How to Properly Emulsify Neem Oil & Make a Safe Garden Pest Spray
Last Updated on September 1, 2022
Neem oil can be a great, non-toxic, useful product to protect your plants from pests or disease. That is, when it is mixed and applied properly! The big issue is that oil and water don’t easily mix, and most people don’t realize how to do this. When neem oil is not fully emulsified, is used in excess, at the incorrect time, or in the wrong situation, it can actually do more harm than good!
If you are here, researching how to mix neem oil, chances are you may already be somewhat familiar with neem itself. Just in case you aren’t, let’s briefly go over what neem oil is, how it works, and what pests it fights. Then I will show how to properly emulsify concentrated neem oil in water, to create an effective and safe spray solution to use in your garden.
What is Neem Oil?
Neem oil is a plant-based concentrated oil, extracted primarily from the seeds of the India-native neem tree. The oil is then diluted and mixed with water, and applied to plant foliage as an organic pest control. Cold-pressed extractions yield the highest quality virgin neem oil, and contain all the desirable active constituents. That is what we use! Check out our favorite cold-pressed neem oil here. In addition to being a natural, mild insecticide, neem also has healing medicinal properties and is commonly used in personal care products for people.
“Neem oil is made of many components, including Omega 3, 6, and 9 Fatty Acids. Azadirachtin is the most active component as a pesticide. It reduces insects ability to feed, and acts as a general insect repellent. It also interferes with insect hormone systems, making it harder for insects to grow and lay eggs. Azadirachtin can also repel and reduce the feeding of nematodes.”
Oregon State University
“Neem oil” is sold either as concentrated 100% pure neem oil, a concentrated neem oil containing other ingredients, or pre-mixed, ready-to-use spray. Personally, we prefer to use the 100% pure stuff and mix our own. It is the most cost-effective and safe. Furthermore, one pre-mixed neem oil product line was recently found to be contaminated with several synthetic, non-organic pesticides that weren’t included on the label, including Malathion, Chlorpyrifos, and Permethrin! Yuck.
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About Neem Oil Safety
As moderate health-nuts and toxin-phobes here, we have done quite a bit of research on pure neem oil. Studies show that the only risk of acute harm to mammals or humans is if they’re exposed to very high concentrations of undiluted neem oil. Even with prolonged ingestion of high doses, the internal damage caused typically heals once the exposure is removed!
When applied correctly (follow instructions!) dilute neem oil is non-toxic and safe to use around humans, birds, pets, mammals, and most wildlife. Neem is not carcinogenic, and no chronic health effects from exposure have been found. However, neem concentrates can be slightly toxic to fish and amphibians, so extra precaution should be taken around aquatic environments.
What types of pests or diseases are neem oil effective against?
Neem oil is particularly effective against small soft-bodied insects. Examples include aphids, thrips, spider mites, mealybugs, scale, and white flies. When applied directly, the oil can coat their bodies and kill them – or otherwise interfere with reproduction and feeding. It is also said to repel mosquitoes, flies, cabbage white butterflies, and moths.
On the other hand, neem oil is not toxic to bees when used correctly! It also doesn’t bother other beneficial insects like ladybugs, earthworms, parasitic wasps, spiders, or adult butterflies – as long as they aren’t directly sprayed with it! Therefore, take care to spray it only in the evening hours, when beneficial insects are least active. Note that neem doesn’t do much to control caterpillars, except maybe repel their adult butterfly or moth form.
Additionally, that protective shine that neem oil adds to leaves makes them less susceptible to fungal diseases like powdery mildew, rust, or blight. It can help prevent fungal diseases from occurring, or slow their spreading, but is only marginally effective at treating an outbreak once established.
Using Neem Oil in the Garden
In our experience, neem oil is does a great job at preventing pest issues, and deterring pests. However, if you have a full-blown infestation of something like aphids, or a serious case of powdery mildew, we have not found neem to be very successful at bringing something back from the brink of death. Therefore, it is often recommended to apply neem oil sprays as part of a preventative care routine – for plants that you know are prone to issues. Or, start neem oil applications at the first sign of disease. Catch it early!
As a pest infestation or disease progresses, neem can still be used in conjunction with other pest control methods to bolster the effort, but may not be able to combat it on its own. Learn more ways to prevent or treat powdery mildew organically in this article, and 25 other organic methods to battle common garden pests here.
