Organic Pesticides for Cannabis: Neem Oil

Neem oil is an organic product used to prevent and eliminate bugs and fungi and it’s widely used on all types of plants.
Author Enzo Schillaci
08 July 2020
7 min read
Organic Pesticides for Cannabis: Neem Oil

Contents:

Neem oil is one of the most used organic pest control products out there because it can not only prevent but also eliminate a wide variety of bugs and pests while not affecting beneficial insects that are friendly to your plants.

This organic pesticide is used in almost all crops, not only cannabis and even though it doesn’t affect the bugs directly, it prevents them from feeding and laying eggs, forcing them to look for other plants to feed from.

1. What is Neem oil made from?

Neem oil comes from the Azadirachta indica tree, commonly found in India, South Asia, and introduced to lots of other subtropical and tropical countries for its importance in organic farming and medicine.

 

Organic pesticides for cannabis: Neem tree

The Azadirachta indica tree was originally found in India but has been introduced into other countries with a similar climate due to its several uses.
 

Not only is it used in plants, but Neem oil is also good for the skin in the treatment of several diseases, used as anti-bacterial, anti-fungal, but remember you shouldn’t use it unless your doctor recommends it because there have been reports of Neem oil poisoning1 in adults and children, so be careful.

When a Neem tree flowers they produce not only small white flowers but also a small green or yellowish fruit that resembles an olive, these fruits (and the seeds) are where Neem oil is extracted from.

 

Organic pesticides for cannabis: Neem oil is made mainly from the fruits and seeds of the neem tree

Neem oil can be made from every part of the neem tree but the fruits and seeds have the most amount of it.
 

By grinding and pressing the fruits and seeds, manufacturers can obtain the purest form of this oil, although it can also be extracted with solvents it will diminish the quality.

2. How to use Neem oil

Before using your preferred mix of Neem oil, you should always test it on one leaf and wait for 24hrs to see how your plants react to it after you know it is safe to use it, you need a sprayer to completely coat your plant, including the branches and underside of the leaves so the bugs don’t have a spot to run away from it.

Here are a couple of recipes that aren't too strong, you can always increase the amount of Neem oil you mix but these ones are quite light and won't have a bad effect on your plant.

 

StageRecipe
Seedling stage8ml per 1L of water
Vegetative Stage16ml per 1L of water
Flowering Stage

Neem oil alternatives

5ml of baking soda per 1L of water

or 

500 ml of 70% alcohol with 500ml of water

How to mix Neem oil for cannabis plants.
 

Have in mind that Neem oil indeed can be used in the flowering stage but only on the stems and branches, but bugs will run away from it and hide where you haven't applied Neem oil (the buds), so it is better you don’t use it.

Also, plants absorb neem oil and it stays in their vascular system and can alter the taste and flavor of your buds, so it’s better to use the alternatives given in the table above before applying Neem oil.

3. How and when to apply Neem oil

Neem oil can be used as a foliar spray and used as a drench to water the soil in any stage of cannabis’ plant growth (although it is not recommended on the flowering stage), it has shown to be more effective as a foliar spray but will depend on what you’re using it for.

 

 Organic pesticides for cannabis: Plant covered in Neem oil

Neem oil can be used as a foliar spray or a drench, the best way will depend on what you're dealing with.
 

If your plants are suffering from fungus gnats larvae or other bugs that live in the soil, you can use it as a drench, Neem oil will last up to 22 days in the soil but only 45 minutes when mixed with water to be used as a foliar spray.

So depending on what you’re using it for, you will have to repeat the process a couple of times.

Neem oil against bugs

A Neem oil insecticide is super effective against more than 200 kinds of bugs including Aphids, Mealybugs, and Whiteflies.

So, how does Neem oil work?

Despite not killing bugs automatically, this organic pesticide can prevent insects from feeding, larvae from maturing, reduces mating, and can also coat the bugs, preventing them from breathing.

 

Organic pesticides for cannabis: Neem oil can be used as a pesticide

Neem oil can be used both as a pesticide and a fungicide.
 

Depending on your case (if you’re preventing or controlling a pest) and the percentage of Neem oil present in the product you’re using you should dilute it in water, for example, a product that contains 70% Neem oil should be mixed at a ratio of 7ml per liter of water and used as a drench or sprayed throughout all the plant, including the underside of the leaves.

If you’re using it as prevention, you should use it once a week or even once every two weeks but if you’re trying to control and eliminate bugs already present it should be used once every 5-7 days.

Neem oil as a fungicide

There are several ways of dealing with fungi, and Neem oil is one of them. 

A Neem oil fungicide can be used to treat Root rot and Powdery mildew but will depend on the stage your plant is in, if your plant is in the vegetative stage you’ll be fine but if it’s in the flowering stage you should avoid using it.

Is neem oil safe for flowering plants?

Even though Neem oil is safe for flowering plants, it will alter the taste and aroma of the flowers.

 

Plants can absorb Neem oil so you shouldn't spray flowering plants because it will alter taste and smell.
 

Neem oil has a really strong and unpleasant smell and taste, it is not recommended to use it either as a foliar spray or in the soil in the flowering stage because neem oil is absorbed by your plant and it will stay in the vascular system for a while.

If you need to treat fungus or bugs in the flowering stage you’ll be better off using alternatives such as mixing alcohol or baking soda with water.

Is neem oil safe for humans?

Since Neem oil is very potent, it is not 100% safe for humans and animals. Ingesting as little as 20ml can cause vomiting and convulsions. Even though it may seem a bit crazy to drink Neem oil, there have been lots of cases of Neem oil toxicity and it can also affect liver and fertility.

It is advised children and pregnant women stay away not only from Neem oil but from all Neem products in general.

In some parts of Europe (like the UK) the sale of Neem oil is controlled and regulated, so even though it’s organic and considered safe, you should always avoid touching your face when dealing with Neem products.

4. When not to use Neem oil

You should not use Neem oil on plants that have suffered from overwatering, overfeeding, or nutrient deficiency stress recently, even though you can if you need to control a pest fast, it’s better to wait until your plant completely recovers before applying it.

 

Organic pesticides for cannabis: Neem oil used as a foliar spray

Preferably, you should use Neem oil with the lights off and with a temperature of around 20oC.
 

Also, you should not spray neem oil with the lights on (if you’re growing indoors), plants in direct sunlight outdoors or in extreme cold or hot should not be sprayed with neem oil because it can burn the leaves, branches, and stem, you should apply it at night or when the sun sets, and when the temperature is around 20oC to avoid having problems.

5. In Conclusion

Neem oil is a great way to get rid of pests organically, but make sure you don’t use it in the flowering stage because it will affect the smell and flavor of the buds and leave them with an unpleasant harsh smell.

There are alternatives to Neem oil use in the flowering stage if you want to keep your harvest safe. If you've had a good (or bad) experience with Neem oil or have other homemade recipes please leave us a comment below!

External References

1. US National Library Of Medicine National Institutes Of health

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3841499/

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