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Does using garlic as an insecticide really work? Here’s what we know

A person with green and white gloves sprays a pest control solution from a yellow spray bottle onto some roses
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Gardening is one of the best ways to take a break from daily stress and get in touch with nature. But cultivating plants sometimes leads to different kinds of stress. One of those is dealing with insect pests. Gardeners have plenty of options at their disposal, from simply letting nature run its course, to introducing predatory species that can help reduce pest pressure, to applying insecticides. When pest pressure is highest, spraying may be the only option to save the plant.

But spraying for bugs doesn’t have to mean handling toxic chemicals. Natural products, like garlic essential oil, can be helpful tools for dealing with pest pressure in a non-toxic way. If spraying plants with plant juice to save them from hungry bugs sounds like a questionable practice, keep reading. We’ll explore the effectiveness of garlic insecticide, and what pests garlic may help keep away.

Does garlic insecticide really work?

Scientific studies of garlic as an insecticide date back to the early 1970s, and anecdotal evidence goes back much further. Early research supported claims of garlic’s effectiveness as a non-toxic control for both larval and adult mosquitoes. Traditional agriculture and scientists agree that garlic can be an effective insect killer and deterrent.

Garlic essential oil, and its naturally occurring constituents diallyl disulfide and diallyl sulfide, are the keys to its effectiveness. In lab tests, these sulfur compounds interfere with the insect’s sensory receptors, causing disorientation and death at all life stages for a wide variety of flying and crawling bugs. In the garden, sensitive bugs tend to simply stay away from treated plants, but those that are present at the time of application will be killed.

What pests does garlic keep away?

The irritating and confusing sulfur compounds in garlic repel most flying and crawling insects. It’s most helpful against annoying aphids, armyworms, beetles, caterpillars, cutworms, mites, mosquitoes, and flies.

Additionally, garlic repels many larger pests as well. If you have problems with deer, mice, moles, or rabbits in the garden, a few well placed drops of garlic essential oil or a garlic based repellent may help.

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How to use garlic insecticide

Garlic insecticide is available for purchase from garden suppliers, or you can try making your own. When using a commercially available garlic insecticide, follow the manufacturer’s handling and application instructions as shown on the product label.

As a non-targeting insecticide, garlic spray also has deterrent or harmful effects on beneficial insects. For this reason it is important to use it in a way that will minimize collateral damage. For instance, do not spray if no pest insects are present or causing damage. If damaging pests are present, spray in the early morning or later in the evening when the pests are present and active. Finally, target the pest’s hiding places by spraying on the undersides of leaves and along plant stems.

Homemade garlic bug spray recipe

Materials:

  • Blender
  • Cheesecloth
  • Quart jar with a lid

Ingredients:

  • 3 garlic bulbs
  • 1 quart of water
  • Liquid dish soap

Directions:

  • Separate the garlic cloves. Leave the skins on the cloves. Discard excess wrappers.
  • Place all of the cloves into the blender and add a cup of water.
  • Put the lid on the blender and pulse until the cloves are well chopped.
  • Add the rest of the water and 4 drops of dish soap.
  • Put the lid on the blender and thoroughly liquefy the mixture.
  • Filter the mixture through the cheesecloth to remove all non-liquid particles, transferring the mixture to the quart jar.

The resulting mixture is concentrated. To use the spray, dilute 1-part concentrate with 10-parts water. Apply on or around plants with a trigger spray bottle.

The downside of using garlic

While garlic is effective against many annoying and damaging bugs, and it has no toxic effects on mammals, fish, or birds, it does present a challenge. Those with smaller yards and gardens will note the strong aroma after application. Even if that’s okay for you, your neighbors may object.

Another possible mark against garlic is that its effectiveness is reduced during rainy spells. While that’s true of any topical, non-systemic insecticide, it still bears mentioning here. If a storm is coming, it’s best to apply the treatment after the bad weather passes.

Also, as effective as garlic may be against many different kinds of bugs, some species remain out of reach. Active borers, leaf miners, ants, and other pests that live inside the plant tissue or below ground are not really susceptible to the volatile compounds due to the physical barriers involved. In these cases, other treatments would be better.

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