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Dr. Bronner's Products

Castile Soap Spray for Garden Pests

As flattered as I am that pests find my garden delicious – after all, this is precisely my purpose in planting it – I still don’t want them there. Call me selfish, but I really want to eat my veggies myself, or feed them to my family and friends.  

Happily, the same Dr. Bronner’s Castile Soap that is designed for body washing is also, oddly enough, an eliminator of garden pests. Did you know this? 

I don’t fully understand why this is so, and a quick online search produced more possibilities than answers. However, it works! Best of all, there is nothing harmful to humans by spraying plants with a soap that is biodegradable, has no petrochemicals or synthetics, and is made from pure organic vegetable oils.  

As you’ll see in the video, you’ll need: 

  • A spray bottle  
  • 1 Tbsp. (15mL) Dr. Bronner’s Castile Soap 
  • 1 quart (1 L) water  

I recommend a food-ish scent just in case the plants absorb some of the essential oils. Peppermint, Citrus, and Unscented are all great options. If your water is particularly hard, consider using distilled or filtered so that mineral deposits don’t build up on leaves. 

Combine the soap and water in a spray bottle. Spray plants thoroughly. Be sure to spray stems, and under the leaves where bugs hide. Spray early in the morning or evening so that the heat of the day does not evaporate the spray immediately and is effective longer. You may need to spray plants daily for a while to thwart an intense infestation. 

Although my research indicated that a soap spray will not harm beneficial insects like bees and ladybugs, you can be sure not to bother any by giving the plant a quick shake before spraying.  

Rinse your produce after harvesting. You can even add a drop or two more Castile soap, which makes a great produce wash. Happy plantings! 

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Christian says:

Hi. Will this help with ants? We work in Cambodia and ants have infested our herb garden!

Lisa Bronner says:

Hi Christian- When ants appear indoors at my house, I use a stronger dilution, but it can burn plants. This lighter dilution of 1 Tbsp. in 1 quart of water is safe on plants and should do the job. If you can find the ants’ nest, try sprinkling diatomaceous earth (DE) around it. Keep in mind that ants are often indicative of another garden pest in the area, such as aphids, black scale, or mealy bugs. If that’s the case, the Castile Garden Spray will help there as well.

Ivan Magana says:

Hello Lisa ,

Im not sure if you been asked about ants but would the Castile Soap work on getting rid of them ? They are all over my Nopales and Guava tree !

Thank you !

Lisa Bronner says:

Hi Ivan- When ants appear indoors at my house, I use a stronger dilution, but it can burn plants. This lighter dilution is safe on plants and should do the job. It sounds like you’re covering a large area, in which case this can be used in a 1G multi-use sprayer with a hose attachment. Another tip is if you can find the ants’ nest, try sprinkling diatomaceous earth (DE) around it. Keep in mind that ants are often indicative of another garden pest in the area, such as aphids, black scale, or mealy bugs. If that’s the case, the Castile Garden Spray will help with this as well.

Van says:

Lisa, I heard about Dr. Bronner’s Peppermint Liquid Soap on a local radio Gardening show last month. A Lady called in and said she had been using Dr. Bronner’s Peppermint Liquid Soap mixed with water, Isopropyl Alcohol & baking soda to treat some insect problems. I grow Orchids in my greenhouse and I’m always looking for new ways to control them. I was driving my car & didn’t have a chance to make notes and wondering if you have any idea of what the mixture might be. She suggested that the baking was to help with any bacteria problems that might occur in a greenhouse. I would like to share this with our Tulsa Orchid Society.
I did find Dr. Bronner’s Peppermint Liquid Soap at my local Reasor’s grocery store, bought a bottle just to try. I was so impressed when I washed my hands with your product. My hands were so squeaky clean & a nice scent, I was sold!

Lisa Bronner says:

Hi Van- I’m glad you liked the Peppermint! I’m hesitant to comment on the addition of alcohol and baking soda as this is not something I have ever done for plants. The person who recommended it sounds like a specialty grower, and I would hate to point you in the wrong direction there. I don’t know how the baking soda would help with bacteria, but the alcohol would be more likely to do that. However, I really have no idea regarding the impact of alcohol on plants. I’m sorry not to be of more help.

