The Best Ways to Use Garlic for Pest Control in the Garden

I don’t think I’ve experienced a single day without having garlic in my house. I toss it into pretty much every savory dish I prepare, and it’s astonishingly medicinal too. That makes it invaluable to any household. But did you know that you can also use garlic for pest control in the garden?

It’s true! Garlic is a startlingly effective pesticide and fungicide and has multiple uses on the homestead. There are even scientific studies to back up what many gardeners have known for centuries.

Read on to learn how you can put garlic (Allium sativum) to use for your own garden needs.

Which Pests Can be Controlled with Garlic?

Garlic’s sulfurous compounds are what make it so pungently burning when you bite into it. Few people can nibble raw garlic without wincing, and it has a similar effect on other mammals and insects alike.

The active compounds found in garlic include diallyl disulfide, dimethyl trisulfide, and diallyl tetrasulfide. These compounds are repellant to many insect pests but are also toxic—even fatal—to others.

Some of the animal and insect species that garlic can repel include:

• Aphids
• Ants
• Armyworms
• Beetles (including flea beetles)
• Cabbage flies (adults and eggs, not larvae)
• Caterpillars
• Cutworms
• Deer
• Fruit flies
• Gall midges (adults and eggs, not larvae)
• Groundhogs/marmots
• Grubs
• Mice
• Moles
• Moths
• Rabbits: warning! Garlic can kill pet rabbits if ingested
• Root borers
• Slugs
• Snails
• Spider mites
• Spined soldier bugs: potentially fatal reaction
• Squirrels
• Termites
• Vine borers
• Weevils
• Whiteflies
• Yellow mealworms (and their larvae): potentially fatal reaction

The methods for repelling these species can differ, but we’ll go into that a bit further down in this article.

What About Pathogens?

Absolutely yes. Garlic’s natural fungicidal properties are what make it so effective for treating conditions such as athlete’s foot and candida in humans. As such, it can also be used to treat outdoor fungal pathogens—particularly those that like to sit in the soil and wait for potential victims.

In addition to treating soil against damping-off disease, I’ve used garlic-infused water to treat powdery mildew, downy mildew, and rust on various species.

Is Garlic Potentially Harmful to Plants or Pets?

The short answer here is “no,” but there are some aspects that you should keep in mind.

Since garlic is organic, and you’re diluting the juice quite a bit, it’s unlikely that it’ll cause your plants any harm when used as a pesticide or fungicide.

The main issues that can occur would be if you sprayed down your plants at the hottest part of the day. The water droplets on leaves and stems can act as mini magnifying glasses for the sun. As a result, your plants can get some nasty burns.

If you’re treating your plants for insect pests or fungal issues, then spray them early in the morning before the sun reaches its zenith. This way, excess moisture has time to evaporate before they have a chance to burn.

As for pets, nearly all animals avoid garlic whenever possible. They generally can’t stand the scent of it, but the spray won’t harm them. Thankfully, most avoid ingesting it as well.

The one type of pet that’s vulnerable to garlic is a pet rabbit. Alliums such as garlic and onions can be immunosuppressant to bunnies, and that can cause an anaphylactic reaction. Fortunately, they generally can’t stand the smell and tend to stay as far away from it as possible.

As far as plant health goes, keep in mind that just like garlic has good neighbors, it also has poor ones. If you’re planning to use garlic for pest control, make sure that you’re not intercropping it with incompatible species.

For example, garlic can stunt growth in carrots, peas, beans, parsley, and asparagus. Furthermore, it doesn’t like to be planted near any other alliums, including onions, shallots, chives, and scallions. This is because alliums compete for nutrients and don’t play nicely together at all.

What Type of Garlic to Use

The best garlic cultivars to use are the ones that are the most potent. By this, we mean those that have the strongest, most fiery flavor; the kind that makes your mouth burn and your eyes tear up if you taste it. Since you’re using garlic for pest control, diffusing its oils and scent around an area, you’ll want to aim for powerful potency.