How we use neem in our garden:
In our garden, we don’t use neem oil heavily, though we do have a handful of pest-prone plants that appreciate a routine neem spray. For example, on artichokes. They’re total aphid-magnets, and also get powdery mildew very easily! Our citrus trees and passionfruit vines are commonly affected by mealybugs. Even though we also release predatory beneficial insects on those plants, an occasional neem spray helps knock the population back. Most often, we use neem on our cannabis plants, but only before they begin to flower. To read more about our cannabis pest control routine, see this post!
On the other hand, we use very little neem oil on short-lived plants in our vegetable garden. One, because as I stated: it isn’t a total problem-solver. Two, a lot of what we grow are leafy greens… I am not a fan of using neem oil on vegetation that I am going to consume, like kale, swiss chard, or lettuce. It leaves a bit of an oily residue behind that can be difficult to wash off. However, for the leaves of squash plants, tomatoes, cannabis, or other foliage we aren’t going to directly consume, it is a good product to keep in your pest control toolkit!
And now, what you came here for…
HOW TO MAKE NEEM OIL FOLIAR SPRAY
Ingredients
- One gallon of water
- 1 tablespoons of concentrated, cold-pressed neem oil
- 1 teaspoon liquid soap OR 1 teaspoon pre-wetted silica powder, explained below
- Optional: 1/8 to 1/4 teaspoon aloe vera powder (recommended for cannabis plants) and/or a few drops of essential oils
- Scale all ingredients up or down evenly as needed
Unfortunately, you can’t just mix all of these things together in your pump sprayer and go to town. Just as we all learned in elementary school science class: Oil and water don’t mix. Or at least, not easily.
Thus, it is important to fully emulsify the neem oil before adding it to the water in your sprayer. If it is not properly emulsified, it won’t mix well. The neem will come out globby and uneven on your plants. I think this is where most people go wrong with neem. Not only does this make the spray less effective, but it increases the risk of damaging the areas of the plants that get heavily dosed with undiluted neem. Strong neem can cause leaves to sunburn.
Note that even if it is fully emulsified at the time of use, neem oil will try to re-separate from the water with time. If you make a large batch and attempt to store it, ensure to shake it thoroughly and check to see that it is still nicely mixed prior to use! We usually make a fresh batch of spray each time we need it. Especially because we add aloe vera, which should be used immediately after mixing.
Emulsifying Neem Oil
This is where the soap or silica come in to play. Both act as emulsifying agents, allowing the neem to mix with water. So, should I use silica or soap? That is a personal decision.
We most often use silica (potassium silicate) to emulsify neem oil, because it provides additional benefits to the plant. For example, silica increases tolerance to stress and drought, and strengthens cell walls – which leads to larger stalks and plants. It also lightly coats the leaves, making them less susceptible to fungal diseases like powdery mildew or impacts of little leaf-sucking insects.
OR
Liquid soap can also be used to emulsify neem oil. Dilute liquid soap is a common DIY garden spray used against aphids and other soft-bodied insects, disrupting their cell membranes – effectively killing them when sprayed in direct contact. Our choice soap is Dr. Bronner’s Castile Peppermint soap. Insects are repelled by the peppermint odor! Therefore, while soap may not benefit the plant in the same way silica does, it has its own formidable pest-fighting attributes.
Last but not least, we like to add aloe vera powder to all of our foliar sprays. Again, this is mostly for neem applications to our spoiled cannabis plants. Aloe both feeds the cannabis, and boosts its immune system. However, we do use aloe vera in other ways in our garden, for all types of plants! For example, we create a fresh aloe vera solution to feed seedlings and support freshly transplanted plants. To read more about the benefits of aloe vera and ways to use it in the garden, check out this post!
Mixing Instructions
- If you choose to use neem and silica powder regularly, it is easiest to pre-mix a batch of silica powder with water and store as a liquid solution. This makes it ready-to-use and mix with neem whenever you need it. To do so, combine 35 grams of silica powder to 8 ounces of water. Mix thoroughly, and store in a cool dark place for up to a year. This is the small jar of cloudy “water” you see in the images below, which is enough for 48 one-gallon batches of neem oil spray!
- Fill your chosen pump sprayer with just under one gallon of water – about a quart shy. Depending on how many and how large of plants you’re working with, scale up or down as needed. You’ll find your groove with time. If you want to use aloe vera powder in this foliar spray, add ⅛ to ¼ teaspoon to your gallon of water now. Cap the sprayer, and shake thoroughly. This is our favorite one-gallon sprayer, and here is a smaller half-gallon option.
