How to Use Neem Oil on Plants as Organic Insecticide + DIY Recipe

Last Updated on November 3, 2021 by Admin

If you’re looking for non-toxic pesticides that you can use indoors for your houseplants during the winter or in your garden, consider neem oil. It is simple to use without the harsh and dangerous chemicals many commercial pesticides contain. In this article I will show you how to use neem oil on plants as an organic pesticide including DIY recipes you can make at home.

But in order to understand how to properly use neem oil, it is important to learn what makes it effective against pests and fungal problems in plants. This way, you know how to use it, when to use it as well as how not to use it.

Table of Contents

What is Neem Oil?

Neem oil comes form the Neem Tree (Azadirachta indica), which is a member of the mahogany family. The tree is a native to India and countries in Africa.

It is extracted from different parts of the tree which is also used to create was, soaps and for cosmetic products. The seeds contain the highest concentration of insecticidal properties, which is why they are pressed to create the oil.

For this reason, gardeners like to use neem oil to eliminate pests and fungi from plants. Its insecticidal properties not only allow it to get rid of pests but also keep them away. Additionally, it makes it harder for these critters to lay eggs.

Neem oil is often sold in concentrated form. You’ll find it in different stores packaged in bottles.

But, to use it as an organic pesticide it needs to be diluted with water since the original concentration is too potent for the plants. On its own, it can damage the plant by causing leaf burns.

There are also ready to use sprays as well which are already pre-mixed. These are more convenient. But, they come out to be more expensive because in part you’re paying for the water that’s mixed in.

So, many gardeners prefer to buy 100% pure neem oil and mix it themselves.

Finally, it is worth noting that as useful as neem oil is as an organic pesticide, it can cause acute harm to people and other mammals. This is especially true if the oil is used in its concentrated for. Although the effects only last as long as neem oil is continuously ingested in high doses.

Once exposure stops, recovery starts to happen with no long term consequences.

I’ll discuss more about neem oil safety below.

How to Use Neem Oil in the Garden

Neem oil is most effective when used as a spray on leaves. It can last up to 22 days when sprayed on soil but much shorter in water.

It is almost non-toxic to garden wildlife which makes it relatively safe even if you have birds, bees or even fish around your garden.

Neem oil is very effective as an organic pesticide. As mentioned, it not only gets rid of pests but also prevents and keeps them away.

Unfortunately, neem oil is not as effective in being able to help plants recover from severe infestations. Thus, it is best used to prevent pests from coming around. Or, it is to be used as soon as possible when you spot any signs of the pests or the damage they inflict.

In short, the earlier you catch the pests the more effective neem oil will be. Its effectivity decreases as the size of the infestation grows.

So, for larger infestations, you’ll want to use neem oil in conjunction with other pest treatment methods for best results.

What Types of Pests and Diseases is Neem Oil Effective Against?

Neem oil is effective against the most common garden pests including mealybugs, aphids, thrips, whiteflies and scale. Additionally, it works very well against 200 other pest species, insects and bugs that are known to chew or suck on plants.

It works best against soft-bodies pests as the neem oil and water mixture will coat their bodies and eventually kill them. It also prevents them from feeding and reproducing.

But, the key to its effectively is direct contact. This is when it is most potent against these insects.

The best part about neem oil is it does not harm beneficial insects including butterflies, earthworms, bees and ladybugs. Again, the key is not directly spraying them with it.

This is why most gardeners use neem oil later in the day often in the evenings when the beneficial insects are not active. This prevents them from being victims of “friendly fire”.

Additionally, neem oil is also a potent fungicide which is why many growers use it to get rid of and prevent different types of mildew, fungus, black spot, blight, leaf spot, botrytis, rusts and a few others.

It makes plants less prone to these fungal diseases and keeps them from spreading.

That said, its effectivity as a fungicide is very similar to its ability as a pesticide. That is, it is most effective in prevention and for use in the early stages. It becomes less effective once a disease outbreak is in full swing.

How Does Neem Oil Work and When to Apply It?

When it comes to neem oil’s pesticidal properties, the most active ingredient is Azadirachtin.

According to research, Azadirachtin has the following benefits making it effective as a pesticide.

It interferes with their hormone systems preventing hem from laying eggs
Deters their feeding ability
They’re less able to mate
Repels insects

Unfortunately, with neem oil, most products will not tell you how much Azadirachtin is contained in their products. Because store bought products always contain other ingredients, the concentration often varies per brand.

Neem oil kills some pests when they eat leaves that have been sprayed with it. It also has a strong scent which repels other insects.

When to Apply Neem Oil

Neem oil is best used as a preventive measure. So, it works very well to repel and keep pests from plants that are more susceptible.

Also, it is most effective in the early stages when you see problems happening, especially before they turn into full-blown infestations.

But, be careful when you apply. Always test before you apply it to an entire plant.

Depending what kind of neem oil you buy, the concentration will be different.

Ready to Use Neem Oil – If you get the ready-to-use sprays, they’ll be pre-mixed. These are more expensive because water and other ingredients have been added to dilute the neem oil. This makes it viable for plants in that the neem oil is not overly potent that it will damage the plant. This is the most convenient to use.
100% Neem Oil – to save money, many gardeners will buy the 100% concentration of neem oil. This is “pure” neem oil and it is too strong to be directly used on plants. So, you need to dilute with water which I’ll show you how to do below. You want to avoid using too much neem oil because it will burn the leaves of the plant.

