DIY Aphid Spray Recipe: How to Make Homemade Insecticidal Soap
Last Updated on July 6, 2024
Are aphids, mealybugs, or other pest insects wreaking havoc on your garden? Come learn how to make DIY aphid spray to get rid of them with this simple homemade insecticidal soap recipe. It’s effective, inexpensive, and easy to make! This post also covers important application tips for the best results.
When mixed and used correctly, homemade insecticidal soap is effective at killing small soft-bodied insects. On the other hand, it’s gentle on your plants, non-toxic to wildlife, and does not harm beneficial insects like ladybugs or bees. Made with natural castile soap, that means this DIY aphid spray recipe is safe for organic gardening. Insecticidal soap can also be used indoors on houseplants.
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RELATED: Get even more organic aphid control tips here, or learn how to get rid of cabbage worms and control grubs in the garden here.
Remember that a garden isn’t supposed to be perfect or free of insects! Above all, we want to encourage a balanced and healthy ecosystem. Following organic gardening practices and companion planting will encourage beneficial insects that naturally pray on aphids, such as ladybugs and green lacewings. I don’t worry when I see a few aphids here and there. Yet when their population gets out of hand, I make a batch of homemade aphid spray.
What Is Insecticidal Soap?
Insecticidal soap, also known as horticultural soap, is a spray used to control small soft-bodied pest insects on plants. It is effective against aphids, mealybugs, spider mites, white flies, psyllids, and scale.
There are many commercially pre-made insecticidal soaps available to buy. However, while those are typically rated for “organic gardening” (and are more environmentally-friendly than most other pesticides) they often still include a long list of chemical ingredients. Therefore, I feel much more comfortable making my own. It’s far cheaper, and about as non-toxic and natural as you can get!
How does it work?
Insecticidal soap works by disrupting soft-bodied insect’s sensitive cell membrane. Essentially, it coats and penetrates the natural protective barrier around their body, which causes them to desiccate or dry out. It kills via pest-specific physical means, not by “poisoning” them.
That means soap spray is NOT effective against insects that have a hard exoskeleton or different anatomy – such as most beetles, ladybugs, crickets, bees, grasshoppers, pill bugs, grubs, or even caterpillars.
Furthermore, homemade insecticidal soap has little-to-no residual effect, and only kills instantly on direct contact. This means that it must be sprayed right onto the target pests to work.
DIY Insecticidal Soap Recipe
You only need two ingredients to make DIY aphid spray: liquid soap and water. Pure natural castile soap is the best choice for homemade insecticidal soap: it’s effective and won’t harm your plants. We use Dr. Bronner’s liquid castile soap. Peppermint Dr. Bronner’s soap provides a further line of defense, since the peppermint aroma deters pests too!
Some old-school gardeners like to use Dawn dish soap, but it has a lot of other ingredients that I personally don’t want on my plants (or to eat). Avoid using soaps or detergents with bleach or degreaser additives, or those intended for the dishwashing machine.
Mixing Instructions
- Simply combine 1 tablespoon of liquid castile soap per quart of water. Mix only what you will use that day.
- For a larger batch, use 5 to 6 tablespoons of soap per gallon of water.
- Shake together in your sprayer to thoroughly mix. Use warm water to promote mixing.
- For light applications, you can mix the soap spray in a classic trigger spray bottle. To treat a larger plant or area, we use my favorite half-gallon pressure sprayer. It holds more spray AND is way easier on my hands! If you re-use old cleaning spray bottles, make sure to thoroughly wash them out before using them in your garden.
Application Instructions
- As with any new plant treatment, it’s best practice to apply it to a small test area a day or two before treating a larger area. Honestly, we’ve never had issues with soap spray – but I have to give you the disclaimer!
- It’s best to apply insecticidal soap in the evening. Do not apply soap spray in direct sunlight, as it can sunburn plant leaves – known as phototoxicity. Beneficial insects are also less active during evening hours.
- Insect soap spray only kills on direct contact, so spray it right on the pests! Coat them thoroughly.
- Turn over or peel open curled-up leaves as needed to access hard-to-reach bugs. I often use my hands to rub the infected areas and leaves as I spray, manually squishing the aphids or mealybugs with my fingers at the same time.
- Let the insecticidal soap soak on the plants for at least 30 minutes.
- Now, you don’t have to rinse off the soap spray after, but I usually like to. It removes soapy residue on your plant leaves, reduces the risk of discoloration, and also washes off the now-dead bugs. Gently spray the plant off with water to rinse (but again, avoid wetting leaves during sunny conditions).
- Re-apply soap spray every 4 to 7 days as needed. It may take several treatments to solve the pest problem.
- Treat early. It is much easier to nip a little infestation in the bud than wait and battle an epic one!
And it’s as simple as that.
I told you it was easy to make homemade aphid spray! Now you can safely battle the pests in your garden in an effective, non-toxic and environmentally-friendly way. I hope you found this article to be helpful. Please feel free to ask questions, or spread the love by sharing this post. May your plants be happy, healthy, and mostly pest-free!