- Next, it is time to emulsify the neem oil. In small container, such as a half-pint jar or little beaker, combine 1 tablespoon of neem oil with either 1 teaspoon of liquid soap, or 1 teaspoon of the pre-made liquid silica solution described above. Stir thoroughly to combine. This should create a creamy thick yellow liquid.
- Fill a clean quart jar about three-quarters full with warm water. Yes, it is critical to use warm water to aid in mixing, but not hot. Now pour in your neem soap/silica solution. Cap the jar, and shake the living daylights out of it. If it is fully mixed, you won’t see oil droplets forming on the surface. Your neem oil is now emulsified! (It is a tad harder to tell when using soap since it foams.)
- Finally, pour the warm quart of neem solution in with the water that is already in your sprayer to create your final diluted mixture. Cap, and shake well to mix.
Essential Oil Additions
Just as the peppermint and neem odors are unappealing and therefore deter pests, essential oils can be used to accomplish the same thing. Essential oils are very, very concentrated – a little goes a long way! If you’d like, try adding just a few drops to the recipe above for a little extra protection. 10-20 drops or so per gallon of water is good.
Peppermint, lavender, orange, tea tree, or eucalyptus are some good examples of essential oils that act as natural insect repellents, though there are many others as well! We personally love this little mix-pack of certified organic EOs, for personal, home, and garden use.
How to Apply Neem Oil Spray
When applying neem oil spray in the garden, I usually wear long, reusable, rubber dish gloves. One, because I don’t want to get all oily – since I usually get deep in the plant and lift dripping leaves as I go. Two, some people can experience a mild dermal reaction or allergy. On the other hand, Aaron doesn’t wear gloves. Take precautions as needed.
We don’t suggest spraying neem on small seedlings, as it may burn them. I would wait until plants are at least a month or two old, and start with slightly less than one tablespoon of neem per gallon. For large mature plants, feel comfortable using the full recipe.
It is best to apply foliar sprays just after the sun goes down, for many reasons. One, beneficial insects are less likely to be present and active then. Second, this gives the spray overnight to do its work and dry a bit. Never apply neem oil in the middle of the day or during sunny conditions. Applying foliar sprays in direct sunlight can cause the wet leaves to sunburn.
Fully drench the target plant until the leaves are dripping. Give your sprayer a shake here and there to keep things mixed. Make sure to spray the undersides of leaves as well. That is where most pests and disease fester!
Frequency
The frequency of application will vary based on your situation, schedule, and the severity of the problem. Neem should not be applied more frequently than once per week, but also doesn’t have a very long-lasting residual effect.
For plants we are actively trying to protect, like our artichokes or cannabis plants (pre-flower only), we spray those weekly or every other week for best results. This same frequency would be good for a plant showing early signs of a pest infestation or disease. On the other hand, our citrus trees are lucky to get a spray once every month or so.
And that is how you properly emulsify, mix, and apply concentrated neem oil.
I hope you found the information in this post useful in your quest for organic pest control. If so, please leave a comment or pass it along to your friends!
May your garden stay healthy, lush, and productive. Remember, an organic garden shouldn’t be free of all insects and pests! That just isn’t natural.
If you enjoyed this article, you may also want to check out:
- Organic Pest Control, Part 1: How to Prevent Pests in the Garden
- Organic Pest Control, Part 2: How to Identify the Top 18 Pests and Beneficial Insects
- Top 23 Plants for Pollinators: Attract Bees, Butterflies, & Hummingbirds!
- Organic Cannabis Pest Control: How to Keep the Bugs Off Your Nugs
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.
205 Comments
NICOLE NOVAK
Hi Aaron! Well, I have always had a bit of a problem with white fly, but this summer it’s off the charts. I had purchased the silica per your recipe but had never had to use it until now!!!! I came home from Memorial Day weekend to the worst infestation I’ve ever seen. I have now seen THE CLOUD of whiteflies. I knew I had some on my strawberries and a couple of pepper plants, but now they are on EVERYTHING. I made up your solution, following the instructions to the letter and had to make up 6 gallons for just this one application. I would like to spray every 3 days instead of once a week so I can get this under control. Is that ok?
Aaron (Mr. DeannaCat)
Hi Nicole, hope all is well aside from the crazy whitefly problem, we have seen quite a few of them around our neck of the woods as well. Spraying every three days should be just fine as long as you fully emulsify the neem oil, we find that using silica strengthens the cell walls of plants and makes them more resilient to pests and disease. Good luck on getting that infestation under control!