Barbara says:

Will this spray deter/kill flea beetles on Eggplant leaves please?

Lisa Bronner says:

Hi Barbara- I’ve not encountered flea beetles, but I believe the Castile Soap Spray would be be effective. Keep in mind the soap needs to come in contact with the pests when it is wet.

Dawn says:

Hmmm wrote a question today, no response, do you just edit out the ones you want? If you didn’t want it public, you could have responded by email. Can’t find an answer anywhere.

Question again: Will Dr. Bonner’s soap in homemade insect spray for aphids harm the frogs living in my container vegetables?

Would really appreciate a response. June 22, 2022

Lisa Bronner says:

Hi Dawn- I apologize for my delay in responding. Yes, sadly in this day of robo-comments, I do need to approve each comment individually in order to keep the thread on-topic and meaningful. Regarding insecticidal soap and frogs, the soap on their skin probably wouldn’t be the best for them, though I’m not seeing specific research on it. I am seeing that if you touch a frog with soapy hands, it can irritate the frog’s skin. I think we can extrapolate that it would not be best to spray frogs. Frogs around my house are nocturnal – I don’t know if all are – so to avoid spraying them, try spraying plants in the morning, after the frogs have turned in.

I don’t know a whole lot about frogs, though, so please consider touching base with a nearby reptile & amphibian supply store.

Dawn says:

Apologize for being so abrupt. Thanks, this helps. They’re tiny baby tree frogs that live in my plant containers until they grow then disappear. Being so tiny, don’t want to harm them. Unfortunately, they are active during the day so will try spraying the leaves at night. Enjoy your day.

Dawn says:

Will using Dr. Bronner’s soap to kill aphids harm the small frogs living in my potted plants, I have lettuce in containers.

kozy says:

I thought I quickly read somewhere recently, but cannot find it again, that a Bronner soap pest spray has beneficial nutrients (spraying a cannabis plant I believe) … could you please verify Lisa, and list those beneficial nutrients. Thank you SO much, your family and products are all iconic and a role-model to the planet! ❤❤

Lisa Bronner says:

Thank you, Kozy! This is a new one to me, but it could be my gardening knowledge doesn’t go deep enough. I am familiar with the N-P-K (Nitrogen, Phosphorus, Potassium) needs of plants, but I can’t think of how our Castile would provide them.

I am hoping another reader will jump in here and give some insight!

Jocelyn says:

Can castile soap be used in the soil to kill or repel grubs? Would it harm plant roots?

Lisa Bronner says:

Hi Jocelyn- Fortunately (for me, but not for you) I’ve not had to treat for grubs, but my guess is that pouring soap into the soil would change the soil chemistry and harm your plants. Check with your local organic nursery for recommendations for an organic treatment.

Julie says:

I know that the usual “1 T Dr. Bronner/1 qt water” aphid spray will not kill ladybugs, but do you know if it would kill ladybug larvae?

Lisa Bronner says:

Hi Julie- No, the spray only has an impact on exoskeletons. Larvae don’t have exoskeletons yet.

Julie says:

Now I am really confused. Adult ladybugs have exoskeletons! What am I missing here? BTW, my family has used Dr. Bronner for at least 30 years. Thank you for such an amazing soap.

Lisa Bronner says:

Hi Julie – I’m so sorry for not seeing your response last month. The exoskeleton on a mature ladybug (and other larger beetles and spiders) has undergone greater sclerotization, or hardening, than the pest insects the soap spray is targeting. The exoskeletons of aphids and ants are softer, which makes the soap spray effective against them. In the ladybug’s pupal stage of development which lasts about 1-2 weeks, the exoskeleton is not fully formed and may be susceptible to the spray.

kozy says:

why do you want to kill ladybugs? they are SUPER beneficial to the garden, killing/consuming aphids, mites, larvae, etc… or is that the point?

