Neem Oil For Plants: Usage Guide (Including Neem Oil Spray For Plants)

By Jessica Nolan, Gardening Expert Gardening And Landscaping

Neem oil is a natural plant insecticide and fungicide. A neem oil spray can help control and eradicate common houseplant pests. Also, spraying neem oil on leaves can reduce foliar fungal infections to keep your plants looking healthy and thriving. The beauty of neem oil for plants is that it’s easy to use, not toxic, and highly effective.

Why should you use neem oil on plants? Spraying plants with neem oil is a better alternative to using synthetic pesticides. Many manufactured pesticides contain potentially dangerous chemicals that can affect your health. Apart from the dangers of synthetic insecticides, many plant bugs develop resistance to these chemicals. And toxins in many pesticides kill beneficial insects as well as pests.

This article is a complete guide to using neem oil on houseplants, garden plants, and greenhouse plants. You will also find helpful recipes to make your own neem oil sprays at home. Read on to learn how to use neem oil for bug control and improving plant health.

What is Neem Oil?

Neem oil is a natural pesticide extracted from seeds that grow on the neem tree Azadirachta indica. Azadirachtin is the active neem oil component that contains insecticidal properties. This natural plant chemical acts as a useful plant insect repellent. Neem oil also reduces insect feeding and interferes with their hormones and reproductive cycle.

Neem trees are native to India. The neem oil is pressed from seeds contained in the neem fruit. These small drupes look like olives and grow up to 1.1” (3 cm) long. As well as being effective for keeping bugs off plants, neem oil is used in traditional medicine.

Neem Oil for Plants

Neem oil works as a pesticide and fungicide on houseplants and garden plants. Neem oil spray solutions are effective against aphids, various types of mites, fungus gnats, mealybugs, tomato hornworms, and Japanese beetles. Neem oil’s fungicidal properties help destroy fungal diseases such as powdery mildew, leaf spot, tip blight, and scab.

What plants should you not use neem oil on?

Despite being a natural solution, neem oil isn’t suitable for some types of plants. For example, neem oil foliar sprays can burn leaves on some plant species. Also, after repotting, some plants can get stressed, and you should avoid treating those plants with neem oil.

However, neem oil is suitable for treating most species of plants. You can spray neem oil on plants such as fruit trees, ornamental houseplants, vegetables, herbs, and nuts.

How to Apply Neem Oil as a Soil Drench

Neem oil is also useful as a soil drench. Soaking the soil with a neem oil solution helps eradicate fungus gnats, treat soil fungus, and kill bug eggs and larvae in the soil. All you need to do is replace your regular watering with a neem oil mixture. Apply the soil drench every seven days to rid your plants of pest infestations.

To use neem oil as a houseplant bug prevention, you should drench the soil every three weeks.

Neem oil is so versatile that it works as a houseplant soil drench and a foliar spray for plants.

How Neem Oil Works as a Pesticide

Neem oil contains a natural contact insecticide and repellent called azadirachtin. This natural compound works by interfering with the lifecycle of many pests, bugs, mites, and insects. Neem oil disrupts insect feeding and reproduction, which reduces and eventually gets rid of pesky houseplant bugs.

A 2016 study reported that neem oil has over 100 active compounds, many of which have an insecticidal effect. Researchers found that azadirachtin inhibits feeding that eventually leads to weakness and death. Neem oil also stops pests from reproducing and weakens winged insects, so they have difficulty flying.

Another study in the journal Scientific Reports found that neem oil has lethal effects on many types of insects. Neem oil applications on insects inhibit growth and result in pest mortality.

Neem oil controls pests and insects in the following ways:

Neem oil disrupts the laying of eggs
Neem oil prevents larvae development
Neem oil deters feeding on plant foliage
Neem oil repels insects and larvae
Neem oil is poisonous to insects in all stages of growth
Neem oil inhibits the ability to swallow

The benefits of using neem oil as a natural insecticide are that it doesn’t kill beneficial insects or pollinators. So, you can safely use neem oil in your garden or house without worrying about killing bees, butterflies, and ladybugs.

What Bugs Does Neem Oil Kill?

Neem oil kills insects that feed on plant leaves, and spraying whiteflies, aphids and mealybugs helps destroy them on contact. The natural insecticide azadirachtin in neem oil also kills bugs that have developed resistance to synthetic chemical pesticides. There are very few types of plant pests that neem oil isn’t effective on.