For more tips on organic pest control, be sure to check out our other related articles:
- How to Properly Emulsify Neem Oil & Make a Safe Garden Pest Spray
- Non-Toxic Gopher Control: How to Gopher-Proof Your Garden
- How to Prevent and Treat Powdery Mildew Organically
- How to Identify the Top 18 Garden Pests, and Beneficial Insects
- Over 25 Ways to Stop Pests From Destroying Your Garden
Deanna Talerico
Deanna Talerico (aka DeannaCat) is a garden educator and writer with over 15 years experience in organic gardening. She is a retired Senior Environmental Health Specialist, and holds a M.A. in Environmental Studies and B.S. in Sustainability and Natural Resources.
67 Comments
Pash
Are cucumber beetles considered to be hard-shelled? I’m wondering if the Bronner’s soap spray will work on them. We’re having an infestation. The weekly neem spray may be keeping some of them back, but they’re still propogating like gang busters. Also, you wrote it is best not to spray flowers, is that all flowers, even squash? There are LOTS of those buggers on our squash flowers and also calendula flowers. Thanks in advance! You guys are the best. 🙏
Aaron (Mr. DeannaCat)
Hi Pash, cucumber beetles can be quite the pain and rest assured that we have our fair share over here as well! An organic garden is going to have pest insects but we always hope that there will be just as many predatory insects as well, we just try and create a diverse ecosystem with a variety of plants so that no one particular pest or insect will dominate the space. I don’t think soap spray will work on the beetles but neem oil is supposed to help manage them, I would be cautious about using the neem oil in and around your flowers as you don’t want to spray any bees that may be hanging out inside the flowers, we often have bees sleeping overnight inside of our squash flowers.
There are two different types of cucumber beetles, one that is spotted and one that is striped. The spotted cucumber beetle will feed on over 200 different types of host plants so they have a more varied diet and may not place their full concentration/damage on your cucurbits (squash, cucumber, and melon), they also lay their eggs on grasses so their larvae will typically eat the roots of those plants before emerging as beetles. However, stripped cucumber beetles lay their eggs at the base of cucurbits and their larvae will then eat the roots of those plants before emerging as beetles. As adult beetles, the stripped cucumber beetles also have a strong preference for cucurbits so they will mostly only feed on those plants specifically.
With that being said, beneficial nematodes (hb) are supposed to work on the larvae of stripped cucumber beetles so it could be worth applying those to your soil, either now or waiting until early next year to try and limit their numbers from the beginning. Also using a physical barrier such as floating row covers can help keep them off your plants, however, it will also prevent any pollinators from accessing the flowers unless of course you are trying to manually pollinate yourself. I will typically hand pick beetles when I am around the plants but we haven’t resorted to any other control or preventative measure. Hope that helps and good luck!
Pash
Thanks, Aaron. This is reasuring and helpful. Especially glad to hear that we’re not alone with this problem and also great to learn about bees sleeping in the flowers! I suppose squash beetles too would not be affected by soap spray? Those dudes are starting to multiply too. We have applied two loads of beneficial nematodes across the garden, which seems to have curbed the cutworms and lessoned the number of peel bugs dramatically. But the darned cucumber beetles are thriving. I’ve been doing a neem foliar spray with two tablespoons of neem and 2 Tbls of Bronners in 2 gallons of water, once a week. Can I safely up the amount of neem and/or soap, and spray everything down more often?
With gratitude.
Aaron (Mr. DeannaCat)
Hi Pash, you definitely aren’t alone at all, going forward, the recommended practices is to also rotate where you plant your cucurbits each season in hopes of reducing the cucumber beetle population from the start. That’s great to hear the beneficial nematodes seem to be helping for your cutworms but the soap spray will likely have little effect on the squash bugs as well. In regards to your neem oil sprays, you can increase the amount of soap you add to the mixture by a tablespoon or two but I wouldn’t add any more neem oil as the recommended amount is 1 tablespoon per gallon, you could end up harming your plants if you add much more than that. Spraying once a week is considered a preventative measure but during an infestation, you can spray up to two times per week in hopes of knocking down the population. Hope that helps and have fun growing!
Marcia Pearl
Thanks for reminding me to use peppermint soap to control aphids in the garden. I use Dr. Bronners liquid soaps for personal hygiene and absolutely love the scent of the peppermint, lavender, and eucalyptus varieties. There are multiple uses listed on the label, what a wonderful product! I’m going to mix and use the peppermint soap spray for the garden this evening. Can’t wait!
Aaron (Mr. DeannaCat)
Good luck Marcia, we just had to give a few plants a soap spray last night as well as the aphids were getting out of hand.
Pash
In your experience, if you just rinse off aphids with a hose, won’t they just move on to other plants or return to their original home that you rinsed them from? Thanks.
Aaron (Mr. DeannaCat)
Hi Pash, in our experience, spraying them off with water works but it usually needs to be done on somewhat of a schedule as it doesn’t prevent aphids, it just manually removes them. We haven’t noticed it cause the aphids to migrate to other plants in our experience.
jean mcconkey
great site with clear easy directions.
as an organic nursery owner, I just want to say if a plant is being decimated by bugs, there is often a nutritional component. There are some new foliar sprays one called photo mag that has been a game changer for me.
I could never grow squash plants because of the squash bugs and borers. I might get one or two squash before they destroyed the plants.
This year after taking a break for about 5 years, I used a cloth crop cover and also sprayed photo mag every week.
I was blessed with beautiful zucchini with those two changes. The plants were the healthiest and biggest that I have ever seen.
Aaron (Mr. DeannaCat)
Thanks for sharing Jean, so glad you were successfully able to grow squash last summer and hopefully there will be bountiful harvests this year as well!