DIY Aphid Spray Recipe: How to Make Homemade Insecticidal Soap
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
71 Comments
Kelly P
Hello! This looks so easy – can’t wait to try it. We have had a ton of Spotted Lantern Fly nymphs on the fig tree. Do you think this would work against them? I don’t want them to grow up but don’t want to use anything harsh on my fruits and veg! Thanks!
Aaron (Mr. DeannaCat)
Hi Kelly, we aren’t too familiar with having to deal with Spotted Lanternfly’s, but I would check out this extensive article by Penn State which has various methods of control depending on severity of the infestation. Hope that helps and good luck in your garden.
John G
You guys are very helpful! Just drenched my plants with the 3%, 4:1 hydrogen peroxide mix for the gnats. I think I will use it instead of Neem oil from now on. I will mix up and use your peppermint soap mixture as well when I see any further soft-bodied insects on the plants. If I understand it correctly, I can use the soap on the buds as well. You say that this is only used once the buggers show up but is there something to use on buds as a perventitve spray or do you recommend just doing the preventative measures until something shows up? If I see catepillers then the BTi should be used? Is it safe on the buds as well?
Once again, very helpful information… Thank you.
Aaron (Mr. DeannaCat)
Hi John, you likely won’t have to worry about caterpillars if you are growing indoors so you won’t need to use BT, however, if growing outdoors you would likely need to and it can be applied to the flowers throughout their growth cycle if needed. As far as preventative, I typically mean using IPM sprays throughout the vegetative cycle and into the first few weeks of flower. However, once you get past the 3rd week of flower or so, I try not to spray anything on the flowers themselves (aside from BT if growing outdoors and have bud worm issues). You could spray the soap on the flowers but I would try to avoid it as it will leave a soapy residue and may effect the flavor as well. Some people choose to wash their buds after harvest, especially so if growing outdoors due to bugs, dirt debris, etc. and that may help wash off some of the soap as well.
My IPM spray for preventative measures is a neem oil spray once a week throughout the vegetative cycle and into the first 2-3 weeks of flower and that is it for indoors. If I am growing outdoors I will then switch to a weekly or bi weekly BT spray as they can destroy your harvest where we are located. Hope that helps and good luck!
Edward Halverson
I have plants that are doing really well. About 35 days old and in the house.
Would it be a good idea to give them some soap water now?
Or is it just when you start seeing bugs later when they are outside?
Thank you!
Aaron (Mr. DeannaCat)
Hello Edward, we typically only apply the soap spray when we see an active infestation of aphids or other soft bodied pest insects as it needs direct contact to be effective. Hope that helps and good luck with your seedlings!
Sharon
I am getting slammed this year in our new house. And it is like overnight it is fine and then covered with army worms that BT is barley touching on the Swiss chard. Then today all my kale is white with white flys. So hard to wash off. I am going to try the bronners soap. But am thinking because I have so many winter greens growing about using neem. Plus that bed has given me some problems with mildew. Will that help prevent it? And the bottle you recommend is pretty big. Does the neem spoil?
You guys have been so helpful thank you and o love seeing the pictures of my home area. Thank you.
Aaron (Mr. DeannaCat)
Hi Sharon, that is too bad you are getting hit with so many pests at once. The neem will last for at least a year and I would only use it on the greens if you plan on not eating any of the greens for a couple weeks. We don’t have to deal with army worms but BT should be able to take care of them, I would apply BT at least once a week to keep them under control, apply it at night or just before the sun goes down as sunlight can make the effective portion of BT dissipate more quickly. Also, as far as your white fly issue goes, I would first just stick with the soap spray and see how that goes. Apply it a couple times a week if the white flies are still sticking around. You can always rinse off your greens on the days in between soap sprays if there is excess on the plants as it should take care of the flies on contact and doesn’t off much after that. I would stick with the two options that were just mentioned before treating the plants with neem oil although we have found that it seems to help prevent mildew. Hope that helps and good luck, let us know if anything else comes up.
Sharon
Help! I have used the spray for the white flys and it is helping on the kale. But they are covered in eggs. The kale still looks perfect to eat but how does one get those eggs off? I tried to soak in salt. Vinager and also some castle soap. This little eggs are so attached especially to the curly kale. I hate to waste all my plants. Any ideas??? It is literally every inch covered in eggs.