Lisa Bronner says:

Hi Kozy – Soap sprays are effective against smaller, soft-bodied insects like aphids and whiteflies, but the larger hard-bodied arthopods like ladybugs aren’t impacted by it.

Rich says:

Do you have a list of pests this will stop?
How about leaf miners?
Thanks, I’ve been using your peppermint soap since 1971

Lisa Bronner says:

Hi Rich- Hearing from long-time customers is always a pleasure! I don’t have a list of insects, but leaf miners are larvae that live inside the leaf. Castile Soap needs to come into contact with the insect and so unfortunately, a soap spray wouldn’t be effective against these critters.

rachel elizabeth morris says:

Love the Bronners! I am just curious how this spray affects my soil. I sprayed it on my brussels sprouts and have a whiteish area now underneath all my plants. Thanks for helping!

Lisa Bronner says:

Hi Rachel- Most likely what you’re seeing is the reaction of a true soap like our Castile Soap and the minerals everpresent in the environment. Water the area to rinse away the minerals.

Prasad says:

Warm water your soap and equal part canola oil creates an emulsion. Magic

B. says:

To Prasad: I’m curious what this ‘MAGIC’ you’ve discovered is beneficial for?

And is the magic related to the canola oil working specifically for something or, is the magic simply the emulsion properties in general?

I understand the advantages and need for emulsions (for other potentially unaware readers: an emulsion allows for 2 liquids to mix that wouldn’t normally mix like oil and water … eg. adding essential oils (EO’s) to a liquid that serves as an emulsion would allow the EO’s to be mixed in with water).

Where I’m a little confused about your magic find is, normally I’d add EO’s to the Castile soap itself, of which, the soap would act as the emulsion ingredient in adding the EO’s to water …
… so I’m having a hard time gathering what substance it might be that doesn’t mix with castile soap that the canola oil would serve to be an emulsion for?

Note to Lisa: I’m skeptical the OP (Prasad) is going to see this question and reply … so it would be greatly appreciated if you could let me know if you’ve any insight into any possibilities here!

Thank you in advance to anyone who can and/or does provide insight!

Lisa Bronner says:

Hi B.- Yep, as you explained, soap is an emulsifier, which means it is able to mix two liquids that on their own would not mix. Soap is hydrophilic at one end of its molecule, meaning it is attracted to water, and hydrophobic at the other end of its molecule, meaning it is attracted to oil. It’s a pretty neat ability, and sometimes I get a little overexcited myself and call this magic. I don’t know the purpose of creating a mixture of equal parts water, soap, and oil, though. If the soap were busy holding the oil and water together, it wouldn’t be available to do anything else, like clean something or get rid of garden pests.

Sue says:

I have used Dr. B’s peppermint soap on garden pests for quite awhile & believe me, it works! Rose aphids, pests on my Meyer lemon trees, & even when I got mildew on some plants – it did the trick. I feel very comfortable spraying this solution on so many things & will continue to do so.

Lisa Bronner says:

Excellent! Thanks for sharing this, Sue!

Gary says:

Do you know how much the soap weighs in grams? I struggle with making smaller amounts of the soap spray because it is rather difficult to measure out a half tablespoon of soap and then get it into my spray bottle. It would be so helpful for making small quantities of soap spray if I could just use my kitchen scale to weigh out the soap.

Lisa Bronner says:

Hi Gary- By my measure, 1 Tbsp. of the Castile Soap weighs 15.88 grams. I’ve found a funnel or cup with a spout exceedingly helpful in mixing up dilutions.

Peter says:

Get yourself a few blunt tip syringes of different sizes. They’re very inexpensive and super handy.

Lisa Bronner says:

Peter – That is a brilliant idea! I have some of those around from dosing medicines to young children and pets. Great reuse!

Jeff says:

Does the soap harm the beneficial mychorrizae in the soil? I have carpenter ants getting in the soil of some newly planted trees. No doubt they’re attacking the worms. I think peppermint or eucalyptus soap will work best, but I’m concerned about the mychorrizae.

Lisa Bronner says:

Hi Jeff- I’ve not tried this, but my guess is that pouring soap into the soil would change the soil chemistry. Instead, try sprinkling diatomaceous earth (DE) around the ants’ nest.

