good idea to treat plants early in the morning or late in the evening when the solution does not evaporate as quickly in the heat of the day.
FAQ
Sure! By mixing 2 1/2 tablespoons of vegetable oil and 2 1/2 tablespoons of pure liquid soap with 1 gallon of distilled water, you will have a full gallon of insecticidal soap to safely spray plants in a flowerbed or vegetable garden.
Many gardeners successfully use Dawn as a liquid soap in their insecticidal soap solution, but unlike pure soaps like castile, Dawn contains artificial colors and ingredients. While it may not harm plants, using a soap that does not contain fragrance or other artificial ingredients may be a more eco-friendly option.
Both household and commercial disinfectant soaps can be beneficial. For those looking to buy ready-made insecticidal soaps that are safe to use on plants, consider Garden Safe Insecticidal SoapWhich is safe to use on all plants including vegetables.
If the percentage of soap in a homemade insecticidal soap solution is too high, the risk of plant damage increases. It also increases if the liquid soap used to make the solution contains other chemicals or ingredients. For best—and safest—results, stick to natural liquid soaps and don’t vary from the recommended ingredient ratios.
For general pest protection, spray the plant thoroughly with an insecticidal soap once a week. After heavy rains, reapply the spray.
Several natural pesticides exist that are effective and safe for use on plants, including Neem oil and diatomaceous earth. However, it is not an ingredient in disinfectant soaps. Disinfectant soap contains only water, liquid soap and oil.
Final thoughts
Plants naturally attract bugs—some bugs perform beneficial functions in the garden, such as pollinating flowers or killing harmful insects. However, no gardener wants to lose an entire crop to an insect infestation, and using an insecticidal soap is a great way to keep harmful insects at bay while protecting the plants.
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