Whichever kind you decide to use, always test a small section first. You can spray a small portion of the plant and wait 24 hours. If there is no damage to that area, then the concentration will be safe enough to use without damaging the plant.

Note that plants, like people, have different sensitivities. Some are more hardy and can take more concentrated doses while others are more delicate. So, always test each individual plant and don’t assume that one safe test result means it will not be harmful to all your plants.

Another thing to consider is neem oil’s effect in related to the environment.

It is best applied in the morning or evening under indirect light to avoid burning the leaves. Doing so also prevents too much of the neem oil from evaporating too quickly.

You want to avoid applying neem oil when:

The weather is very hot or very cold
The plant is stressed
Plants are overwatered or underwatered/experiencing drought

When there are pests or fungal problems, apply the neem oil spray (recipe below) once a week.

For prevention, apply once every 7 to 30 days depending on the type of plant. In most cases, once every 1 to 2 weeks works to repel the pests.

How to Make Neem Oil Spray – DIY Neem Oil Recipe

When it comes to neem oil for plants, you can buy the ready-to-use commercial sprays that are available in stores. These are the easiest to use since everything is pre-mixed.

However, if you’re going to use neem oil on many plants or on a regular basis to keep pests away, a more cost effective way is to get a container of pure neem oil. This is 100% neem oil concentration.

Then you mix in batches into spray bottles whenever you need it.

This is cheaper in the long run since you don’t “buy” the water that’s diluted into the ready-to-use spray products.

Ingredients and Equipment Needed to Make Neem Oil Spray

Here’s what you’ll need to make your own Neem Oil Spray for houseplants and garden plants.

5 teaspoons of concentrated neem oil
1 teaspoon of mild liquid soap (I like to use pure castile soap in liquid form, look for Bronner pure castile soap).
1 liter of water
Spray bottle

A few notes on the ingredients.

There are a few brands of castile soap that work really well so you can choose which one works for you. Quinn’s and Cove are two other products I’ve had good success with besides Dr. Bronner’s.
I used smaller units for the formulation so you can use them for houseplants. If you need to make bigger batches for your garden, go with a garden sprayer or handheld sprayer. Then, just scale up the amounts while keeping the proportions.
Some people use the neem oil without the liquid soap which also works although I’ve found that the soap enhances its pest killing properties especially if you already have pests attaching the plant.
The soap also helps emulsify the oil with water. If you cook or wash the dishes by hand, you know oil and water don’t mix. So, the soap helps them to mix thoroughly. Some people use silica or potassium silicate.
Some people like to use dish soap like Dawn. If you do, try to start with lower concentrations because these tend to contain additives, fragrances and other ingredients that can harm plants.

Mixing Instructions

Mix all the ingredients into the spray bottle and shake thoroughly.

Test the Mixture

Once you’re done always test the mixture.

You can do this by spraying 1 to 2 leaves preferably not beside each other so you can be sure that there’s less of a connection between the two.

Wait 24 hours, then check the leaves.

If you see any damage including yellow or brown spots where you sprayed, it means the mixture is too strong for that particular plant.

An easy fix is to dilute the mixture with a bit of water then test again. Adjust the solution proportions as needed.

Since different plants have different sensitivity levels (just like some people have sensitive skin), I like to test each plant fore spraying them with the mixture.

After you’ve done it once, you’ll know which plants are okay or not.

How to Apply Neem Oil Spray to Plants

When the tests show on damage to the plant, it is time to spray the plant with the neem oil solution.

You want to be through, spraying the leaves including the bottom sides which is where many of the pests lay their eggs and also hide because it’s harder to spot them there.

When applying drench the plant and leaves. Also, keep shaking the bottle to keep the solution well mixed.

Keep the plant away from sunlight. Also, avoid doing so when the weather is very hot. I like to apply it early in the morning or later in the afternoon and night. Both times are cooler than the middle part of the day where the oil can increase the risk of burning the plant’s leaves.

Apply every 7 to 14 days depending on the pest status of the plant.

If there are pests, apply once a week. Avoid overdoing it since too much of the neem oil and castile soap will eventually harm the plant. So, try not to spray too frequently.

Keep applying once every week until the pests are completely eradicated.

If you’re preventing pests, once every 1 to 4 weeks works.

Safety Gear

If you have sensitive skin, it is a good idea to wear gloves and long sleeves while spraying. You can also go with long gloves instead to keep your skin from getting in contact with the neem oil.

It can cause skin irritation to some people or allergies.

I don’t wear any gloves when I apply since I don’t have any problems. So, this one is up to you depending on how you feel.

If you’re not sure, I suggest playing it safe.

Is Neem Oil Safe?

The last part of this article will focus on safety of neem oil.

Like all things, when neem oil is used properly, it is safe. The oil itself is non-toxic. But, it is not to be ingested for any reason at all.

Studies has shown that it poses no risk of cancer or other diseases. This makes it much safer than pesticides with chemicals in them.

That said, always be aware if you use it. I like to make sure to thoroughly wash any vegetables I’ve grown in the backyard that have come into contact with neem oil before cooking or using them for salads.

You want to keep it away from your eyes as well since it can cause irritation. Since spraying outdoors puts you in the mercy of the wind, using safety glasses is a good way to keep the oil away from your eyes even if a sudden gust of wind blows when you’re spraying.