Garden Insects: Friend or Foe?

Use this guide to garden insects as a tool to attract the good and repel the bad.

By Emily English


July/ August 2017

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Not all garden bugs are harmful! Many can provide pest control, pollination and more beneficial elements.

Photo by iStock; ferrantraite

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From wasps buzzing among the blooms to squash bugs decimating an entire crop, insects can be a nuisance. But before you balk at their existence, consider that, without insects, we couldn’t grow gardens at all. Indeed, the world of insects is so important, life on Earth is dependent on their existence. Still, some insects can destroy months of work overnight. Learning to tell the difference between friend and foe, and how to manage each, is vital to building a productive garden.

Friendly Fellows

Many of the insects that call our gardens home are incredibly helpful for its productivity. They increase the fertility of our soil and prey on pests that eat plants or spread disease. Encouraging the presence of the friendly insects is as fruitful as ridding our gardens of the foes.

Lady Beetles: Small, round, polka-dotted lady beetles, also known as ladybugs, love to get their mandibles on problematic aphids, mites, thrips, mealybugs and insect eggs. Although many native species of ladybugs exist, the most common lady beetle found in home gardens is the non-native Asian lady beetle, which has quickly grown in population. They tend to cluster around and in buildings as cooler temperatures arrive, and what is certainly welcome in the garden can quickly become an unwelcome pest indoors. Seal cracks and crevices around doors and windows well before fall temperatures arrive.

Big-Eyed Bugs, Stink Bugs, and Assassin Bugs: These “true bugs” all come equipped with mouthparts designed to suck the juice out of bugs and plants alike. Assassin bugs are larger than most other predatory bugs with long narrow heads, round eyes, and a long syringe-like beak. They feast on grasshoppers, flies, beetles and caterpillars. Big-eyed bugs are oval with wide, sometimes triangle-shaped heads and big bulging eyes. They prey on mites and tiny insects. Stink bugs have a shield-shaped, hard body and are green or brown. Though many stink bugs feed on plants, predatory types consume unwanted pests. Stink bugs emit a strong smell when disturbed, hence their delightful name.

Lacewings: Lacewings are slight, airy flying insects with wings that look like finely woven nets. The insects come in green (up to 1 inch) and brown (around 1/2 inch). The larvae of the lacewing, resembling tiny alligators, provide the most benefit to the garden. Voracious eaters, they devour prey by sucking out their bodily fluids.

Praying Mantids: These hulking creatures, green or brown with triangle-shaped heads and bulbous eyes, and often postured in a prayer position, will take down anything in their path, including other beneficials. Most often found in the late summer and early fall and gone by the first frost, they are kings of their domain. Impressive in stature, they conquer larger insects such as grasshoppers, crickets, flies and moths.

Flies and Wasps: Many small flying insects are ready and waiting to tackle your most unwanted creatures for you. Before swatting away that tiny wasp, consider whether it’s really out to get you or your garden’s soft-bodied insects such as aphids, thrips and young caterpillars. Unless it’s a large red wasp or yellow jacket, try leaving it be. Fly larvae eat aphids, scale insects, mealy bugs and thrips. As adults, flies and wasps often serve an important pollinator role as they search out their next meal.

Spiders and Mites: Spiders and mites should not be underestimated in their contribution to a healthy garden ecosystem. While some mites can be classified as pests, the predatory types of these nearly microscopic creatures can be helpful as they move quickly along a plant’s stem and leaves, devouring insect eggs and thrips. Spiders come in many sizes and are keen masters of ambush strategy. Both should be encouraged to live in your garden, and left alone to perform pest control.

Earthworms, Mites, and Underground Spiders: Let us also remember our friends who lie hidden under the soil. Earthworms, mites and underground spiders assist with aeration and decomposition of matter, building up topsoil and increasing soil fertility. Encourage their activity by adding organic matter, keeping tilling to a minimum, and keeping soil covered with mulch or cover crop. Soil teeming with life is a good thing — healthy soil grows healthy plants. Keeping plants healthy is the No.1 way to kick their natural defenses into high gear.

Sneaky Saboteurs

While we hope all we see in the garden are good guys, eventually we’re likely to find unwanted critters chomping on plants. Start with companion planting, trap cropping and attracting pollinators. Take daily walks through the garden to pick off invaders and drop them into soapy water. Follow with a DIY repellent spray below, and you should be on your way to a balanced, thriving garden.