Lonnie Gordon says:

I found that Dr. Bronner’s mixed with water, kills ants in the house, and removes their pheromone trail. It;s the best non-toxic spray I have found! Thanks.

Stephanie says:

Who knew?! Will this dilution work on fungus gnats for indoor plants?

Lisa Bronner says:

Hi Stephanie- Yes, the insecticidal soap will work against fungus gnats, but it does have to come into contact with them when wet. The challenge is, they are so quick to fly away at the slightest disturbance. Another reader shared that for larger plants she used a stone topdressing and for smaller plants, she had success sprinkling cinnamon on top of the potting mix. I have not tried this though. If you give it a go, let me know how it worked out.

Stephanie says:

Will this work to deter and get rid of gophers/moles in the yard too? I heard they don’t like the scent of peppermint oil and was wondering if the peppermint castile soap would be effective?

Lisa Bronner says:

Hi Stephanie- I know how frustrating gophers/moles can be! I have too many of them, too. I do not think our soap is sufficient to deter them. Because it biodegrades so quickly, generally a good thing, the critters might avoid the area for a bit, but they’ll come back. I don’t have great ideas on remedies here. The best defense I’ve had against them is a cat.

parks says:

I’ve tried everything. Smoke bombs, CO, pinch traps, poison seeds, poison worms, sound in the ground, etc. Scissor traps work. Get a good one or two that you stick in the ground over the hole and set by pushing on it with your foot. Be sure hole is active by stepping on all of the mounds the night before and see which one came back that night.

Lal says:

Fyi, Moles are a great way to control other yard pests like grubs, beetles and termites! Let them be, cheaper than grub or termite damage and chemical treatments.

Birdie says:

Sorry, I know this comment is a little late. The only way to get rid of moles, is to get rid of what they eat. Mole crickets are typically the problem, but to find out, you can mix 2 tablespoons of Castile soap in a watering can with 2 gallons of water, and go to an area of your grass where it’s browning or has dead spots and pour the mixture over a 2-3 sq ft area. This will make mole crickets come to the surface, if they are there. If you do find them, on a day where there is overcast and no direct sun, but no chance of rain, water your grass very well. When you’re finish watering each area, use a spreader to apply DE (diatomaceous earth) to your lawn, using the directions from the DE. Make sure to wear a proper dust mask when applying it, even if you have to add sand to spread it evenly.

Linda Andreasen says:

Can i spray castile soap alo g the baseboards of house? I would be trying to create a border that they will not cross. Therefore no ugh bugs in house.
To me its the perfect plan

Lisa Bronner says:

Hi Linda- A bug spray made with 1/4 c. (60 mL) of your favorite Castile soap and 1 quart (1L) of water will tackle silverfish, ants and other insects. Spray them with this solution. Do not use this concentration on plants though, as it will burn them. If possible, find their point of entry and seal it, or at least surround it with pure essential Peppermint Oil (use a Q-tip to apply it directly to their entry).

Bev says:

Does anyone know if this is safe for amphibians and lizards? I want to get rig of scale and mealybugs, but not at the cost of my frogs, toads, and lizards. I know essential oils are not good for them, but is this soap, in its baby, unscented form, safe to use in a garden teeming with amphibians and lizards?

Lisa Bronner says:

Hi Bev- I wouldn’t spray amphibians and lizards directly because it could irritate their mucous membranes (at least the amphibians), but the residues from spraying garden pests would not be harmful.

It Actually Works! Using Castile soap to get rid of household bugs. | Going Green with a Bronner Mom says:

[…] be surprised. I’ve seen it work on my garden pests, as in the previous blog on spraying for aphids and other insects. However, there’s something about ants that always makes me think they’re invincible. I […]

Lisa Bronner says:

Hi Sherri- I would think so, although I haven’t tried. Because the sturdiness of flowers varies greatly, test on one flower of that particular plant. Let me know how it goes.