Bogatyr garlic is colloquially known as “Russian penicillin,” as its powerful compounds are excellent for fighting off all manner of health issues. Behind that are Siberian and Red Donetsk (Ukrainian) varieties. Basically, if it originated in Eastern Europe, you’ll know that its strong Slavic genes will beat down whatever pests you’re fighting.

Methods for Using Garlic for Pest Control

You can use garlic for pest control in a few different ways. These will depend on what kinds of pests or pathogens you’re dealing with. In addition, you can often combine techniques to double down on your pest-kicking.

Think of this as treating an infected wound with both oral/internal medicine and a topical poultice. If you treat an issue with two complimentary approaches, they often meet in the middle to ideal effect.

Companion Planting/Intercropping

Many people plant garlic in and around their crops as beneficial companion plants.

For example, garlic can be exceptionally helpful when planted around fruit trees at the dripline border. Herbivores such as deer hate its scent and will avoid stepping on or across it to get to the tasty tree. The same goes for squirrels that would otherwise try to get to your crop before you can.

Garlic is also a great companion plant for tomatoes, eggplant, peppers, cabbage, kale, broccoli, cauliflower, Brussels sprouts, kohlrabi, and beets. It can help to fend off cabbage white butterflies, nightshade hornworms, aphids, and various other pests from these plants.

Foliar Spray

To make a foliar spray, you can brew up a nice batch of garlic water and hose affected plants with it.

If you have a juicer, grab a couple of bulbs of garlic and peel the cloves. Then put them through the juicer with a couple of spoonfuls of water until you have a 1/2 cup of concentrated garlic juice.

Otherwise, you can either mash them with a mortar and pestle or put them through the blender with a bit more water.

Mix 1 tbsp of concentrated garlic juice with 3 cups of water, and decant that into a spray bottle. Then hose down the affected plants as needed. I find that cackling and swearing at the insects I’m spraying is immensely cathartic, and may even help the spray’s effectiveness.

Topical Soil Treatment

Cutworms have been the bane of my gardening existence here in the Laurentides. They’ve cut down my corn and amaranth repeatedly and generally wreaked havoc on anything I’ve tried to plant.

I’ve used garlic for pest control to deal with these jerks to good effect when I haven’t had the time or patience to wrap individual stems with cardboard to save them.

Mince or crush a handful of fresh garlic cloves and then sprinkle them on the soil around affected areas. The scent should fend off crawling interlopers such as beetles, slugs, cutworms, and ants rather effectively.

I’ve also used garlic powder to fairly good effect here. This method only works temporarily, however: garlic powder washes away easily via rain or regular watering. As a result, the effect from minced or chopped fresh garlic is longer-lasting, and also more powerful/pungent than its powdery counterpart.

Additionally, if you find mole holes anywhere in your garden, cram some chopped garlic cloves into them. Moles hate the scent so much that they’ll find a different place to live, now that you’ve befouled their hallway.

Soil Soak

I’ve used this method (also known as a “drench”) to treat soil that had previously caused damping-off disease in some of my seedlings. The process involves brewing up a large quantity of the aforementioned concentrated garlic juice, and mixing it with water.

The ratio I use to treat soil is 1 cup of garlic juice to 4 gallons of water, but you can dilute it further if preferred. If you’d like to ease into this, then use a 1/2 cup of garlic juice instead.

Turn the soil over or perforate it well with a pitchfork. Then pour this liquid liberally over the affected area and allow it to soak in. Repeat the process daily for at least a week, then let the area dry out well, if possible.

As an added bonus, this soak can kill off grubs that may be lurking in the soil. If your lawn has unexplained yellow patches, dig up one of the areas and look for grubs. Should you find any, offer them the garlic soak treatment mentioned above.

Put Garlic to Work in Your Garden

As you can see, garlic isn’t just an invaluable plant-based medicine for humans, but also works wonders for garden plants and crops!

Be sure to keep some potent raw cultivars around at all times just in case you need them, and when you do need them, act quickly.

The sooner you use garlic for pest control—whether against interlopers or fungus—the greater your chances of catching the issue before it spins out of control.