If you’re a gardener looking for organic pest control options, you may have heard about neem oil. There’s a lot of information out there about this natural pesticide, some of which may be confusing.
Let me cover what neem oil is, how to apply it, the risks and benefits associated with neem oil, and which plants should, or should not be treated with neem oil.
What is Neem Oil?
Neem oil is a product obtained by pressing the fruits and seeds of the neem tree, which is indigenous to Southeast Asia. It has a broad history of use in Ayurvedic medicine, and components of neem oil can be found in many household products across the world, such as toothpaste, soaps, shampoo, and cosmetics.
The active component of neem oil is Azadirachtin, which is found in many forms of organic pesticides, including powders, sprays, and pellets. The most common use for application of neem oil by the home gardener is by spraying a diluted mixture on the leaves of plants.
Neem oil works in multiple ways at once:
- By disrupting the feeding insect’s life cycle with regard to reproduction, feeding, and eating.
- As a repellent – Neem oil has a bitter taste and a garlic/sulphur odor.
- By smothering and suffocating the smallest insects, such as mites.
Neem oil works on the full spectrum of insect life stages: adult, larvae, and egg.
It is safe to use around humans and pets in small to moderate amounts, and is considered safe for birds, bees, and ladybugs, if used correctly.
Can Neem Oil Burn or Kill Your Plants?
Novices using neem oil spray often make the mistake of rushing into application without knowing how to prepare a neem oil mixture, applying it at the wrong time of day, and/or applying it too often.
Any of these mistakes can result in your plants being sun damaged, developing “burns”, which appear as white, dry patches on leaves.
Additionally, coating plants too often with neem oil can cause the plant’s leaves to develop a film which can hinder photosynthesis.
In this way, a plant that becomes too damaged could ultimately die, though in most cases, such plants will recover on their own once the gardener corrects their mistake.
There are certain types of plants that are more susceptible to burning or damage from neem oil. It’s best to avoid using neem oil on these plants, or do it sparingly, with a more diluted mixture.
Never apply neem oil when the sun is high in the sky, as direct sunlight on leaves coated with neem oil will result in burning, and always dilute neem oil with water (see preparation of neem oil below).
Plants that Neem Oil Will Burn/Damage:
Plants with delicate or thin foliage should not be treated with neem oil, as they are more likely to burn. Tender seedlings or stressed plants may react badly to neem oil, as well.
Avoid using neem oil on these plants:
Does Neem Oil Always Work to Repel Bugs?
There are some bugs that are less sensitive to neem oil. Leaf-footed bugs, squash bugs, and some caterpillars are very tolerant of neem oil, and you may need to supplement with another organic pesticide, such as BT (Bacillus thuringiensis).
What Insects Does Neem Oil Work Best On?
Neem oil is reported to work on over 170 types of bugs, to varying degrees. It is most effective when treating plants for:
- White flies
- Cabbage loopers
- Fruit flies
- Spider mites
- Colorado potato beetles
- Mexican corn beetles
- Spotted cucumber beetles
- Flea beetles
- Corn earworms
Neem oil is moderately effective against many other insects, as well. You can see a full list of pests it works to control in a PDF by the EPA here.
Plants That Don’t Benefit From Neem Oil:
There are some plants that naturally repel the same insects that neem oil targets. There’s no need to waste your neem oil on the following plants:
Is Neem Oil Generally Safe as an Insecticide?
Neem oil is considered a safe and effective organic pesticide. The EPA has reported that neem oil will not cause adverse effects to humans or other non-targeted organisms when used according to the directions found on the package label.
Neem oil is biodegradable and breaks down very quickly. It will not contaminate ground water or run-off.
That being said, there are certain situations to avoid when using neem oil:
- Avoid coming into contact with neem products if you are pregnant or breastfeeding.
- Neem oil is a mild irritant to skin and eyes. Wear gloves and protective eyewear when spraying.
- Avoid spraying near inhabited bodies of water, as neem oil is considered slightly toxic to fish and aquatic animals.
- Avoid spraying neem oil during full daylight hours when pollinators are at work. Although neem oil is said to be safe for bees, (since they are not eating the active ingredient), the risk is that the bees may come in contact with the solution while it’s still wet, and possibly transport it back to the hive. Only spraying at dusk or dawn is the safest method of application, as the neem oil mixture dries in approximately 45 minutes.
- Avoid spraying or storing neem products around small children or pets, as unsafe quantities could be consumed or inhaled. Children are less at risk for neem product overdose as they grow older.
Plants that are Compatible with Neem Oil:
There are many plants that will benefit from being treated with neem oil, such as:
- Bok choy
- Brussels sprouts
- Collard greens
- Citrus Fruits
- Fruit Trees
- Melons (all types)
- Olive Trees
- Squash (all types)
- Sweet potatoes
- Swiss chard
Neem oil is safe for your fruit trees too, read our related post “Using Neem Oil on Fruit Trees (The Ultimate Guide)” here.
How Do You Safely Prepare Neem Oil for Plants?
Cold-pressed neem oil is the only neem oil that will effectively kill pests, as other methods of extracting the oil will denature the active ingredient (Azadirachtin). Be sure to purchase pure, cold-pressed neem oil, or pre-made sprays that list it as such.
I recommend using Neem Bliss – a Pure Neem oil product available on Amazon.
If using pure neem oil to make your own spray, you’ll need to dilute it. Never use straight neem oil on your plants, as this will damage the leaves.
To one quart of water, add 1 teaspoon of neem oil, and a drop of liquid dish detergent. The soap acts as an emulsifier, separating the oil’s molecules and enabling it to mix more thoroughly with the water.
Shake the mixture up so it’s well incorporated. You can use a plant mister for small applications or mix a larger amount to use in a single or multi-gallon home and garden sprayer.
Don’t mix more than what you’ll be using immediately, as the active properties of neem oil deteriorate quickly.
Spray the foliage and stems thoroughly, avoiding any flowers. The leaves should drip with excess solution. Make sure to spray the undersides of the leaves as well.
Repeat the process once every 7-10 days as a preventative measure. For ongoing infestations, spray your plants every 3-4 days, but keep an eye out for foliage burns. If you start to notice white, dry patches on your plants, increase the time between applications. If it rains, be aware your application has likely washed off.
It may take up to a week to see any results, so be patient. With consistent use, an infestation should diminish drastically within 2-3 weeks.
As noted above, only spray when the sun is low in the sky, at dusk or at dawn. Many people choose dusk as the safest option, as the plants will have plenty of time to dry before pollinators or sunlight returns.
It’s best not to spray neem oil directly before harvesting. Cease neem oil applications at least 48 hours prior to harvesting and wash the produce thoroughly.
Neem oil can be an effective and safe way to rid yourself of many pests in your organic garden. With the right precautions, you can rest easy, knowing you’re not harming the environment or beneficial insects in your endeavors to maintain a healthier, pest-free garden.
Michelle Weaver is a former pastry chef of thirty years who reinvented herself during the pandemic, now happily earning a living through freelance writing and selling her art. She and her significant other live in an 1895 farmhouse in North Carolina, where they have several acres, allowing her to garden to her heart’s content. When she’s not playing in the dirt, she enjoys hiking in the nearby mountains, creating new vegetarian recipes, and photographing the wildlife that comes to visit.