What is Neem Oil: How to Use Neem To Protect Plants

Neem oil and neem berries in a mortar and pestle
Photo Credit
M. Kumar/Shutterstock

Using Neem Oil as an organic pesticide

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Neem oil is a nontoxic pesticide that many gardeners say is their magic bullet to getting rid of bad bugs on plants (without harming anything else). Learn how to use Neem oil in the garden as well as some cautions with Neem oil. 

What is Neem?

Neem oil is extracted from the seeds of the neem tree (Azadirachta indica). An evergreen forest tree native to the tropical lowlands of Myamar, Sri Lanka, and India, neem has been used as a pesticide for hundreds of years. It also has been a part of traditional medicine in those countries where it is considered a cure-all for most diseases and ailments. In Indian mythology, it is said to be of divine origin and its Sanskrit name means “reliever of sickness.” It has been shown to have antibacterial and antiseptic qualities and is an ingredient in soaps, cosmetics, toothpaste, and pet shampoo.

branches from a neem tree
Related to mahogany, neem has been referred to as “Nature’s pharmacy.”

The major active ingredient in neem is the chemical azadirachtin which is present in almost all parts of the tree but is most concentrated in the seeds. Once the seeds have been processed and it has been extracted, the remaining oil is marketed as clarified hydrophobic neem oil—often shortened to just neem oil on product containers. There is still a bit of azadirachtin present but not as much as in a product that is sold as having azadirachtin as the major ingredient. Products containing high amounts of azadirachtin are used primarily by commercial growers while home gardeners usually have access to neem oil sold at garden centers. It is less toxic and generally regarded as safe (GRAS) by the FDA.

neem tree and white neem flowers
The neem tree has fragrant white flowers and fruits that look like small olives.

How Does Neem Oil Work?

Neem oil works in different ways.

  • Like any oil, it suffocates bugs that get covered in it. It is most effective on immature insects and larvae. Adults may survive so you need to time your application right. It also works well on caterpillars, leafhoppers, whiteflies, mites, aphids, mealy bugs, thrips, leaf miners, and scale, and can kill eggs. It takes time to work; the effects are not immediate.
  • When the plant has been thoroughly sprayed, some of the oil will be absorbed and it will act as a repellent to disrupt feeding by chewing and sucking insects.
  • It also is a growth regulator, can inhibit mating, and impair the ability to reproduce which will slow an infestation down.
  • As a fungicide, neem can be used to prevent or stop fungal diseases including rust, black spot, sooty mold, and powdery mildew. If the plant is already infected it won’t cure what is there but will keep spores from spreading further.
neem oil spray in a white bottle with purple pansies and gold marigolds
Neem Oil spray can be found in almost all garden nurseries. 
Credit: Shutterstock

How Do I Use Neem Oil on Plants

Neem can be purchased as a ready-to-use spray or a concentrate that needs to be diluted first. Prepare it as directed.

Neem oil is a botanical insecticide made of natural tree oil, harvested from its seeds, and has a low toxicity rating. It’s safer to use than a synthetic pesticide but it is still not totally safe. Follow the cautions on the label. Limit your exposure to the spray by wearing gloves, a mask, and eye protection. Don’t inhale the mist.

Make sure it is labeled for the insects you want to use it on and for the location you want to use it in. Are you using it inside your home, outside in the garden, or in a greenhouse?

 To be effective, the plant needs to be totally covered. The best time to spray is in the early evening when the sun is low and the bees are less active.

Cautions With Neem Oil

Neem oil is still toxic to bees that are exposed to direct treatment, so please don’t apply it if they are present. Test a leaf and wait a day to see if it is damaged by the spray. If it is fine then spray carefully.

Also, don’t use neem oil on plants that are already stressed. The oil degrades quickly so you will have to reapply it as often as every 7 to 14 days or as directed.

It is harmful to fish and aquatic mammals so do not use it near water.

Do you use Neem oil? Please share your experiences below! Thank you.

Read more about other natural solutions used in the garden, such as Epsom Salts.


About The Author

Robin Sweetser

Robin has been a contributor to The Old Farmer’s Almanac and the All-Seasons Garden Guide for many years. Read More from Robin Sweetser

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