How to Save Your Plants With Neem Oil and Neem Cake
With a Video, "All About Neem Oil"

There are many studies about the dangers and drawbacks of synthetic pesticides.  A quick search online brings a wealth of information about pesticides and their use.  But what do you do if you’re having a problem with garden pests and don’t want to use synthetic pesticides?  Pest control is one of the biggest challenges you can have if you want to maintain a thriving garden.  It isn’t good if you have plenty of healthy plants, but pests are chewing on them.  Using pure neem oil and neem cake can help solve this problem.

Video: How to Use Neem Oil For Plants

What are the Problems With Pest Control?

Part of the pest control challenge is eliminating the nasty bugs but not harming the good ones.  Your garden needs bees, ladybugs, butterflies, and earthworms.  Synthetic pesticides often create “dead zones.”  All insects (including the good ones) can’t live in these areas.   See the section “How Does Neem Oil Work?” below for why neem doesn’t cause that problem.

Another problem is that synthetic pesticides linger on fruits and vegetables for a long time, even after washing.  You can see which fruits and vegetables have the worst lingering pesticide problems by checking out The Dirty Dozen.

Since neem is a natural organic product, it won’t linger on garden crops.  It washes off in the kitchen or during rainfall.  Any remaining oil will quickly break down into simple harmless substances by exposure to sunlight.  This means neem oil will need reapplication if pest problems continue.

Continue reading to find out why pure neem oil could be the perfect solution to your garden pest problems.

What Is Neem Oil?

Oil extraction uses the seeds, leaves, fruit, and bark of the Azadirachta Indica tree (or neem tree), an evergreen native to India. People have used the oil for centuries, and it’s an essential ingredient in natural pesticides, cosmetics, moisturizers, eczema fighters, and acne washes.

It’s even helpful in removing head lice, bed bugs, or fleas from pets. The oil is less concentrated when used for skin applications than when used as a garden pesticide.

The best and strongest oil comes from the seeds.  The other parts of the plant have lower oil concentrations.  The odor of the oil is a little sulfurous, with notes of peanuts and garlic.  Pungent and interesting.  The color can range from brown to yellow to red.

The leaves contain quercetin, a well-known flavonoid and antioxidant that kills bacteria and fungi.

This remarkable oil is nontoxic to birds, mammals, bees, and plants and slightly toxic to fish.  Studies have shown no cancer or other diseases from its use.

What Types of Neem Oil are Available?

• Neem oil with azadirachtin.  This would be the 100% complete oil that comes straight from cold-pressing and filtering.
• Clarified hydrophobic extract of neem oil.  The process for this product treats ground-up neem seeds with alcohol.  This removes the azadirachtin, which is a valuable ingredient for other insecticides.  The remaining clarified oil is effective against soft-bodied insect pests like aphids, spider mites, mealy bugs, and slugs. Spraying this oil on these pests will kill them by suffocation.  It can also prevent rust, powdery mildew, and other fungal problems.

How Does Neem Oil Work?

Neem contains a powerful natural insecticide called azadirachtin and over 100 additional biologically active substances.  Azadirachtin is the main active ingredient and can kill over 200 insect pests at different stages in their life cycle.

The azadirachtin in neem oil isn’t a single chemical but a complicated structure of several compounds. There’s much scientific support for neem’s effects on insect pests, fungi, and bacteria.

Synthetic pesticides kill insects by attacking their nervous system.  This scientific approach has a problem because it causes insects to adapt and become immune to these pesticides.  Neem oil, however, acts on the hormonal system, and insect pests can’t adapt to this kind of attack.

A significant difference between insect pests and beneficial insects makes neem effective.  Insect pests kill plants by chewing them or sucking juices from the plant.  Beneficial insects will walk on plants or take nectar from the flowers, but they don’t chew on the plants or suck internal juices.

When you spray neem oil, it coats the leaves and stems, and chewing insects consume it.  The roots also absorb the oil, and the sucking insects end up consuming that oil.  Either way, it results in dead bugs.

Since beneficial insects don’t destroy plants, they aren’t affected.  Nectar doesn’t poison pollinators because neem oil doesn’t enter the process that forms nectar.  Too much neem oil inside the flowers can have an effect, however.

The oil repels other insects, and it makes an excellent mosquito repellent.  It will also kill insects that consume plant roots, such as Japanese beetle grubs and nematodes.  When insects are in the larval stage, the oil disrupts the hormonal balance.

