Chemical insecticides are harsh products that some people prefer not to use on their cannabis. Fortunately, neem oil has come to the rescue. This versatile, organic product is must-have for any grow room and may protect your plants from being invaded by destructive pests. This guide discusses neem oil so you can safely start using it as a preventative measure before any real infestations take over.
What Is Neem?
The neem tree, also known as Indian lilac (Azadirachta indica) is one of two species of tree indigenous to parts of India and Iran, and belongs to the Meliaceae family which includes trees such as mahogany.
The neem grows tall and can reach heights of up to 30-40 meters. It is commonly seen growing in tropical climates where rainfall is It grows flowers and fruits which can be found in some types of Indian cuisine. The leaves are also used in cooking and many believe they are good for the health. The flavour is said to be bitter so neem is typically mixed with other ingredients.
The oil is extracted from the seeds and fruits produced by the neem tree. Neem oil has been used in traditional Indian medicine for many years, however the health benefits are still being researched. It is known to be toxic if consumed over long periods of time.
How Neem Works
Neem oil is predominantly applied as an insecticide. The leaves can even be dried and placed around the home or in food cupboards to ward off pests. Over the years, neem oil has become widely discussed by farmers as an effective antifungal and antibacterial pest control product.
The neem tree has its own defence mechanism which protects it from being attacked by insects. The sap produced by the tree contains azadirachtin, which acts a natural insecticide and has shown to repel hundreds of different types of pests.
Neem oil works by creating an uncomfortable, oily environment for the pests it is being used to control. Unlike most chemical insecticides, neem oil doesn't kill pests straight away. It prevents pests from feeding and affects their ability to grow or lay eggs, which diminishes the population over time. As such, neem oil needs to be applied regularly to keep the pest from multiplying again.
Types of Neem
There are two different types of neem oil commonly seen available for purchase when searching for neem products. Neem oil tends to either be cold-pressed or extracted using alcohol. They are both natural but have different uses.
Cold-pressed neem oil - Typically for making cosmetic products such as soaps due to its antibacterial components. Often in crude form without instruction for use as a pesticide, making it hard to know the concentration or strength.
Neem oil extract - Neem oil for use in agriculture and horticulture is sold specifically as insecticide. The product labels have recommendations for the percentages one needs to use for pest control. Neem oil extracted this way preserves the active compound which interferes with insects, azadirachtin.
Pros and Cons of Neem Oil
Neem oil is very effective when it comes to controlling pests in your cannabis grow space. Outdoors, it can be trickier to manage pests with neem oil. If we are not careful, neem oil can actually be harmful to other beneficial insects that may ingest it, such as ladybugs or bees.
Insects that do not feed on plant material are less affected, but it's important to be aware of how often we apply neem, and when. Indoors it is easier to manage because we have the problem isolated in an environment we have more control over. We also don't risk harming other insects such as bees.
Let's take a quick look at some of the pros and cons of using neem oil:
| Pros |
Cons |
- Can help to improve a plant's natural defence
- Useful for many different kinds of pests
- Keeps pest populations under control
- 100% organic product
- Easy to use
|
- Toxic when used in large quantities
- Not all neem products are safe for plants
- Doesn't always completely eradicate pests
- Can be harmful for beneficial insects
- Requires regular application
|
Treating Cannabis Problems
Neem oil is ideal for organic farmers experiencing pest problems. For cannabis, we need to pay particular attention to our use of neem oil so we control the problem without damaging our final product or other beneficial organisms.
Pests
Neem oil can protect cannabis from the following pests:
- Whiteflies
- Spider mites
- Broad mites
- Thrips
- Aphids
- Fungus Gnats
- Mealy bugs
- Mold
Powdery Mildew
Neem oil has shown to be an effective treatment against powdery mildew. This fungal disease normally appears due to bad air circulation, low light or high humidity, so prevention is best achieved by keeping the correct environment. You can apply neem foliar spray once every 7-10 days during vegetation if you are worried about powdery mildew.
Making Neem Oil Foliar Spray
Neem oil is typically applied as a foliar spray and is usually prepared by combining it with an insecticidal soap and water. The oil does not dissolve easily in the water, so adding an insecticidal soap (specially designed, with no perfume) can aid the process.
A high concentration may be harmful for plants so read the instructions and be careful not to over-do it.
Neem oil products vary in strength, so make sure you check the label before diluting. You only need a very small amount to make the solution.
Steps to making neem foliar spray:
- Fill sprayer with 1l of warm water (room temperature is fine)
- Add 1-2ml of insecticidal soap and gently mix without producing bubbles
- Add neem oil at the recommended strength
- Thoroughly stir the solution
- Use immediately and swish the bottle intermittently to keep the solution well mixed
Neem Oil + Potassium Soap preventative sprays on Girl Scout Cookies (Fast Buds) by Cogollo_eu from GrowDiaries.
Tip: You may need to warm the neem oil up as it can become extremely viscous when temperatures drop below 20°C
How To Use Neem Oil
If you're trying to control a pest problem, neem soil spray can be applied every 3-7 days. Try not to leave it much longer than this otherwise you risk the pests coming back. Unfortunately, most of the time neem oil does not completely rid your plants of pests but it depends on how severe the infestation is and at what stage the pest arrives. The initial goal is to gain control so they do not overpopulate and eventually ruin our crops.
Tips for using neem oil on cannabis plants:
- Use a pressurized sprayer designed for garden use
- Spray the plant from all sides, including the undersides of leaves
- Plants should be wet but not completely drenched
- Make sure you switch off fans when applying foliar sprays
- Allow plants to dry before turning on fans or lights again
- Avoid spraying flowers
It is best not to apply neem oil in the last 3 weeks of flowering. If there is any residue left on the plant during harvest it may affect the quality of the end product. If the infestation you are trying to control is particularly bad in the last weeks of flowering, it might be worth it to consider removing infected parts of the plant or harvest earlier than originally planned.
Tip: To prevent burning your plants with neem oil, avoid using it during the hot, sunny hours of the day. Preferably, apply it as the sun goes down or if you're growing indoors, when your lights are off.
Conclusion
Neem oil is a fantastic product when it is used correctly and we recommend having some available in case you do suddenly come across an infestation. Neem oil might not get rid of the problem, but it will certainly help you take control and hopefully allow you to reach the end of the grow cycle with a harvest.
If you found this article useful, feel free to share your thoughts about neem oil down in the comments section!
External References
A.K. Production of the Biopesticide Azadirachtin by Hair Root Cultivation of Azadirachta Indica In Liquid-Phase Bioreactors. Appl Biochem Biotechnol - Srivastava S., Srivastava (2013)
Variability in Neem (Azadirachta indica) with Respect to Azadirachtin Content, Journal of Agricultural and Food Chemistry - O. P. Sidhu, Vishal Kumar, and Hari M. Behl (2003)
Anti-fungal activity of neem oil. International Journal of Pharmaceutical Sciences Review and Research. - Ahmed, M. & Gayathri, R. & Vishnupriya, V.. (2016).
Neem Oil As Pesticide. Journal of Dispersion Science and Technology.-Waghmare, Jyotsna & Ware, A.. (2007).
Neem oil poisoning. Indian pediatrics. - Dhongade, Ramchandra & Kavade, Sandeep & Damle, Rushikesh. (2008).
This article was updated November 2020.
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