Pesticides have a bad reputation for harming our soil, the honeybees, and our health. It’s no wonder that more and more gardeners are choosing to grow using organic and natural methods, especially when it comes to pest and disease control. If you are one of those gardeners looking to make positive changes for your health and the environment, then neem oil is a great addition to your gardening regimen.
Neem oil is extracted from the seeds of the neem tree, Azadirachta indica, an evergreen that is native to India. Neem oil has been used for centuries in the garden, around the home, as medicine, and in beauty products. It is organic, biodegradable, and has been found to have “no unreasonable adverse effects” by the Environmental Protection Agency.
Types of Neem Oil Products
The seeds of the neem tree have high concentrations of azadirachtin, which the active chemical in the plant. However, it is important to understand the different forms of neem oil because each one has a different way of attacking pests. These different forms are a result of different processing methods.
When you extract the natural oils from the seeds you get the most complete form of neem oil. You will see this in products labeled as “cold-pressed” neem oil. Some products further process the oil by using alcohol to extract the azadirachtin. When this is done, the azadirachtin separates and you are left with clarified hydrophobic extract of neem oil.
Many neem oil products on the market will actually be this form of neem oil, without the azadirachtin, and are simply referred to as neem oil. The separated azadirachtin is the main ingredient in many commercial pesticides. You can know for sure which form you are buying by looking for the active ingredient on the label.
Clarified hydrophobic extract of neem oil works on soft-bodied insects. It blocks the pores that allow them to breathe and thus smothers them. It must make contact with the insects in order to work, so it is important to cover every surface of the plant when spraying since many pests hang out on the underside of the leaves.
It effectively treats more than 200 species of insects and works especially well with aphids, caterpillars, whiteflies, spider mites, mealy bugs, and scales. This form of neem oil is also an effective fungicide. It can prevent many fungal and bacterial diseases, including powdery mildew, rust, wilt, scab, black spot, leaf spot, and fire blight.
Azadirachtin affects insects as an insect growth regulator, anti-feedant, repellent, sterilant, and oviposition inhibitor. It works as a stomach poison and must be ingested by insects in order to work. It affects their life cycle by preventing them from transitioning into their next stage of development and laying eggs.
Azadirachtin doesn’t work as fast as synthetic pesticides, but this mechanism reduces the population of pests in your garden over time. It is most effective to use azadirachtin early in the season so that you catch pests earlier on in their life cycles when treatment is most effective.
Cold-pressed neem oil is the best of both worlds. It is pressed from the seeds and not refined any further to separate the clarified hydrophobic extract of neem oil from the azadirachtin. Cold-pressed neem oil is the most natural and complete form of neem oil, and arguably the best form to use on your plants. It has been shown to do little, if any, damage to pollinators, and it is unlikely insects will form a resistance to it due to the complexity and variety of compounds working together in the oil.
The Benefits of Neem Oil in the Garden
What’s great about using neem oil as a pesticide is that while it kills the pests that devour our garden, it doesn’t harm beneficial insects. It also encourages earthworm populations. Earthworms are extremely important to the garden, so this is a huge benefit. Earthworms tunnel through the soil, allowing oxygen to reach the roots. They also shed their castings, which are full of nutrients that enrich the soil. And when earthworms die, they feed the soil as they decompose.
Another perk of neem oil is that, unlike synthetic pesticides, you can use it up until the day of harvest. Neem oil does not harm humans or other mammals. Since it is non-toxic to us and our pets, it is the perfect treatment for houseplants. It is also useful in greenhouses, which are ideal environments for pests to thrive in if left untreated.
Neem oil is also excellent for treating your garden once everything goes dormant for the winter. Doing this will kill overwintering pests and eggs, as well as will give you a head start in your pest control efforts next spring. This strategy is especially effective for tent caterpillars, leaf rollers, aphids, and mites.
How to Use Neem Oil on Your Plants
Neem oil degrades quickly in sunlight, so regular applications are necessary. You’ll want to treat your plants every seven to 14 days when trying to eradicate pests or fungal diseases. Even if you don’t have destructive bugs in your garden, it is a good idea to use neem oil preventatively. The earlier in the life cycle you treat pests with neem oil, the more effective it is.
To make a foliar spray, mix two tablespoons of neem oil and two teaspoons of dish soap or other surfactant in one gallon of water. If the neem oil has solidified, place the bottle in warm water until it liquefies again. Spray the leaves, top and bottom, until the solution runs off the leaves. You can also spray directly on the soil to control root-knot nematodes and soil-borne diseases. When sprayed on the soil, it will also be taken up systemically by the root system, making leaves taste less appetizing to bugs looking for a snack.
While overly concentrated doses of neem oil have been shown to hurt pollinators, the bees should be okay if you use the correct dosage. Be sure to spray during the time of day when bees are not out foraging, just to be on the safe side.
Of all the pesticides on the market, neem oil has more benefits and fewer disadvantages than most others and is ideal for organic gardening. By understanding the different kinds of neem oil and how to use them, you are ready to successfully add it to your routine for a pest-free, organic garden.