The Downsides of Using Neem Oil for Pest Control

Are You Ready to Start Growing Yourself?

If you're ready to start growing and want to find out the best seedbanks that ship to the U.S. click here.

Neem oil is arguably one of the most popular pesticides and fungicides especially among home growers. It is organic, cheap, and effective against a number of pests and diseases. However, it is not the “miracle spray” everyone thinks it is. Like all things, neem oil also has its disadvantages and there are certain cases where it is better to use alternatives like jojoba oil. Here are a few issues that you should be aware of when using neem oil on your plants.

Miekks, CC0, via Wikimedia Commons

Neem oil can be slightly toxic

Neem oil is frequently described as having “low toxicity” and is therefore safe to humans, even by the EPA. This just means that its toxicity is within the allowable threshold, but it is still toxic. In fact, there are studies on mice that show how toxic it is and there’s even a documented case of neem oil poisoning in an adult human male and female. There have also been reported child deaths resulting from the ingestion of neem oil.

There is also a product called Naturally Neem which has a warning on its label that says it may affect the reproductive systems of terrestrial vertebrates. Other neem-based pesticides also have on their labels a warning not to expose pets to their product. Furthermore, neem oil can irritate the eyes and skin.

It may contain Azadirachtin

Neem or neem oil is typically used as a blanket term for the extract derived from Azadirachta indica or neem tree, which is also where the compound azadirachtin comes from. Azadirachtin is typically what makes neem oil an effective pesticide since it can affect a wide range of insects by acting as an anti-feedant, disrupting growth and molting, repelling and sterilizing larvae and adults, and deterring egg laying. However, Azadirachtin is also what makes most neem pesticide products toxic, in addition to other compounds neem pesticides may contain such as nimbin, nimbinin, nimbidin, nimbidol, picrin, and sialin.

It may kill other beneficial insects

As previously mentioned, neem oil with or without Azadirachtin can kill a wide range of insects. As an oil, it smothers insects by covering their breathing holes, suffocating them. Neem oil can also mess with an insect’s hormonal balance, preventing it from reproducing. However, the pest needs to ingest neem by eating the leaves that are drenched in or contain neem oil. For the leaves to contain neem, it has to be applied via soil drench, which is unsuitable for marijuana plants. 

Neem doesn’t discriminate between pests and beneficial insects and some of the common beneficial insects that it affects butterflies, ladybugs, and parasitic wasps. At concentrated doses, it can also kill bees which are critical for keeping local ecosystems healthy.

It is banned in some countries

To clarify, the laws concerning neem oil and Azadirachtin are very muddy in some countries like the UK and Canada. In the UK, some Azadirachtin-based pesticides are not allowed but it is still possible to get hold of. In Canada, neem oil and Azadirachtin is not allowed to be used as pesticides due to possible misuse. Nevertheless, the reasons behind these bans are not unfounded since it has been proven that neem oil and Azadirachtin can cause harm if used improperly. 

Jojoba oil as an alternative to neem

This video summarizes some of the benefits of jojoba oil vs neem.

Where to get jojoba oil?

Check out Protector Jojoba Oil Concentrate. It’s specifically formulated for plants and a great alternative to neem oil.

Frequently Asked Questions on Neem Oil

Is neem oil toxic?

Neem oil with Azadirachtin is slightly toxic to fish and other aquatic creatures and some studies have shown it to be poisonous to humans at high doses. It has been observed to cause metabolic acidosis, seizures, kidney failure, encephalopathy and severe brain ischemia in children.

Is neem oil and Azadirachtin the same?

No. Neem oil may contain Azadirachtin, an active component in some pesticides, but it can be processed into clarified hydrophobic extract of neem oil which does not contain Azadirachtin.

Will neem oil kill beneficial insects?

When sprayed directly, neem oil can smother most insects including beneficial ones. High doses may also harm bees. Therefore, it is best to use neem when beneficial insects are not active, or use an alternative pesticide.

What is a good alternative to neem oil?

Neem oil can typically be substituted by a combination of natural pesticides and fungicides. Jojoba oil can be used as a pesticide since it can also smother destructive insects and mites and it can be used in combination with anti-mildew solutions like potassium bicarbonate/baking soda with liquid soap.


Neem oil is still one of the most effective “organic” pesticides that can also get rid of powdery mildew –  one of the worst problems for a marijuana grower. However, it does pose a small health risk to humans, animals and beneficial insects, especially if used incorrectly. Although it can be used without much problem on ornamental plants, it can render marijuana unsuitable for consumption if used at the wrong time and sprayed on the wrong part. Expert growers may be able to use neem oil pesticides well but it may be good for novices to stick with homemade pesticides like jojoba oil and insecticidal soaps. Jojoba oil in particular is considered safe, it is a typical ingredient in a lot of skincare products and there’s no specific kind that you need to buy for horticultural purposes.

Thinking About Growing Your Own?

Check out this post where I go into the details about equipment, seeds and the reasons why I got started in this journey.

Leave a Comment