The Neem tree (Azadirachta indica), is native to India and over millennia its oil has acquired a multitude of uses. Neem oil is claimed to be: a natural insect repellent, a safe pesticide, a fertiliser, a skin care ingredient, a contraceptive, and a medicine with hundreds of different uses. In recent times it has become increasingly popular in Western countries. Among its many users are organic gardeners, who use neem oil for insect pest control.
How Neem Oil Works for Insect Pest Control
Neem oil is not a contact poison, as many pesticides are. It works in these ways:
- It retards growth and insects also lose the desire to feed.
- Inhibits moulting at any stage and stops larvae from developing into pupae
- If adults eat neem oil, it can affect their hormones and make them sterile or disrupt the mating process.
- Females exposed to neem oil sometimes can’t lay eggs.
- If eggs that are laid come in contact with neem oil they often don’t hatch.
- It can smother insects.
So neem works mostly by disrupting the normal feeding, growth and reproductive cycle. You will probably see live insects on your plants after you have sprayed. Don’t worry, they can’t damage your plants anymore and they can’t lay eggs on them. The spray is working.
Does Spraying With Neem Oil Harm Beneficial Insects?
After reading what neem oil can do to insects, this questions will inevitably spring to mind. The answer is: yes, spraying beneficial insects with neem oil will hurt them – the spray can’t discriminate. If it comes in contact with them directly it will do what it does to pests: it will smother them or disrupt their lifecycle.
Then why do we use such a risky pesticide?
The answer to its safe use around beneficial insects lies in the way we use it. It is vital to use the spray when beneficial insects are not around the area.
Fortunately, beneficial insects don’t stay on or around the plants for long periods of time. While pests, like aphids, live their whole lives on a plant because it provides their livelihood, beneficial insects, like bees and moths are absent from evening until after sunrise. To avoid harming beneficial insects then, it’s vital to spray in the very early morning or in the evening. Check first that there are no bees or other beneficial insects around and do a thorough spray of those insects that are sucking your rose leaves dry.
And in case you’re still worried, once the spray is dry it won’t harm the beneficial insects. They don’t chew or suck your plants.
Preparing Neem Oil Spray
I recommend that you buy a bottle of neem oil and mix your own spray. Mixing your own is not difficult and it enables you to vary the strength if that proves necessary. You also know that there are no additives. Read the instructions on the bottle and measure everything. Don’t think that a bit stronger will do a better job. The standard measurements have been tested and proved effective. “A bit stronger” might damage your plants.
The spray is a mixture of neem oil, water and some dishwashing detergent, which is added as a surfactant. Below are basic recipe and instruction for making the spray. The instructions on your bottle will probably be similar:
General Recipe for Foliar Spray
1 quart (1 litre) warm water
2 teaspoons neem oil
1 teaspoon dishwashing detergent
- Use warm water if possible and mix in the detergent.
- If you’re planning to make a large brew, first mix the full measurement of oil in a small amount of the warm water, then add that to the remainder of the water.
- Add the oils slowly, stirring vigorously.
- Now add the mixture to your sprayer.
- Keep shaking the mixture as you spray to keep it from separating.
- Use the mixture without delay – within 8 hours.
How to Use Neem Oil for Insect Pest Control
Although the spray is not toxic, it is advisable to wear protective clothing. Neem oil is not a food so it is unwise to risk breathing it in or absorbing it through your skin. If nothing else, the protective layer will keep the smell of neem off your skin and clothing.
Three ways to protect crops from insect pests using neem oil
1. Foliar Spray
This is the most common and versatile way of using neem oil for insect pest control. You can use it safely on fruit, vegetables, herbs and most ornamentals. Note, however, that neem spray can damage tender foliage, especially if it needs water. As a safeguard, water the plants a few hours before spraying.
- Spray on both sides of all the leaves. Spray the ground around the plants if you have enough spray (optional).
- When you are using the spray as a preventative measure, spray once a fortnight. You can use a half-strength solution for this.
- If you’re fighting an infestation, make the first spraying a thorough one and spray the soil around the plants as well. After that, spray weekly until the problem disappears.