Scientific research has found that neem oil is suitable for natural pest control on many levels. The most important way that neem oil kills bugs is by preventing larvae from developing. On some pests, neem oil has a repelling effect and prevents insects from feeding.

Here are some of the 200 pest species that neem oil kills effectively:

Aphids
Whiteflies
Scale insects
Thrips
Fruit flies
Colorado potato beetles
Fleas
Mosquitos
Japanese beetles
Various types of caterpillars
Fire ants
Weevils
Squash bugs

Is Neem Oil Safe?

Neem oil is a non-toxic, natural pesticide that you can use safely in the home and garden. There is no evidence that neem oil is harmful to humans. Also, the active pesticide compounds in neem oil won’t harm birds, bees, fish, or other wildlife. So, when used properly, neem oil is safe to use in organic and traditional gardening.

According to the National Pesticide Information Center (NPIC), neem oil can cause some skin irritation. However, there is no evidence that coming into contact with neem oil or azadirachtin causes cancer or results in other serious health issues.

Neem Oil Spray

Spraying diluted neem oil is the most common way to treat pests, mites, and flies on plants. It is easy to make a neem oil spray with some warm water and liquid Castile soap. Or you can buy commercial neem oil spray. However, making your own spray is usually better.

Here are several reasons why making a DIY neem spray is more advantageous than buying a commercial neem oil spray:

You can adjust the levels of azadirachtin to boost the potency of neem oil sprays.
Neem oil commercial sprays are not always available.
Homemade neem oil sprays are more cost-effective than ready-made ones.

How to Make Neem Oil Spray

Make a neem oil spray with three ingredients—neem oil, liquid Castile soap, and warm water. Mix 2 tsp. neem oil and 1 tsp. liquid soap with 1 quart (1 l) of lukewarm water. Put the ingredients in a spray bottle and shake vigorously to combine them.

With the neem oil spray recipe, the addition of liquid Castile soap helps bind or emulsify water and neem oil together. Always shake the spray bottle before using it to mix the ingredients.

How to Use a Neem Oil Spray on Plants

Spray plants with neem oil weekly to deal with pest infestations. For preventative pest control measures, spray plant foliage—including the leaf undersides—every three to four weeks. Because neem oil disrupts the pests’ lifecycles, you must spray plants regularly to get rid of the bugs.

Here are some handy tips when spraying plants with neem oil:

Always test a small area of the plant’s foliage before treating the whole plant. Neem oil can burn some plant’s leaves.
Thoroughly coat foliage to target all insects and fungal diseases.
Avoid spraying neem oil on plants in direct sunlight.
Spray garden plants in the evening or early morning when the sun isn’t so intense.
Don’t use neem oil to treat plants suffering from overwatering or underwatering.

Using Neem Oil on Houseplants

Homemade neem oil sprays are an excellent non-toxic solution to get rid of houseplant pests. The easiest way to use neem oil on indoor plants is to spray both sides of the leaves liberally. Use regularly to get rid of scale bugs, mealybugs, thrips, or aphids.

If you suspect mold in soil or fungus gnats, use the neem oil solution to drench the potting mix.

Using Neem Oil on Garden Plants

Treat vegetables, fruit trees, and ornamental garden plants with neem oil. You will have to make a larger neem oil solution to use as a foliar spray. Use the ratio of 2 teaspoons neem oil for every quart (liter) of water. Add some liquid soap to help the oil and water emulsify.

Fill a large pump spray bottle with the neem oil liquid. Liberally spray plant foliage weekly to get rid of whitefly, caterpillars, aphids, or other garden pests.

How Often to Use Neem Oil on Flowers and Plants?

Use neem oil insecticides as often as once a week to kill plant pests. It’s good to remember that azadirachtin works gradually. So, you will have to use the solution regularly for at least a few weeks to kill insects, their larvae, and eggs.

Apply neem oil less often—usually every three weeks—to prevent insect infestations. Generally, neem oil is good to use as often as every month at the end of summer and early fall. This is the time when houseplant pests proliferate indoors. With some neem oil prevention, you can avoid dealing with the consequences of thrips, aphids, or whitefly.