This kills them outright or prevents them from reaching adulthood. It also immediately kills soft-bodied insects like aphids, spider mites, and slugs.

The use of neem oil protects against nearly every insect that consumes plants. It also acts as a fungicide against rust, black spot, powdery mildew, scab, root rot, anthracnose, and botrytis.

When there aren’t any fungi, there aren’t any fungal diseases.  See this article by the National Center for Biotechnology Information (NCBI).

How Does It Affect Other Beneficial Insects?

The NCBI article in the previous section mentions studies showing that neem oil isn’t harmful to earthworms.  It can benefit their growth under certain conditions.

Spiders, ladybugs, and parasitic wasps that consume insect pests aren’t affected by the oil the pests have consumed.

Does Neem Oil Kill Bees?

This is an important question that many organic gardeners are asking.  Studies were also done where they did repeat spraying of highly concentrated neem on plant flowers.

This wasn’t what would generally happen in real life, but it was the only time the oil started affecting worker bees.  This is discussed in the NCBI article.

How do I Use Neem Oil for Plants?

Test neem on your plants before a complete application.  Apply a small oil spot on the plant and check it after 24 hours.  Any damage indicates that the plant cannot tolerate the oil. Apply the oil at the base of the plant and spray it on the leaves and stems.

Neem oil has a half-life of 3 to 44 days in soil but only 48 minutes to 4 days in water.  On plant leaves, the half-life is 1 to 2.5 days.  Since this is a quick rate, apply oil often if you have a severe pest problem.

Always follow the instructions on the product you’re using.  People generally think that more of it would be better if they’re using something good.  This isn’t the case with using neem – more of it is  a waste and won’t improve the results.

A HANDY TIP – When mixing the oil with water, use castile soap or Dawn detergent.  The soap emulsifies the oil, allowing it to mix with water.  Please don’t use harsher soaps or detergents.

They contain chemicals that could harm your plants.  You could also use organic insecticidal soap as an emulsifier.

Spray neem oil starting at the bottom of the plant and working up.  Be sure to get the underside of the leaves because that’s where many pests like to do their dirty work.

To treat soil pests, pour 2 – 3 cups of oil around the base of each plant.  Do this every 2 – 3 weeks until there’s no sign of pests, fungus, or disease.

It’s essential to wear safety gear when applying neem, mainly when it’s concentrated.  The oil can irritate your skin, eyes, and lungs, but the irritation is often slight.

If you have sensitive skin, wear long sleeves and trousers, gloves, goggles, and an N95 mask to protect against any problems.

What Kind of Neem Oil Should I Use?

Make sure you buy a 100% neem oil product.  Make sure you buy a 100% neem oil product.  Some manufacturers will add harmful chemical pesticides or other ingredients.

Any of these will destroy one of the main reasons you’re trying to do organic gardening. Stay away from any products that have extra ingredients, so always check the product label.

What is Neem Cake?

After the oil is pressed, the solid residue is called neem cake.  It can improve soil by providing two key benefits:

• Pest Control.  Neem cake still has 8 – 10% of the oil, making it an effective insecticide and fungicide.  Since it’s mixed with the soil, it forms a solid defensive line against nematodes and grubs.  It also prevents fungi and bacteria from attacking the roots.⁵
• Fertilizer.  Neem cake is a valuable organic fertilizer that provides plenty of nitrogen, phosphorus, potassium (NPK), and other plant nutrients.  A substance in neem cake prevents certain bacteria from breaking down urea in the soil and releasing nitrogen gas.  If these bacteria are allowed to do this, there won’t be any nitrogen in the soil to help the plants.  Since neem cake can do this, it can enhance other organic fertilizers when they’re used.

How do I Use Neem Cake?

Apply neem cake to the soil using a mix of 5 pounds for every 100 square feet.  Mix it with the soil to a depth of about 6 inches, then water the ground very well before planting.  Store any unused neem cake in a cool, dry place.

The best time to apply neem cake is in the spring, right before planting.  Another nice thing about neem cake is its natural slow-release characteristic.  This enables it to feed and protect your plants for the entire growing season.

What Kind of Neem Cake Should I Use?

Final Thoughts

Nature provides ways to solve problems without resorting to harmful chemicals.  Reap the benefits of your work in the garden with organic neem oil and neem cake to protect it from the damage caused by pests and fungi.

Last update on 2025-08-27 / Affiliate links / Images from Amazon Product Advertising API

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