- If there’s rain, you’ll need to spray again sooner.
- If there seems to be no lessening of insect numbers after several weeks, you could strengthen the concentration of the spray.
2. Ground Drench
There is very little information about using neem as a ground drench. Its effectiveness relies on neem working systemically – being taken up by the roots and working from within the plant. There is some argument about whether neem has a systemic function. The website Discovering Neem notes that neem spray or drench is taken up by the roots. Larger chewing cousins soon feel its effects but it does not reach small sucking insects.
3. Neem Oil Used in Horticultural Oils
Horticultural oils are commonly used on crops, such as fruit on fruit trees. Their purpose is to suffocate insects and larvae, and especially those that are overwintering in the trees.
You can add neem oil at the rate of 1 tablespoon to a quart (1 litre) of horticultural oil, then mix the combined oils with water according to the instructions given for the horticultural oil. The resulting spray is very effective in stopping overwintering larvae from maturing. For best results, look carefully for insects’ hiding places, such as dead branches, knots, forks or holes. Spray these thoroughly.
Neem Oil is Also AntiMicrobial
Neem oil is antimicrobial – it kills or hinders bacterial or fungal microorganisms. It will act against:
- powdery mildew
- black spot
Use it on your roses and other susceptible ornamentals
Recipe for Antimicrobial Action
2 tablespoon neem
1 tablespoon dish detergent
Follow the instructions above to mix this.
If you apply this at the first sign of trouble, the early intervention can prevent a major outbreak. Apply the spray once a week as long as the disease lasts.
Why Should I Use Neem Oil?
Neem oil is preferable to the toxic sprays you will find in gardening stores.
- Neem is safer to handle. If some touches, your skin it won’t be absorbed the way chemical sprays are. As you are probably aware your skin can absorb toxic substances just as readily as it uses the nutrients in skin preparations.
- It is more friendly to the environment. It does not leave a toxic residue.
- You can use food crops immediately after spraying if required – there is no waiting time. Any spray should be washed off before using the fruit or vegetable.
- The spray in the recommended dilution is not toxic to warm-blooded pets. That means that if your pet should come in contact with a sprayed surface there is little likelihood of harm to a healthy animal. However, garden Neem oil should never be used to treat animal parasites. Neem oil spray should be kept away from fish ponds.
- Neem spray also helps to protect plants from fungal diseases – black spot, scab, mildew etc. You can call this a bonus.
- Neem in various forms and strengths can be used for cosmetics, skin products and medicines. However, DON’T use neem spray oil for anything other than spraying a garden.
Is Neem Oil Likely to Contribute to the Development of Cancer?
No. The use of neem oil as a garden spray is unlikely to make you more prone to cancer. People have used it in many different ways since ancient times and there’s no indication that it has contributed to cancer. In fact, Scientific studies have shown that the Neem tree has therapeutic value: it’s considered a safe plant. This adds modern scientific weight to ancient discoveries.
The same studies also found that Neem is effective in preventing cancer. Can this be said of the ingredients in any of the synthetic pesticides that are sold to gardeners?
Some Precautions When Spraying with Neem Oil
- Shake the bottle well before using. Stand the bottle in warm water is the oil is too thick to handle easily.
- Spray only when the plants are shaded from the sun, such as in the early morning or late in the evening. The oil can burn tender foliage if the sun gets on it Neem is toxic to beneficial insects as well also, so avoid using it when bees are around.
- Avoid spraying in very hot or cold weather or if the plants are stressed.
- Take care to wet both sides of the leaves and any other places that insects may be hiding.
- Follow the manufacturer’s instructions.
- Don’t spray near animals or people, especially children. It won’t kill them but could cause other problems, such as allergic reactions. This is an insecticide and it should be used on garden pests only.
It is much safer to use Neem oil for insect pest control than most other commercial products offered to home gardeners. It leaves no toxic residue and, with responsible use, it is safe around warm-blooded animals. Always use it according to the manufacturer’s instructions – more is not better in this case.