Natural Methods for Deterring Garden Pests

Pests can invade, destroy, and annoy both the garden and the gardener. While bugs are an inevitable (yet sometimes rewarding) presence in your garden, you don’t need harmful chemicals to ward off these little visitors. Many tried and true organic solutions can zap away pests without the toxic residues of chemical pesticides, which can leak into the ground and contaminate the groundwater that eventually flows from our taps. Try these organic methods to keep common garden pests out of your garden safely and naturally.

Aphids, also known as plant lice, are so common that almost every plant has one or more species that feed on it. They are small, soft-bodied insects that have needlelike mouths that suck the sap out of plants while simultaneously injecting the plant with their toxic saliva. This results in distortion and discoloration of the leaves and stem of a plant. Aphids can be brown, green, yellow, red, or black, depending on their species, but generally, you can counter all of them with the same methods. Aphids are particularly difficult to battle in that they are actually born pregnant, which means they multiply fast. To combat these critters naturally, first try to grow plants that attract predators of aphids, such as parasitic wasps (sweet alyssum, parsley, buckwheat, hairy vetch, yarrow, sunflowers and cosmos), ladybugs (dill, Queen Anne’s Lace yarrows, golden marguerite and fennel), hoverflies (tagetes), lacewings and praying mantids. Aphids also shy away from certain strongly scented plants, such as chives, basil, catnip, yarrow, and mint.

Slugs and snails are very easy to spot because of the slimy trail they leave behind. You'll usually find them on greens, such as lettuce. They usually come out overnight and hide during the day, when you'll find the evidence of their bite marks on plant leaves. There are many methods to control slugs and snails. They have very soft bellies, so an easy way to control them is to place crushed up eggshells on the ground beneath the plants they like to nibble on; these sharp edges of eggshells are like razor blades and will send them packing without killing them. Another more permanent solution is a beer trap. Place a shallow dish of beer at ground level near the plants being eaten, or create a beer funnel. (Find a 2-liter bottle with the cap. Cut it about 4 inches from the top. Dig a hole large enough for the funnel to fit (cap down) and fill it with beer at ground level.) The slugs cannot resist the beer, which they will crawl into and drown; both the slugs (and your garden) will have a happy ending. Natural enemies to slugs and snails include ground beetles, lizards, toads, and snakes to enlist their help when possible!

Rabbits may be cute, but they are notoriously persistent, sneaky, and very nimble. Just like you, they love the fruits and vegetables growing in your garden! They can burrow up to two feet into the ground to get around a fence. Your best defense against rabbits is to use fencing similar to chicken wire. Dig deep into the ground around your garden beds and place the wire fence underground and above ground. Rabbits also detest the smell of garlic so check out the recipe for the All Purpose Pesticide Spray (below).

Mosquitoes are more annoying and harmful to the gardener than the garden. When you're outside tending your garden, you don't want to get bitten. The most common ingredient in conventional bug sprays is DEET, which has linked with cancer, reproductive and developmental toxicity, rashes, and even seizures in a certain percentage of the population. Repel mosquitoes naturally with a eucalyptus-based repellent that contains the natural oil "eucalyptol." Studies have found these repellents to be highly effective, nontoxic alternatives to DEET. In addition, planting lemongrass can keep mosquitoes at bay.

Caterpillars are insatiable eating machines that can rip through your garden's bounty; but after their metamorphoses into a butterfly or moth, they become an ally, deterring pests and helping your garden. Like snails and slugs, these little critters have soft bellies that will not want to touch eggshells placed around the plant bases. You can easily remove caterpillars manually. Plucking them straight off the vine and move them to another area of the yard (away from your garden) or destroy them using one of the sprays or soaps listed below.

Leafhoppers are hard to spot but the damage they leave behind is unmistakable. They are sap-sucking insects and the plants they attack have foliage that appears crispy and burnt at the ends. To rid your garden of leafhoppers, try to attract parasitic wasps to your garden by growing thyme, sweet alyssum, dill, cilantro, parsley, yarrow, candytuft, verbena, or goldenrod. Leafhoppers also detest geraniums.

Colorado potato beetles are commonly known as potato bugs or pill bugs. Don’t let the potato in its name fool you. While potatoes are their vegetable of choice, all plants are vulnerable to their attacks, including tomatoes, eggplants, peppers and more. Deter potato beetles with strategically placed plants. They hate the scent of yarrow, catnip, and garlic.

All-Natural Recipes for Sprays and Soaps
Sometimes a gardener needs to take it up a notch with pest control, but resist the temptation to buy chemical pesticides from the nursery or home improvement store. Try the following recipes as go-to formulas for knocking out all kinds of unwanted visitors.
  • All-Natural Insecticide Soap
    The soap in this recipe gets into the skin of the insect, causing dehydration and then extermination. It is particularly helpful for soft-bodied insects. Mix no more than 1 to 2 tablespoons liquid soap (use a biodegradable, plant-based liquid soap such as Dr. Bronner's Liquid Castile Soap) and 1 quart water. Pour mixture into a spray bottle and spray pests as needed. Add this recipe to others (below) to boost its effectiveness.
  • All-Purpose Pesticide Spray
    Gather some strong scented roots and spices such as cayenne, horseradish, ginger, garlic, onions, mint, rhubarb and anything else you can think of. Boil these in enough water to cover them and let the mixture sit overnight to soak. Strain solids from the liquid and discard solids. Pour liquid in a spray bottle with some All Natural Insecticide Soap (see above). This will keep for several weeks unless frozen. Garlic Variation: Instead of using all of the other herbs listed above, simply use 1-2 heads of garlic. Deer and rabbits in particular shy away from the strong scent of garlic.
  • Caffeine Spray
    While humans tend to enjoy the burst of energy that comes from caffeine, insects, particularly aphids, do not. Gather any or all of the following herbs: yarrow, tansy, pennyroyal, thyme, lavender, rue, catnip and artemisia. Mix at least a cup of this herbal mixture with 2 tablespoons used coffee grounds and 2 cups of water. Allow this to marinate for at least 24 hours before straining and placing into a spray bottle. This can keep for several weeks.
Other Methods of Pest Control
One of the best ways to protect your garden from infestation is to grow healthy plants that are free from disease to begin with. Sickly plants make for easy targets, and while healthy plants are not defenseless, damage inflicted on them by pests will be less intrusive. So be diligent about inspecting leaves for discoloration or damage and deal with the problems as soon as possible by deadheading, pinching off, or removing entire plants that become diseased. Water your plants to their liking; protect them from malnutrition by replenishing their nutrients through organic fertilizers and compost. Keep a weed-free environment to reduce the probability of attracting pests to live among the foliage. Encourage pest-consuming predators, such as bees, wasps, lacewings, praying mantids, ladybugs, and spiders to make homes in your garden. Bees in particular are important because they destroy unwanted critters as well as pollinate your garden. Growing pollen-heavy plants will attract them to your plot.

Here is a list of common plants that attract beneficial insects:

Bee Balm
Butterfly Bush
Golden Marguerite
Hairy Vetch
Queen Anne’s Lace
Sweet William

Nature has provided many tried and true pest control methods for us. They are all "organic" and do not harm the soil, groundwater, gardener, or the food growing in your garden. Remember to exercise a reasonable amount of tolerance when it comes to pests. Allow some balance to exist between friend and foe in your garden.