Heidi says:

Hello, I was just wondering if it might help in getting rid of chiggers all over my yard. We seem to have developed an infestation this summer and now I can’t garden without getting multiple bites. I was trying to find a nontoxic spray solution I could use to spray my entire yard without harming my plants or the birds that visit.

Lisa Bronner says:

Hi Heidi- I think the soap will kill chiggers on contact if it encounters them wet. However, the residue will not have a repellent effect. A soap spray might help reduce them a bit but I don’t know that it would be a long-term solution. I think the chiggers that bored into the dirt would be unaffected.

Can other readers provide input?

emma says:

Do you have any recipes to spray on the outside perimeter of my home to keep pests from coming inside?

Lisa Bronner says:

Hi Emma- There isn’t any residual action of the soaps that would help keep pests out over time. The soap needs to contact the pests while it is wet. As much of a pain as it is, the best option is to try to find where they’re coming in and block it. I know that is not easy.

Peter Schmidtke says:

Hello– trying to eliminate pests from feasting on cantaloupe in my garden. (Not sure if they are slugs, but I believe so). Will spraying diluted Dr. Bronner’s soap DIRECTLY onto the cantaloupe help out with that? I’ve already lost one cantaloupe, trying to avoid losing more.

Lisa Bronner says:

Hi Peter- I do not think the Castile Soap will have much residual effect on repelling pests, although it won’t hurt if you want to give it a try. I also am growing cantaloupe. It is important to keep the developing melons off the ground. I slide thick cardboard squares under each one. Plastic foam board is also good. I’ve been trying the beer trick in my tomato bed where I’m having slug problems. So far I haven’t caught any though, so I don’t know if I’m doing that right. The best thing I’ve found for slugs and snails is to catch them in the act. Around here that means heading out right when it gets dark. Then I relocate them far away. Good luck! There’s nothing like a homegrown cantaloupe.

Sammi says:

Hi, I want to get rid of aphids, beetle flea looking things, and tomatoe caterpillars. I’m worried to use castille soap though I haven’t seen anything bad when I do a quick search. I’m trying to keep our garden organic and non toxic when we go to eat it and sell it. Will using the soap get into the plant chemistry?

Lisa Bronner says:

Hi Sammi- The insecticidal soap works on the insects themselves, and is not systemic to the plant. Castile Soap is made with organic oils and used as directed, the garden spray will not harm plants.

beverly says:

can you use the castile soap and water on raspberry plants for flies

Lisa Bronner says:

Hi Beverly- Soap has to be wet when it comes into contact with insects to be effective, which can make tackling flies tricky. Spray twice a day, on both sides of the leave, in the cool of the day until the infestation clears. Because flies are drawn to a source, take care to pick fruit as it ripens and remove overripe fruit.

Birgit G says:

How much of the castille soap should i use, if my source is a bar, not a liquid?

Lisa Bronner says:

Hi Brigit- To make an insecticidal soap with the Castile Bar Soap, bring one quart (1 L) of water to a boil and add ½ Tbsp. (7.5 Tbsp.) of grated soap. Mix and let cool. I haven’t tried this recipe, but it’s the equivalent of using the liquid soap. If you give it a try, let me know how it goes! Here’s my cheat sheet for using the Bar Soap in place of the Liquid Castile: https://www.lisabronner.com/bar-soap-dilutions-cheat-sheet/

Linda says:

Thank you for this information.
I hope it will ward off Beatles they are killing my roses 🌹

Craig Mackie says:

I have a small caterpillar on my Currant bush that is eating all the leaves. Would Castile Soap eliminate these little buggers?

Lisa Bronner says:

Hi Craig- I really don’t know. They don’t have exoskeletons, so I’m not sure the soap would affect them, but likely it wouldn’t hurt the plants if you want to give it a try. For slugs and snails, I’ve heard a dish of beer eliminates them. Not sure if it would work on caterpillars. If you try it, let me know!

Kelly says:

Hi Craig, I actually had to tackle multiple small caterpillars enjoying my basil plant this morning. The spray works to knock them off, but they need an extra squirt to die. Once I sprayed and they fell to the ground, I squirted them 1-2 times more and they were dead.

