Using neem oil as a pest control option for plants has become increasingly controversial.
Some people fully believe that neem is an effective part of pest control and others believe that it is a hoax and should only be used for leaf shine, if at all.
There are, of course, lots of people in between these polarized perspectives.
But what is the truth of the situation? What do studies conclude with regards to neem oil and pest control?
That’s what this post aims to dig into and discuss, using research to answer the question rather than opinion.
Table of Contents
- What is neem oil?
- How does neem oil impact houseplant pests?
- Is neem oil actually proven to be effective at pest control?
- How do you use neem oil effectively?
- What houseplant pests can neem oil help to control?
- What is my personal opinion on using neem oil as a pest control option?
- Related Posts
What is neem oil?
Neem oil comes from the neem tree, Azadirachta indica, which is native to the Indian subcontinent.
Neem tree products are used in lots of ways beyond leaf shine and pest control. Neem is in some shampoos, make up products, toothpastes, and has been used medically for patients with diabetes, acne, and other dermatological issues.
The oil from neem trees has been used to control plant pests for hundreds of years (Source: University of New Hampshire, 2020)
It is important to note that neem oil can interfere with a person’s hormones (just as it can interfere with a bug’s hormones). (Source: National Library of Medicine, 1997)
How does neem oil impact houseplant pests?
Neem negatively impacts pests in several ways:
- Neem oil disrupts a pest’s drive to feed
- Neem affects the pest’s hormone regulation, which impedes growth and slows the drive to procreate
- The oil can also coat the pest and suffocate it, but the bug really does need to be fully coated for it to be effective
- Lastly, neem also repels pests
Source: National Research Council (US) Panel on Neem, 1992
Is neem oil actually proven to be effective at pest control?
Yes, researchers have found that neem oil is effective at pest control when used and applied properly. (Insecticidal Effects of Neem Oils Obtained from Neem Berries Stored at Different Periods, 2013)
In fact, it has been found to be effective even on bugs that have developed resistance to other control products. (Source: National Research Council US Panel on Neem, 1992)
[Neem seed oil] reduces insect feeding, growth and egg laying. It also acts as a repellant. […]
[Need seed oil also] reduces fungal infection by preventing spore germination and penetration.Skelly, J. 2013, Horticultural Oils – What a Gardener Needs to Know, Extension | University of Nevada, Reno, FS-13-20
Neem oil is most effective at controlling young and immature bugs, preventing them from developing properly. Through repeated applications, neem oil can prevent young generations from reaching adulthood and successfully procreating.
One study also looked at how the effectiveness of neem oil changes over time because neem is known to degrade rather quickly.
The research concluded that neem oil only changes slightly in effectiveness when used within 7 years and stored at room temperature. (Source: Insecticidal Effects of Neem (Azadirachta indica A. Juss) Oils Obtained from Neem Berries Stored at Different Periods, 2013)
Please note: Neem oil is a slow-acting pest control option that requires repeated applications to be effective. Because of this, neem oil may not be a great treatment option for heavily infested plants as it may not work fast enough to control the problem.
How do you use neem oil effectively?
Neem oil is effective when strategically applied multiple times AND when emulsified in water with an oily soap.
Why do you need to apply neem oil multiple times?
Because neem oil is most effective against young and immature bugs, the adults could continue to live and produce more offspring. To ensure that neem oil has the upper hand, it should be reapplied to control future generations and bugs who snuck by the last application.
Source: Efficacy of Neem Oil on Cardamom Thrips, Sciothrips cardamomi Ramk., and Organoleptic Studies, Psyche: A Journal of Entomology, 2014
How often to apply neem oil?
Depending on the pest, eggs can hatch anywhere from 2 to 14 days. Apply neem once or twice a week for 4 to 8 weeks to eliminate new generations and any newly hatched eggs.
4 weeks will do the trick in most cases, but there are some pests that can live up to 6 to 8 weeks (like thrips and whiteflies) so neem could be applied through the 8 week mark to ensure success.
How do you make a homemade neem oil spray?
The homemade spray combines only three ingredients:
- 16 ounces of warm water
- .5 teaspoon of a mild dish soap
- .75 teaspoon of 100% neem oil
To ensure the spray is effective, emulsify neem oil in water using a mild dish soap.
Here are Amazon affiliate links to the products I use for my homemade spray:
Dr. Bronner’s Peppermint Castile Soap
I use peppermint-scented soap because peppermint is a pest deterrent. The unscented soap can be used.
Sally’s Organics Glass Spray Bottles
Why does neem oil need to be emulsified in water with an oily soap?
Because oil (neem) and water do not mix well, an ingredient is added to help. In this case, adding an oily soap provides a way for the neem oil to disperse more evenly throughout the water.
The more evenly neem oil is dispersed in the water, the better it will be able to coat the plant.
How do you properly emulsify neem oil?
To emulsify neem oil, first mix the mild dish soap and the neem oil together thoroughly by stirring.
Then add this mixture to the warm water in a spray bottle and shake vigorously.
You will know the spray is fully mixed when there are little to no oil droplets on the surface of the water.
How do you properly apply the neem oil spray?
#1 Apply a neem oil spray to plants when they aren’t currently in direct sun, as the plant becomes more prone to burn when coated in oil.
#2 To ensure the utmost safety for the plant, spray a small portion of the foliage to see if it can tolerate neem oil.
Some plants are sensitive to this treatment and do not fair as well (for example, ferns have not tolerated neem well for me).
#3 When you are ready to spray a plant, try to cover all surfaces of the plant, especially the places where pests can hide (nooks, crannies, leaf undersides)
#4 Plan to reapply once or twice per week for several weeks or until you no longer see any pests
Source: Texas A&M Agrilife Extension, Using Oils As Pesticides
What houseplant pests can neem oil help to control?
Neem oil can be used to control thrips, spider mites, aphids, whiteflies, mealybugs, the immature stages of scale, and more.
Neem oil can also be used to treat powdery mildew and may help to reduce other fungal and bacterial issues.
Source: Clemson University, HGIC Horticulturalists, Karen Russ and Joey Williamson, Less Toxic Insecticides, 2019
What is my personal opinion on using neem oil as a pest control option?
I have been using neem oil as a pest preventative and as a way to treat small pest infestations for years with lots of success.
I’ve also used neem to help treat large infestations on small plants by coating the plant and the placing it in a closed zip lock bag with air blown into it, suffocating the pests. I have never seen any other plant person talk about this method, so this is just anecdotal.
Do you use neem oil for pest control? What has your experience been? Tell us in the comments!