Anyone who dabbles in gardening has heard about using neem oil for plants. But what exactly is neem oil, and is it safe for you and your family? How do you use it, anyway?
Neem oil is one of the most useful non-toxic tools that we have against the pests and diseases that destroy our greens. It can kill bugs like aphids and scale, as well as destroy fungi and mildew like root rot and sooty mold. At the same time, it's safe for humans and most pets and won't harm beneficial insects like bees and parasitic wasps. You can use neem oil in all areas of your garden or orchard, as well as indoors on houseplants or out in the greenhouse.
Ready to put this powerhouse to work in your garden? We'll tell you everything you need to know.
What Is Neem Oil?
Neem is an oil that comes from Indian Lilac (Azadirachta indica), which is sometimes referred to as the Neem tree. It's a common tropical evergreen that you can find growing in India and other areas of southwest Asia.
The tree produces fruit with seeds, and those seeds are pressed to get the oil, which is used in a variety of applications from cosmetics to pesticides. The primary active component is azadirachtin, but neem oil also contains healthy fatty acids and omega 3’s.
Neem oil comes in a variety of colors ranging from yellow to brown to red. It has a strong odor which is similar to garlic with sulfur overtones.
How to Use Neem Oil for Plants
The active ingredient, azadirachtin, repels insects and reduces the insect's ability to feed and develop by disrupting their hormone systems. This makes it more difficult for them to reproduce. It isn't the type of pesticide that kills bugs on contact. It works over time.
While neem oil is not a knockdown killer, it definitely should be part of your overall plan to protect your plants. You can purchase neem oil or make your own.
Look for cold-pressed, organic neem oil, because it tends to have higher levels of the active ingredients. You may also want to avoid commercial neem oil sprays because many of them contain other, less desirable ingredients. Not to worry, making your own spray is simple.
This recipe from Discover Neem works well:
- One teaspoon neem oil (use pure, cold pressed oil)
- One-third teaspoon of insecticidal soap or liquid detergent
- One quart of warm water
How To Prepare
- Mix the warm water with the soap.
- Slowly add the oil and stir to mix.
- Pour mixture into a sprayer.
- Keep shaking or otherwise agitating the mix while spraying.
Only make as much as you can use right away.
Neem Oil as a Pesticide
Neem oil for plants is perhaps most useful as a pesticide. It's a common ingredient in commercial pesticides and is found in many forms like granules, powder or liquid. Neem kills and repels about 200 kinds of pests including whiteflies, flea beetles, caterpillars, mites, and aphids.
Neem is as useful on your landscape plants and lawns as it is on veggies. Are you having a problem with Japanese beetle grubs in your grass? Spray your neem mixture on the grass and thoroughly soak bare spots.
Neem is considered safe for beneficial insect predators and pollinators like honey bees, butterflies and ladybugs.
Neem Oil As a Fungicide
Neem oil for plants also works well as a fungicide to protect them from fungi such as powdery mildew, anthracnose, leaf spot, rust, and scab.
It's particularly useful for powdery mildew, which is a common fungus that affects vegetables, fruits, and landscape trees. Like many mildews, powdery mildew likes warm, humid weather and rears its ugly head the summer months. You can spot it by the white or gray spots that appear on your plant's leaves.
Spray fruit trees and vegetables affected by powdery mildew every two weeks.
Neem Oil as a Dormant Spray
You can use neem oil for plants in your orchard as a dormant spray, which is something you spray on trees during their dormant cycle – typically in cold weather. These sprays are useful for killing overwintering insects and their eggs. Common dormant insects include mites, scale, and woolly aphids.
Neem Oil as an Organic Fruit Tree Spray
In addition to neem oil, I often use a mix containing fish emulsion and kelp as recommended by Fedco as a preventative spray during the growing season.
Apply this combination when:
- Green leaf tips emerge in spring.
- After buds first turn pink.
- Petals fall.
- About one week after the petals fall.
Finally, post-harvest, after about half the leaves have fallen from the tree, apply fish emulsion and neem oil, but leave out the kelp. Spray trees as usual, but also spray the ground to hasten leaf decomposition and kill those critters hiding in the debris.
Neem Oil as Bacteria Control
Neem will also help control bacteria issues on fruit trees such as fire blight. During the dormant period spray branches, canker areas and the trunk with neem oil.
I will admit to having an issue with fire blight in apples, particularly Honey Crisp variety. I did try neem oil as well as other organic sprays such as Serenade and sulfur. Nothing was successful, and I ended up focusing on more resistant varieties.
How To Apply Neem Oil for Plants
Neem oil for plants works best when you use it as a foliar spray. It kills pests when they eat the leaves you have sprayed. Neem biodegrades rapidly, so you may need to spray weekly to control problem species.
I recommend that you spray during times of bug activity, usually early morning or evening when they come out from their hiding places to eat.
Neem oil can kill plants if you apply it too heavily, so you may want to test it by spraying a little bit on one area and waiting 24 hours before going all in. Don't apply neem oil in direct sunlight or when temps are too hot or cold. Be particularly careful with seedlings and young plants, which are generally more sensitive than established plants.
You can also apply neem oil to the soil. The plant takes it up through its roots so when a bug takes a bite it gets a dose of the poison. This doesn't work on all plants or all pests, though, so check to see if this applies to your particular problem.
Neem has a half-life of 1-2 days on the plant and doesn't stay in the environment for long. Sunlight and microbes break it down quickly. The good news is that insects don't become immune or develop tolerance to neem oil so you can use it again and again.
Neem oil can be applied using a spray bottle, hose sprayer or watering can.
Is Neem Oil Safe?
Neem oil is not only generally safe in the garden, but it can act as a foliar fertilizer thanks to the fatty acids it contains. Some people use neem cakes as soil conditioners.
Keep in mind that though neem oil doesn't kill beneficial insects that don't feed on plants, it can harm critters like caterpillars that eat treated plants. It's safe for mammals and birds. However, tests have shown that it does cause some toxicity to fish.
So we know neem oil for plants is an excellent solution, but what about for humans? Neem oil is considered safe to use topically. One exception is pregnant women who shouldn't be exposed to neem oil during pregnancy. Don't consume neem seeds directly. They're toxic.
The FDA says that neem oil is not a recognized carcinogen in the U.S. For some people, it can be irritating to eyes and skin, so wash any produce that you've sprayed before eating it and wear gloves while applying.
In India, neem oil is used in cosmetics, soaps, and lotions. Neem oil contains carotenoids and antioxidants which are beneficial to the skin and is touted as being anti-aging and moisturizing. The oil used in cosmetics has the Azadirachtin removed which leaves it with clarified hydrophobic fatty oils. The oil can help ease the symptoms of eczema and psoriasis and be used as a hair conditioner.
What about your pets? You can use neem oil as a topical repellent for fleas and mosquitoes. It's safe for dogs and horses. However, some cats have shown an adverse reaction to neem in flea control products, so use caution.
Neem Oil Around the House
Neem oil is an effective repellent for ants, termites, and other household pests. Unfortunately, it does not have much effect on cockroaches. Control ants with neem dust. Sprinkle the powder in their pathways and around on bait food. For termites, you need to saturate the wood where they are eating using a spray.
As you can see, neem oil is handy to have around the house and garden. It's affordable, safe and easy to use – what more could you ask for?
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