Mike Ryan says:

Hello Lisa. Thank you so much for the great information!
Do you think I can blend some of our peppermint leaves in the water prior to adding the castile soap?

Lisa Bronner says:

Hi Mike- That sounds lovely! There would not be a reaction with the Castile soap. Are you thinking that the natural mint oils may serve as a repellent? Let me know how it works. This blend will not be shelf stable, so make up what you will use in a couple days, or keep the mixture in the fridge for a week or so (I know that sounds odd).

Danielle says:

Excellent video! A related question – what do you do for weed control? I know you’ve mentioned that full strength all purpose spray castile will burn plants (so perhaps would kill them?), but can you use Dr. Bronner’s castile or Sal Suds for making a weed spray? I live in the mountains and have hearty weeds that I’m trying to get rid of but I don’t want to ruin the soil or surrounding plants and trees (my husband wants to use salt water, but I’ve read that that is pretty harsh to soil and surrounding plants). I’ve scoured your blog and comments, but can’t find anything on weeds… would love you thoughts!

Thanks as always!

Lisa Bronner says:

Hi Danielle- Thank you! I’m glad you enjoyed the post! For weeds, I would not use the Castile soap widely for the same reason as salt water. It could change your soil chemistry and render it difficult for growing anything. Because I am in such a dry climate where we get no rain from April to December, weeds aren’t as tenacious as elsewhere. I just clear them out by hand, pulling their roots. I realize this isn’t a solution for large areas. Let’s see what other readers have to say.

Readers, can you share ideas on good weed control?

Christin L says:

I have used white vinegar in the past—it’s great for the crabgrass on my concrete walkway–but it doesn’t discriminate, so be careful~~only spray vinegar on the weeds you want eliminated!

Iretha says:

If it’s crabgrass I hope you find something and will share! If it’s others I’ve had wonderful luck with a good dose of just boiling water. It’s amazing how it’s gotten rid of those little buggers that grow along the walkway and driveway cracks. Might need to repeat it after a few weeks but no harm to the earth! 😉

Judith says:

You can also get a stronger vinegar at the feed store (20%) or garden supply. Adding a tsp of dish soap (or Dr Bronner’s) will make the vinegar adhere to the leaves of the weed. (Some gardeners add Epsom salts (magnesium sulfate) or table salt but horticultural experts say that both of these salts harm the soil.) It’s important to apply the solution early on a SUNNY day. You may have to apply it a second time to resistant weeds and you may have some weeds grow back but it has always worked great for me.

Katy Okuyama says:

Lisa,
You were fabulous! I love the garden grounds so alive and fruitful .

Aloha and stay well
Katy

Lisa Bronner says:

Hi Katy- Great to hear from you! Thanks for your kind words! For full disclosure, this is my sister-in-law’s garden because mine wasn’t doing much at the time we were filming, but I’ll be posting some pics of my own garden on Facebook pretty soon. It’s coming alive!

Lisa Bronner says:

That’s great, Sheila! I’m glad this reached you at just the right time.

Debbie Czech says:

WOW! ! ! I did not know this! But, I will try your suggestions. I an 74 years old and live in Phoenix AZ. I usually take the summer off from planting because not everything will grow in the summer here. Right now I still have tomatoes and Pepper plants, but I am sure they won’t last much longer! I will begin planting at the end of September, and will employ your suggestions then! Thank you sooooooo much!

Lisa Bronner says:

Hi Peter- Yes! Like most animals other than humans, rodents can be deterred by mint.

Carolyn M says:

Good to know! I had a somewhat similar experience a few days ago. We had a plague of newly pupated tent worm caterpillars all over our deck. Last summer, they nearly decimated our mature trees. I grabbed a spray bottle the castile soap/water All Purpose Spray recipe and … sprayed them. It worked like magic. I happened to have just the plain castile soap in it. Simply amazing and so pleased to use something nontoxic and nonstaining.

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Lisa Bronner

Green means life. “Going Green” is living in such a way to promote vitality and vibrancy in every sphere of life. Grab an idea to make your days healthier, simpler, and more beautiful at their core.

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