Neem Oil Spray – Precautions

Natural neem oil biopesticide is generally safe pest control for houseplant and garden flowers. When appropriately used, neem oil is safe in the home and garden. Of course, you should never ingest neem oil or inhale it. And it’s a good idea to use reasonable precautions to protect your skin and eyes.

You can use neem only on almost all houseplants and landscaping plants. It’s advisable to test a small area of plant foliage first. Neem oil sprays can damage some plant leaves. So, after testing a few leaves, leave the neem oil for 24 hours, and check for leaf burn.

Neem Oil as a Natural Fungicide

The fungicidal properties of neem oil spray mean you can use it to treat powdery mildew and other fungal plant diseases. Other fungal issues that neem oil resolves naturally include leaf spot, tip blight, black spot, and scab. To remove fungal infections from foliage, spray the leaves weekly until fungus signs have gone for good.

The benefit of using neem oil as a fungicide is that it’s safe for vegetables and fruits. The residue on plants doesn’t cause any harmful effects. However, as with all fruit and vegetables, you should wash them before eating them.

Use Neem Oil to Fight Bacterial Disease on Plants

Another way of using neem oil sprays on garden plants is to eradicate bacterial diseases. For example, fire blight destroys plant foliage, causing it to wilt and decay. You can use neem oil as a dormant spray to help prevent fire blight.

Researchers from Utah State University say that neem oil or insecticidal soap can help prevent fire blight. Backyard growers should spray trees with a neem oil solution when fruit trees bloom.

Neem Oil as a Dormant Spray

Spray garden plants with neem oil during the dormant season to kill pest eggs that are overwintering. Mixing two teaspoons of neem oil with a quart of water and some liquid soap can create a foliar spray. Liberally spray leaves that are prone to aphids, caterpillars, mites, or scale insects.

Use the neem oil solution to spray the tree or plant buds about three of four weeks before they begin to swell. For some fruit trees, you should wait until the bud starts swelling. Spray enough of the neem oil solution to coat the upper limbs thoroughly.

Neem Oil for Lawn Grub Control

Neem oil is an excellent natural solution for organic lawn care. Neem oil has pesticidal properties against common bugs that destroy lawns. For example, azadirachtin kills Japanese beetles—pests that feed on grass roots and destroy lawns.

Apply neem oil solutions to lawns every two weeks and after each rainfall to prevent Japanese beetles. If you notice bare patches of grass, you can also use neem oil soil drenches to help kill off Japanese beetles.

One study found that azadirachtin in neem oil is a viable control option for Japanese beetles and other root-feeding pests.

Use Neem Oil to Eradicate Pests on Vegetables and Fruit Plants

The fungicidal and pesticidal activity of neem oil makes it the best natural treatment for vegetables and fruit plants. Spraying greenhouse plants or vegetables in your garden can help control pest infestations. Regularly spraying neem oil on vegetables can kill hornworms, aphids, and whiteflies.

Neem Oil Solutions Protect Fruit Trees from Pests

Use neem oil to stop pests from affecting fruit trees growing in your backyard. Fill a large spray pump bottle with a neem oil solution. Liberally spray the apple, pear, plum, or other fruit trees before they blossom. Repeat the application after the petals drop. Then spray the growth or fruit buds as often as every two weeks to keep fruit trees pest-free.

Neem Cakes are Excellent Garden Fertilizers

Organic neem cakes are some of the best natural fertilizers for your garden. Neem cakes are high nitrogen bio-fertilizers with traces of potassium and phosphorus. Fertilizing soil and lawns with neem cakes helps improve soil texture, provide plenty of nutrients, and aerate the soil.

You can use neem cakes in organic gardening by amending the soil in vegetable patches. Work in neem cakes to the recommended concentration to improve the ground and eliminate harmful nematodes.

To improve the appearance of turfgrass, mix one tablespoon neem oil with a gallon of water. Fill a spray pump bottle with the neem soil solution. Apply the solution to your lawn to fertilize it.

Neem oil vs. Insecticidal Soap

Neem oil and insecticidal soap work in similar ways to kill houseplant and garden plant pests. Insecticidal soap and neem oils suffocate insects to kill them. In one experiment, neem oil solutions were more effective than insecticidal soaps at eliminating fire ants.

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