ANTHONY LEO
I have read your article for using Neem oil as it applies to plants. My problem is grubs in my lawn. I got connected to Neem oil to use as an insecticide in the Spring. I mix the oil with water in a sprayer, but have not done the emulsifier step. My questions are application of the spray and how it actually penetrates the soil to kill the grubs before they do much damage. Does the spray penetrate the surface, if so, how deep does the oil penetrate? When emulsified, does the oil penetrate the surface? Will a rain before or after application neutralize the spray? I started using the spray last year and resumes this April. I am starting to see some damage.
Your info on your website is great, I just need to understand how the oil affects my situation. Thanks so much.
Aaron (Mr. DeannaCat)
Hi Anthony, we mostly use neem oil foliar spray on the plants themselves. If you want to get rid of grubs in your soil, check out this article: How to Kill Grubs & Garden Soil Pests Organically w/ Beneficial Nematodes. This should get you well on your way and only takes a couple treatments per year to make a big difference. Hope that helps and good luck!
Amy
Great article! Thank you for the information but I do have two questions.
1. Could I use both dish soap and silica powder to emulsify? I ask since it was mentioned that the dish soap disrupts insect cell membranes but the silica strengthens plant cell walls. Seems the both have desirable properties.
2. When using essential oils, are there any that should specifically be avoided? I know you said there were many other you didn’t list that could be used, but I wanted to make sure there were none that should not be used. I love citronella and lemongrass but if the bugs love them too, then it probably wouldn’t be good for me to use them in my garden. 😬
Aaron (Mr. DeannaCat)
Hi Amy, oftentimes we will use both silica and soap together for the reasons you mentioned. As far as the essential oils go, we don’t do anything too fancy but you could probably use citronella and or lemongrass with no issues. We actually use both of these oils in our Bug Off Balm and it helps keep the bugs away. Good luck!
Elisa
Thank you for the great article/tutorial! I received a potted calamondin plant recently and read articles that calamondin plants should be treated every so often with insecticidal soap sprays. So I would like to use your recipe using Dr.Bronner’s+Neem oil+ water. Is there a benefit to using Dr. B’s lavender or eucalyptus castile soap or is peppermint the best to use? How often would I use this spray on the calamondin leaves? I think you mentioned ust once a month? Can I also spray the soil or water the soil with this mixture to ensure there are no unwanted pests or eggs hiding in there?
I found a few mealybugs on a new large pothos plant I received with the calamondin. From my understanding of your protocol, I should thoroughly spray this solution just once a week until no bugs a found? Again, can since mealy bugs were found, csn I also use this to water the soil to kill any eggs or mealies in hiding? After solution dries up should the leaves be rinsed off in between treatments (and before regular watering)? Sorry for so many questions- I’m fairly new with caring for plants!
Aaron (Mr. DeannaCat)
Hi Elisa, a weekly neem oil spray should be enough as a preventative measure. If you see a heavy infestation on your plants you can spray every 3 days, if you only found a couple mealybugs I wouldn’t be too worried about it and once a weak treatment should be enough to get them under control. There is also no need to wash or rinse the leaves after apply the neem oil foliar if it has been emulsified correctly. You can really use any Dr. Bronner’s that you want, we like to use a scented one that usually deters pests so peppermint or eucalyptus work in that regard. However, neem oil is the main star in this foliar spray. Hope that helps and good luck with your plants.
Elisa
Thank you very much!
Seth
Any thoughts on what type of water to use in terms of longevity? Should I use distilled water so that my spray may last longer? Thanks in advance!
Aaron (Mr. DeannaCat)
Hello Seth, we typically just use water out of the tap but have also used rainwater on non edible plants or on plants before they formed edible fruit. It is best to make the spray by the batch as needed as it doesn’t store well nor is it recommended for storage. Good luck!
Tom
I’ve read that some people spray neem oil emulsion on garden soil, as a broadcast, before planting, claiming that it destroys harmful organisms that live in soil, such as the bacteria that causes wilt in cucumbers. Do you have an opinion on that?
Also, do you know the shelf life of pure neem oil? I have some that’s 2 – 3 years old and was stored in a closed plastic container, which has shriveled a bit, probably because of evaporation through the plastic.
Thanks very much for taking time from your busy schedule. Your info on Neem is the most I’ve seen.
Tom
Aaron (Mr. DeannaCat)
Hello Tom, we typically only use neem oil via foliar spray although we do amend our soil twice a year with neem meal. Using neem oil as a soil drench works as a systemic pesticide, meaning your plants or trees will soak up the neem oil and protect it from the inside out. Once neem oil is opened it is recommended to use with a year or two so it is probably best if you invest in a new bottle. Hope that helps and good luck, reach out if you have any other questions.
Jono S
Hi, this is a great guide! I’ve had good success with neem and would love to try out silica powder, as it seems like it has lots of benefits for plant use, and I prefer the idea of using this instead of soap.
I’m finding it really hard to find any in the UK though. There seem to be lots of variants of ‘silica poweder’. Is Potassium Silicate the only correct chemical for this?
I can find lots of Silica Dioxide available, but the only results for Potassium Silicate are existing liquid product – and I’m sure the liquid ones might work, but would have no idea about the correct ratios for mixing!
Thanks for any help!
Aaron (Mr. DeannaCat)
Hi Jono, you have probably seen the pre mixed potassium silicate solutions like Dyna-Gro’s Pro-Tekt? If so, those will work just fine. I believe our recipe for the silica solution is on par to the same strength as Pro-Tekt so just use about 1 tsp. per 1 Tbsp. neem oil per gallon of water. Hope that helps and good luck!
Jessi
Hello, thank you for this.
I bought neem oil that is thick and brown, and just… will NOT emulsify. Am I doing something wrong or is the neem oil off?
Thank you!
Aaron (Mr. DeannaCat)
Hello Jessi, neem oil can vary by brand but the color is usually somewhat brown. It will become less thick the warmer the temperature is in your house. Set the bottle in a bowl of warm water to help thin it out some. If you are still having a tough time, use warm water when emulsifying and add additional small amounts of soap until it emulsifies fully. Hope that helps and good luck!
Dan
I heard that soaking 1/4 cup of soap nuts in 5 gallons of water is a good emulsifier and its full of saponins which can be used alone without neem as a natural pesticide. Just wondering what your take is on this Thanks Dan
Aaron (Mr. DeannaCat)
Hello Dan, soap nuts work great as an emulsifier as they have an incredibly high amount of saponins and will work for pest prevention on their own. However, I would use them in conjunction with neem oil to create an even greater foliar spray for pest prevention. Good luck!
Jessica Bratt
Hello Mr. Deannacat,
Thank you so much for this very informative article about natural pest control. I’m slowly switching my garden to a more organic approach, so I’m doing a lot of research and this article has been one of the most comprehensive and scientific I’ve come across. I always want to know the “why” of a thing, and you’ve answered several of my “whys”.
Regarding your foliar spray recipe, would there be a benefit to using the silica AND castile soap? It seems they both hold benefits in pest reduction and health of the plants, as well as their role as emulsifiers.
If feasible, what proportions would you suggest and if not, why not?
Thanks again!
Aaron (Mr. DeannaCat)
Hi Jessica, glad to hear that the article was so informative for you. You can definitely add castile soap even if using silica and it is something that I do on occasion as well. I find it especially useful if I can’t get the oil to emulsify fully with the amount of silica that I first added, sometimes it’s easier to add a squirt of soap with the mixture instead of adding more silica. As far as amounts go, you can be fairly liberal with the amount of soap but you probably don’t need to add more than a tablespoon per gallon, even if you are going for an extra soapy spray. Hope that helps and good luck!
Tk
Hi! thank you very much for the info….Please can emulsfied neem oil that is dissolve in water last for a long time..i.e is there any ready made neem pesticide for direct use ?
Aaron (Mr. DeannaCat)
Hi TK, I believe there are some ready made neem sprays that are sold in garden centers although their effectiveness will not be close to making your own by the batch. When you make your own, it is recommended to use it immediately and only make as much as you will use for that foliar spray. Good luck!
pb
Hello, thanks for the detailed explanation for the spray. Will it be ok to apply directly to indoor plant leaves instead as I don’t have sprayer and only has a few pots. Thanks for your help!
Aaron (Mr. DeannaCat)
Hi pb, that should work out just fine. It works best when it is applied in a fine mist as the plants can usually absorb it best this way. I would still emulsify the neem as described (scale down if you want a smaller amount of liquid) and apply the liquid with a paint brush, sponge, or towel. Hope that helps and good luck!