Aaron (Mr. DeannaCat)
Hi Sharon, guess those cabbage white butterflies have been busy! Can you brush the eggs off with a sponge or even using your hands? If you continue to treat your kale with BT the number of eggs and caterpillars will slowly diminish with time. As it gets colder the butterflies will slow down and it won’t be as much of an issue for you.
Renae Mattson
Hello! I have an aphid infection on my milkweed plants. I see in the article that this soap won’t hurt caterpillars, but I have some teeny tiny ones and want to make sure the soap is safe for 1st and 2nd instar cats. Thanks, Renae
Aaron (Mr. DeannaCat)
Hi Renae, the caterpillars will be just fine, you can rinse it the plant off afterwards with water which can knock off the dead aphids while rinsing the caterpillars as well. Just try and be as direct as you can with the spray to only spray your target (aphids). Hope that helps and good luck!
Kathie
I have Castile soap, but my husband saw a recipe that also called for orange oil. I’m reluctant as can’t find the site. Is it okay to add it to insecticidal soap or not? If so, how much should I add?
Aaron (Mr. DeannaCat)
Hi Kathie, you can add different essential oils to your pest or preventative sprays to help repel pests. Our neem oil spray does include some optional essential oil additions such as peppermint, lavender, orange, tea tree, or eucalyptus among others. 10-20 drops per gallon of spray should be a good amount to use, though I would start on the lower end to begin with. Hope that helps and good luck!
Gwen Cook
What do you recommend to kill ants on plants? I have tons of them in my garden. Especially on my artichokes.
Aaron (Mr. DeannaCat)
Hi Gwen, this soap spray recipe in the article will work on ants as well as aphids. Ants themselves aren’t always a problem, however, when it comes to ants on plants and vegetables, they are usually farming aphids so you can usually find both of them together. Good luck!
Jasmine Davids
I have lots of snails in my garden how do I deter them i dont want to kill them just for them to leave or not want to be there thanx
Aaron (Mr. DeannaCat)
Hi Jasmine, check out our article on Organic Slug & Snail Control: 10 Ways to Stop Snails or Slugs. Hopefully you can find a few ideas in there to prevent snails from getting to your garden. Good luck!
Cindy Busche
Any ideas for natural ways to get rid of Japanese beetles? They have decimated my zinnias! :{
Aaron (Mr. DeannaCat)
Hi Cindy, the most common methods are hand picking them early in the morning when they are most active or using pest sprays such as a soap spray to spray directly on the beetles or neem oil spray on the plants themselves as a preventative measure. You can also treat your soil with beneficial nematodes which will attack the beetle larva before they turn into adult beetles which should reduce your beetle population. Just be sure to select the correct nematodes that will work for Japanese beetles. We have used beneficial nematodes to combat curl grubs and it worked very well. Check out our article on How to Kill Grubs & Garden Soil Pests Organically w/ Beneficial Nematodes. Hope that helps and good luck with your zinnias, they are a beautiful flower and one of our favorites!
Hank Cowdog
Since you can brush your teeth with Dr Bronners, any tiny amount left on the plant after a washing and/or a couple of rains should not be a problem.
Shawn E
Hank, Yes on the bar soap. That’s what I use. NO on the liquid. But Dr Bronners bar soap is a wonderful tooth cleaner. No Glycerin to encourage bacteria! wonderful clean. less staining from coffee. I’ll never go back to toothpaste.
Mboo
How to get rid of caterpillars
Aaron (Mr. DeannaCat)
Hi Mboo, check out our article 8 Organic Ways to Get Rid of Cabbage Worms & Cabbage Moths, good luck!
Deb A
Love all this info!! Question about using Dr. Bonner’s – what about eating after spraying with this soap – sage, for example. Will rinsing be enough to eliminate the soap or is it absorbed by the leaves?
Aaron (Mr. DeannaCat)
Hi Deb, rinsing it afterwards should work just fine.
Tracy
Hi, I just have a slight concern over the Palm Kernel ingredient listed on the Dr Bonners soap – I can’t find any info as to its source, if it’s sustainable or not. Any ideas please?
Aaron (Mr. DeannaCat)
Hey Tracy, check out this FAQ or a press release that Dr. Bronner’s put out about it. You will have to decide if it’s something you want to support or if there are other alternatives, yet most other brands of soap ingredients include items that are hard to pronounce and I would have to look up to even know what exactly they are. Hope that helps and good luck!