How to get rid of common garden pests
To protect your garden against pests it helps to know who they are, because not all bugs and insects are bad. Bees pollinate your plants, for instance, and spiders eat up several of the bugs that can spoil a garden. To help you sort it all out, I've put together a quick intro to the pests you don't want hanging around in your garden, and tips on how to keep them away. For specific guidance on how to treat pests with soap, Neem oil, and other organic repellants, read How to manage pests organically.
These bugs have piercing mouthparts that break through the surface of leaves to suck out sap or plant tissue. Some of the most destructive plants in the garden fall under this category so keep an eye out for them. Punching tiny holes through the protective layer of leaves also leaves plants open to disease. Suckers can even transmit harmful diseases to plants, much in the way a mosquito can infect our blood with malaria.
It can be hard to detect damage from sucking insects before they become a real problem. One sign they've arrived is the appearance of sticky leaves. Suckers, who are messy eaters, tend to leave syrupy drippings all over the leaves. Eventually the sugar residue grows sooty mold which looks just like somebody smeared ash all over your gorgeous plants. Another sign of trouble is yellowish, dappled leaves that eventually curl up and turn grey or black. Symptoms can also mimic drought stress, making it a challenge to know if you are dealing with pests or a lack of water.
Aphids: These minute, pear-shaped bugs come in red, yellow, green and black. They are easily identified by their long string-like antennae protruding from their head. Look for aphids on the stems of new growth or under leaves. In low numbers they're not harmful to plants. But large infestations will stress your plants, making them prone to other bug attacks or diseases.
Treatment: Insecticidal soap, attracting beneficials, spraying off with a hose
Leafhoppers: More than 20,000 different kinds of leafhoppers are sucking the life from plants all over the world. A common one, the Potato Leafhopper, is a tiny lime green bug that hides underneath plant leaves. Leafhoppers generally move in sideways steps so if you’re not sure what you’re looking at watch how it moves. To find them check the underside of leaves by gently shaking your plant to see if they leap off in surprise.
Treatment: floating row covers, DE, insecticidal soap
Thrips: Young thrips look a lot like Potato Leafhoppers to the untrained eye. A thrip is a tiny lime green bug that moves quickly. Take out a hand lens to catch a good glimpse of the bug and see if it has feathery wings. Adult thrips turn a dark brown or black. Since they only get as thick as a sewing needle they appear as tiny black slivers on plants.
Treatment: blue sticky traps for monitoring, neem, insecticidal soap
White flies: These tiny moth-like bugs with powdery white wings usually attack in large numbers. They like to gather at the tops of plants or near the ends of stems. If you can’t see them try shaking the plants and watching for a cloud of white flies.
Treatment: Yellow sticky traps, Neem, Horticultural Oils
Scale: These weird bugs are immobile and look like small oval bumps rather than insects. Their look comes from a protective covering that they secrete while feeding to stave off predators.
Treatment: Beneficial insects, Neem, Insecticidal Soap
Spider mites: Looking like miniature ticks, these pest can wreak havoc in the garden. They are so small you’ll need a hand lens to spot the colonies on the bottoms of leaves. You can also look for very fine webbing left behind in leaves after they devour it.
Treatment: Keep dust on plants to a minimum, Neem, Insecticidal Soap
Pests like beetles, caterpillars and slugs are another nuisance. While not as bad as suckers, defoliators harm plants by eating away at leaves and stems. Some eat small holes while others can consume entire leaves, leaving nothing but the veins behind. Big infestations can destroy so many leaves your plants won’t be able to photosynthesize.
Caterpillars are the larval stage of flying insects, like moths and flies. Adults lay a swath of eggs on the underside of leaves so when they hatch there's plenty of food for the larvae to enjoy. Some caterpillars, like the Cabbage Looper can eat up to three times their own body weight. They also like to build shelter around them as they feed, meticulously folding or rolling leaf edges around them for protection.
Treatment: Bt, handpicking, row covers, Trichogramma wasps to destroy eggs
Beetles: Over 12,000 kinds of beetles live in the United States. Many of them like to feast on plants. Japanese beetles will eat entire plant leaves, leaving behind only the stem, while flea beetles attack your plant by leaving hundreds of tiny holes.
Treatment: Handpicking, row covers, insecticidal soap, garlic-pepper spray, row covers, neem
Slugs and Snails: Slimy and slow, these pests are most active at night and thrive in cool, damp and shady areas where they can’t dry out. There’s almost nothing left unharmed by these squishy invertebrates as they chew large holes in leaves and destroy tender seedlings. They even love to munch on ripening fruits and vegetables, causing them to prematurely rot. Slugs and snails are not true bugs, they are actually a member of the mollusk family. Look for their slimy trail, a dead give away that they have been roaming through the garden. Watering in the morning can also reduce slug numbers because the plants have a chance to dry out before night fall. Damp plants at night, when these pest are most active tend to be devoured more easily.
Treatment: Handpicking, iron phosphate slug bait, diatomaceous earth
Animals like deer, rabbits and birds can cause a lot of damage in no time at all. I’ve even found Nimbus casually resting beneath a raspberry bush, gently plucking ripe berries for her enjoyment. Moles, voles, chipmunks, raccoons are also pests in the garden that always seem to know exactly when it’s time to harvest, often times beating you to the punch. It’s such a frustrating feeling heading out into the garden to harvest some lunch only to find that it was already eaten without you.
Treatment: Essential oils, urine, fake predators like owls or falcons, flash tape, motion sensored sprinklers, fencing, humane traps, plantskydd
NOTE: Here's additional information on how to repel pests using insecticidal soap, Neem oil, plantskydd, and other treatment options.
Acadia Tucker is a farmer in New Hampshire. Her book, Growing Perennial Foods: A field guide to raising resilient herbs, fruits, and vegetables, is available in our bookstore, as is her second book, Growing Good Food: A citizen's guide to backyard carbon farming.