When you see bugs you don’t recognize, first identify them to determine the best method for handling them. For more identification help, visit the Pest Management link on North Carolina State’s extension website: growing small farms.org. We never recommend the use of non-organic chemical pesticides, which indiscriminately kill beneficial and harmful bugs.

Squash Bugs: Squash bugs are the bane of every squash grower’s existence. Adult and nymph bugs suck plant juices from the leaves of squash and pumpkins, causing them to wilt, blacken and die. Squash bug adults are about 5/8 -inch-long with a hard-shelled body. Eggs can be found on the underside of leaves in clusters of about a dozen. Hatching in 10 to 14 days, the nymphs change from bright orange to gray. Manually ridding plants of squash bugs and eggs is the most tried-and-true method. Examine plants frequently, squish eggs and drop bugs into a bucket of soapy water. If eggs prove difficult to detach, trim off the parts of the leaves where the clusters are attached.

Aphids: Small, pear-shaped bugs that look fluffy as they scurry around stems and leaves, aphids suck juices from leaves, leaving them curly and dying. A strong blast from the hose will drown them; sunflowers can draw them away from vegetables; and a strong garlic or rosemary spray may repel them.

Stink Bugs: The southern green bug leaves yellow, calloused blotches on tomatoes and can affect their flavor. Control them with strong-smelling sprays and oils — garlic, mint, lemon verbena, oregano and thyme offer success.

Cucumber Bugs: Similar-looking to ladybugs but yellow and black and narrower, these beasts attack cucumbers, squash, melons, eggplants and cabbages. Protect plants with garlic and chili pepper spray, and consider row covers for young plants.

Squash Vine Borers: Squash vine borer larvae destroy the inside of the stem, killing plants rapidly. Grow squash and pumpkins under row covers until they bloom, then protect exposed lower stems with masking tape. Use tape to remove any eggs on plant stems. If you see moths near plants in the early evening, kill them with a fly swatter or by spraying with hairspray (this makes them unable to fly, then you can kill them). Every moth can lay more than 150 eggs, so killing even a few is worthwhile. If you see holes in stems with insect excrement nearby, borers have made their way into the stem. Use a sharp knife to make a slit in the stem near the hole, and tweezers to remove borers (there may be one or two). Patch the hole with mulch. If you have plants to spare, pull up infested plants. Chickens are helpful in managing squash vine borers.

Flea Beetle: Flea beetles are black, jumping beetles about the size of fleas. Symptoms of flea beetles are tiny holes in leaves that can ultimately cause irreparable damage. They are particularly hard on broccoli, Napa cabbage and eggplants and can also attack young tomato and pepper seedlings. Interplanting radishes has shown some success, as well as planting a trap crop of mustard around the border of your garden. Avoid planting trap crops close to other plants they love. The odor of onion plants or garlic is recommended as a repellent. These are also easy to grab and squish by hand.

Cabbage Looper Worms: These green caterpillars will eat large holes through cabbage and collards. Look for light green eggs and worms on the underside of leaves. Pick loopers by hand and repel future visitors with garlic and chili pepper.

Colorado Potato Beetle : Left unchecked, the Colorado potato beetle can decimate potato crops. It also feeds on tomatoes, eggplants and peppers. The large, tan beetles with black stripes overwinter in soil and emerge in spring ready to lay clumps of eggs on the undersides of potato leaves. Check leaves daily for infestations and physically remove eggs, larvae and beetles. Some evidence suggests that herbs such as catnip and sage, and extracts such as citrus oils, can deter this aggressive beetle.

Tomato Hornworms: These monster green caterpillars are beautiful with slanted stripes, dark spots and a big thorn on their rear, but overnight they’ll eat leaves and stems right off of tomato plants, leaving behind telltale large black droppings. Pick them off and drop in soapy water or feed them to chickens. Interplant dill, basil and marigolds with tomatoes, and keep parasitic wasps around for tackling these creatures.


Plants to Attract Friends

Gardening information sources will turn up a dizzying array of plants that attract beneficial insects. Most of these plants will attract a number of beneficials. Here is a partial list of some of the best choices. Intersperse them among your garden beds to help draw in the bugs best suited to defending your crops.

• Caraway
• Clover
• Coreopsis
• Coriander
• Cosmos
• Dill
• Fennel
• Lemon balm
• