How to Use Neem Oil on Houseplants (10 Pests That Hate It!)
Neem oil has become rapidly popular amongst plant owners and can be seen almost everywhere. While it is an effective pesticide, it only works if you use it properly—I got you though! Here’s a detailed guide on how to use neem oil on houseplants and the most common mistakes you should avoid.
Neem oil is an effective natural pesticide used on houseplants by foliar sprays or soil drenching. The most common pests repelled and killed by neem oil are 1) ants, 2) aphids, 3) caterpillars, 4) fungus gnats, 5) Japanese beetles, 6) scales, 7) spider mites, 8) termites, 9) thrips, and 10) ladybugs.
Although neem oil has been used for centuries in India for a wide variety of things, the idea of using it on plants has only recently started to take off in North America. To help you catch up on a few hundred years of research, here’s how to use neem oil properly!
We actually bought the neem oil and tested it for you on our plants so you can see with your own eyes!
1. Neem Oil Foliar Spray
Combine 20 drops of neem oil and 10 drops of dishwashing liquid with 300ml of water to create a neem oil solution. Use this mixture to spray houseplants to prevent pests and treat active infestations.
Let’s find out how to correctly make and use this spray to protect our lovely houseplants!
1. Mix Neem Oil and Water
This is great when you don’t wish to use an entire gallon of water to treat only a few houseplants. You can always make more, but I’ve found that this 300ml spray bottle works well for small plants and reduces potential waste.
You can always use less neem oil, but just keep in mind that it may not be as effective.
When you first pour the yellow or brown neem oil into the liquid, don’t be afraid if it just sits at the top. Remember that oil and water never mix, so this is completely normal.
The neem oil should have a strong earthy smell. This is also nothing to be concerned about, as neem oil is generally quite pungent.
As far as I know, there is no such thing as a non-smelly neem oil—which can be a drawback. But don’t worry, the smell doesn’t linger!
2. Add Dishwashing Liquid
After pouring the neem oil, be sure to add some dishwashing liquid. You want to use the purest dishwashing liquid you can find, without any additional chemicals or fragrances.
The dishwashing liquid allows the neem oil to mix with the water. Do this by shaking the mixture vigorously until you create a milky white solution.
3. Test the Potency
But before you start using it on all your plants, test out the solution on a single leaf.
Dilute the solution or avoid using neem oil on the plant entirely if it burns or shows any reactions after 6 hours.
4. Spray on Plants
Once you’re certain your plants can tolerate the neem oil, shake the mixture again. Then, thoroughly spray the upper and underside of the leaves in side-to-side motions for even application.
Doing so will discourage pests from eating your houseplant while eliminating live insects. I use this solution on my newest plants to prevent them from spreading pests that are not easily seen by the naked eye to my other plants.
After spraying, keep your plants away from direct sunlight in a room with good ventilation to ensure the smell goes away. My plants normally become odor-free after the solution has completely dried.
This method is not only great used as a preventative measure, but it is also an easy and effective way to treat ongoing pest attacks!
2. Neem Oil Soil Drench
The soil of houseplants can also be drenched with neem oil. For this method, mix 3 tablespoons of neem oil and 5 drops of dishwashing liquid in 1 gallon of water. Pour the mixture directly into the soil to saturate the roots to control and prevent pests.
It is possible to drench the soil of your houseplants to protect them against insects and allow them to absorb the pest-repellent compounds.
However, a compound called azadirachtin in neem oil could potentially kill helpful microbes in the soil. This may not be so bad in an outdoor garden, but it can be pretty bad for our potted houseplants with limited soil and nutrients.
If a soil drench must be used, you’ll need to top-dress the soil with compost to allow the microbes to repopulate.
Why is More Water Needed for Soil Drenching?
Since we intend to drench the soil, you’ll need a lot more water than I mentioned in the first method. The dishwashing liquid will help the oil emulsify and will not harm the plant roots.
Pro Tip: To make the neem oil solution easier to mix, make it in a sealable container that you can close and shake, like a plastic bottle.
Once again, you should end up with a milky white solution.
How Do You Properly Soil Drench Houseplants?
Pour the mixture directly into the soil to saturate the roots.
After drenching the soil, keep the plant from direct sun to ensure the roots don’t burn. Use your favorite compost and place it on top of the soil to help replace any lost microbes.
This neem oil treatment should eliminate any pests living in the soil and is excellent for handling bugs like fungus gnats!
However, if you plan to use neem oil as a systemic pesticide, you should know that this depends greatly on the soil that you have. To understand this, let’s go over neem oil first.
What Is Neem Oil?
Neem oil is a natural pest repellent and pesticide extracted from neem seeds containing chemicals like azadirachtin. Azadirachtin will not directly kill pests but can cause pests to die by preventing them from feeding, mating, and maturing. Neem oil can also prevent powdery mildew.
Neem oil is one of the most highly useful products the neem tree can offer for plants. The oil is extracted from neem seeds, and similar to olive oil, the oil is cold-pressed.
This heatless method of extracting oil helps preserve the main active ingredient in neem, azadirachtin and ensures it does not get lost in the process
As you may have expected, the oil contains numerous compounds. But what’s surprising is that scientists cannot find any insect-killing agents in the oil!
Rather than outright kill insects, the azadirachtin and other complex chemicals in neem oil work by altering the insect’s behavior and negatively impacting its ability to feed, mate, or mature, until the insect eventually dies.
Additionally, neem oil can prevent powdery mildew, a common cause for white zucchini leaves. The smell of neem is also quite potent and can act as a repellent that multiple pests find unattractive, but only if you use it right.
4 Common Mistakes in Using Neem Oil
The 4 common mistakes that people make when using neem oil are 1) expecting immediate results, 2) spraying the plants immediately, 3) believing the plants will always absorb neem oil, and 4) using neem oil that isn’t cold-pressed.
It’s pretty easy to use neem oil. Just mix up the neem oil solutions and use it for your plants. So are there really any mistakes that can be made? As it turns out, yes!
But these mistakes are completely understandable, so don’t feel bad if you end up making any of them. To help you prevent making them though, you need to familiarize yourself with the 4 most common mistakes in using neem oil.
1. Expecting Immediate Results
The number one mistake I see so many gardeners make is expecting to see results immediately.
When you’re currently facing an active bug infestation, don’t expect to see changes overnight.
It might be possible for pests to start rapidly dying, but you shouldn’t use neem oil with the expectation that it will instantaneously solve your problem!
Yes, it might feel like forever when your plant is in the middle of an infestation. But remember that it takes at least a few days for the azadirachtin to take effect.
2. Spraying Immediately
After making your neem oil solution, it’s always a good practice to test it on just one leaf first. This is done to ensure that it won’t cause any adverse reactions to your houseplants.
It can be exciting to try out a new method, but don’t let this stop you from testing it out! Using neem oil without testing it first could lead to the foliage burning.
3. Believing Plants Will Always Absorb Neem Oil
If you’re using neem oil as a systemic pesticide, the plant may not take in any of the neem oil. Alkaline soils above 7 pH are not able to absorb neem oil as much.
Some plants aren’t even able to absorb the azadirachtin at all!
Additionally, neem oil can’t be absorbed through the leaves, as the neem oil molecules are usually too large to enter the stomata. The reason why it’s used as a foliar spray is mainly to kill insects on direct contact.
4. Using Neem Oil That is Not Cold-Pressed
Just because the product says it contains neem oil, does not always mean it will be effective.
Cold-pressed neem oil is essentially the only kind of neem oil that retains its pest-repelling abilities.
If the oil is extracted any other way, the azadirachtin will be destroyed, and the neem oil will not be able to control any insects.
While you can use other types of neem oil, keep in mind that it will not contain active azadirachtin, and therefore will not be very effective against insects. But after reading this, you’ll hopefully be using the right type of neem oil to repel the following pests.
10 Pests Affected by Neem Oil
Home and indoor gardeners can use neem oil to repel and kill 1) ants, 2) aphids, 3) caterpillars, 4) fungus gnats, 5) Japanese beetles, 6) scales, 7) spider mites, 8) termites, 9) thrips, and 10) ladybugs.
Neem oil can affect around 200 different life forms, so you can see how powerful this ingredient is in the garden. Here are some of the most common pests that neem oil will impact.
1. Ants
Neem oil can help repel and eliminate fire ants, black ants, and red ants with its potent aroma and active compounds. Spray the ants directly with neem oil to deter feeding.
Very few of us enjoy seeing ants in our homes and gardens. Thankfully, though, you can use neem oil to control them.
Studies have revealed that neem oil combined with garlic extract can kill black ants and stop red ants from feeding.
Fire ant mounds can also be eliminated with the use of neem oil. But other than dumping neem oil down their nest, the best way to control ant population is by spraying them directly. This will allow the azadirachtin to take effect.
I also found neem oil to be useful in repelling and preventing ants from nesting in the bottom of pots.
Check out the 14 Plants That Repel Ants to find more natural ways to deter ants!
After spraying the bottom of the pot with neem oil, I received little to no ant visitors for the following week.
2. Aphids
Aphids can be eliminated and are less likely to feed on plants treated with neem oil. Hose the aphids off the plant and treat it with a neem oil spray to suffocate the remaining aphids.
Neem oil has a strong, sulfurous odor that can discourage aphids from feeding. But for the neem oil to be effective, it must be used correctly.
A foliar spray is the best way to handle aphids. You might be tempted to use neem as a systemic pesticide and feed your plants neem oil, but this won’t have much effect on aphids.
Because aphids tend to feed on the outer layer of the plant’s sap vessels, their mouthparts won’t penetrate deep enough to ingest any azadirachtin that has been absorbed internally.
Having trouble with aphids? Learn the 3 Ways Aphids Get Indoors.
For large infestations, combine the use of neem oil with physical removal. Knock or hose the aphids off the plant and spray the foliage with neem oil afterward to help eliminate any remaining eggs or mature aphids.
The neem oil will help suffocate the aphids, and the azadirachtin will disrupt their feeding habits.
3. Caterpillars
Caterpillars like tobacco hornworms and cabbage loopers will have their growth and feeding habits disrupted by neem oil sprays. A soil drench with neem oil can also kill caterpillars in the soil.
To eliminate and discourage caterpillars, you can spray them directly with neem oil to disturb their feeding habits. Unable to eat, the caterpillar will eventually die.
Neem oil can take a few days to work though, so I suggest plucking off any visible caterpillars. Then, spray the plant down to kill any eggs and discourage other caterpillars from feasting on your plants.
Neem oil works especially well against tobacco hornworms and cabbage loopers, some of the worst pests you can find on tomato plants.
Learn more about the 25 Common Pests For Tomato Plants.
Another great way to prevent caterpillar infestations ahead of time is to water the plants with a neem oil mixture. Over time, the plant will eventually take in the azadirachtin and retain it in its leaves, discouraging hungry pests from eating it.
This method will also kill any ground-dwelling larvae and caterpillars, another big advantage!
4. Fungus Gnats
Neem oil can be used to prevent fungus gnats from infesting plants. Drench the soil with a neem oil mixture or spray the top layer of soil to suffocate the larvae and repel mature fungus gnats.
Fungus gnats are some of the most irritating pests you can face. They aren’t harmful to you, but their larvae will breed in damp soil, feed on plant roots, slowly killing them in the process.
Drench the soil with neem when you water the plant or spray the top layer of soil with neem oil.
Fungus gnats typically invade plants that are overwatered, however, so be careful! This additional moisture can worsen the issue.
To avoid harming the plant further, ensure the soil is fully dry before watering it or spraying it with neem. Do this for active infestations to suffocate the larvae and prevent mature fungus gnats from breeding in the soil.
Learn the 6 Easy Ways to Get Rid of Fungus Gnats.
5. Japanese Beetles
Japanese beetles find neem oil highly unattractive and will sooner die than eat plants with it. To deter Japanese beetles, spray the plants or drench the soil with neem oil to disrupt the growth of Japanese beetle larvae and reduce their numbers.
Aside from azadirachtin, neem oil also contains another compound known as salannin, which has proven to be a strong feeding deterrent against many pests, including Japanese beetles.
Experiments have shown that soybeans and soybean leaves treated with neem oil were left untouched by Japanese beetles for up to 14 days. Many Japanese beetles in the experiment chose to die rather than eat the neem-treated plant tissue.
You can use neem oil to treat your plants ahead of time and prevent Japanese beetles from attacking them.
For active infestations, try to drench the soil with neem oil to target their soil-dwelling larvae and lower their chances of maturing.
6. Scales
Scales are repelled by the odor of neem oil and will not attack plants watered or sprayed with neem oil. Use neem oil to physically remove scales off the infected plant and prevent them from returning.
Not all scales are bad. Some scales will do little to no damage to plants, while other species can cause serious damage to their host plants by sucking out their sap.
It’s better to be safe than sorry though. Plus, scales aren’t exactly the prettiest thing to see!
Remove the scale with a toothbrush or cotton swab with neem oil and spray the leaves with neem oil to help control the scales.
If you constantly struggle with scales, consider watering your plants with neem oil to prevent scales from attacking their azadirachtin-containing plant tissue.
7. Spider Mites
The azadirachtin in neem oil deters female spider mites from laying eggs and can lower spider mite populations by more than 50%. Neem oil can be used as a preventative measure or sprayed on infected foliage to eliminate spider mites.
From cacti to food plants, and even houseplants, spider mites seem to attack almost everything. Luckily, though, neem oil can combat them!
Research has shown that neem oil can impact the female spider mite’s ability to lay eggs and can reduce their overall numbers by over 50%.
Due to how difficult it is to detect spider mites, you can also spray plants with neem oil, as I did, as a preventative measure.
If you ever have an active infestation of spider mites (although I hope you never do), you can use neem oil to help you control it.
Hose the infected plants and spray both the upper and underside of the foliage to repel the larvae and adults and stop them from laying more eggs.
8. Termites
Neem oil is highly effective against termites. Use neem oil to treat raised beds and young trees to repel and poison termites.
As you can tell, neem oil is useful in repelling and controlling various insects. Termites, however, seem to be the most affected by neem oil.
While termites usually only feed on dead plant matter, they occasionally attack live plants. The wood of the neem tree is rarely attacked by termites, due to the presence of azadirachtin.
Not only will the smell of neem oil repel them, but it will also poison any desperate termite that chooses to ingest it!
Spray neem oil on woody plants. You can also use it to treat raised beds in the garden to prevent termite infestations.
For more natural but effective deterrents, check out the 13 Plants That Repel Termites!
9. Thrips
Neem oil can effectively kill adult and immature thrips. Infested plants can be sprayed or drenched with neem oil to protect them against thrips. To prevent the thrips from building resistance, use neem oil with physical removal or other herbicides.
Sprayed directly with neem oil, the respiratory openings on adult thrips will get clogged, and the thrips will slowly suffocate.
Drenching the soil with neem is also extremely effective in eradicating any larvae in the soil.
As tempting as it might be, however, it’s best to avoid using neem oil regularly against thrips. Over time, the surviving thrips and larvae could potentially build a resistance against the azadirachtin and create new generations of neem-resistant thrips.
Sometimes it is best to use a wide variety of pesticides to ensure pests do not build an immunity to them, so be sure to use different methods other than neem oil from time to time.
Learn more in the 6 Effective Ways to Get Rid of Thrips.
10. Ladybugs
Neem oil can kill ladybugs when sprayed directly with neem oil due to suffocation. However, ladybugs are beneficial and can help consume other insect pests, so it is best to avoid repelling and eliminating them.
This bug isn’t typically a pest, but you might need to control them from time to time.
Ladybugs normally do not eat plants, so you’ll have to spray them directly to reduce their numbers. The neem oil will cling to their bodies and make it difficult for them to breathe.
Since their diet, however, mainly consists of other insects, like aphids, it’s usually best to leave ladybugs alone.
But if they’re becoming too much or if they’re eating helpful insects, like assassin bug eggs, you can use neem oil in small amounts to help keep ladybugs under control.
FAQs
Does neem oil burn plants?
Neem oil itself is not directly harmful to plants, but if it is left on leaves and given direct sun exposure, foliage can burn as a result. Keep the plants in the shade after application and spray them with neem oil only during sundown to prevent leaf burn.
Is neem oil safe for pets and children?
Neem oil is non-toxic for humans and animals such as cats, dogs, rabbits, and birds in low amounts. Conversely, high consumption of neem oil can cause liver damage. The oil can also cause minor irritation to human and animal skin and must be washed off.
Summary of Using Neem Oil on Houseplants
Neem oil is a naturally occurring pesticide that is extracted from the seeds of neem trees. Houseplants are commonly treated with neem oil either through direct foliar spray or drench the soil with neem oil.
Ensure the best results by not immediately spraying neem oil on plants without testing, not expecting immediate results, and using neem oil that is not cold-pressed. Moreover, some plants can’t absorb neem oil.
The 10 most common pests that neem oil can control are ants, aphids, caterpillars, fungus gnats, Japanese beetles, scales, spider mites, termites, thrips, and ladybugs.
Sources
- “Neem: A Tree for Solving Global Problems” by National Research Council in National Research Council
- “A brief study on neem (Azarrdirachta indica A.) and its application-A review” by Asha Roshan and Navneet Kumar Verma in Kailash Institute of Pharmacy and Management
- “Processing Edible Oils” by Russell Schaufler and Douglas Schaufler in Penn State College of Agricultural Sciences
- “Insect Control: Horticultural Oils – 5.569” by W.S. Cranshaw and B. Baxendale in Colorado State University
- “Pesticide Profile: Horticultural Oil” by Miri Talabac in University of Maryland
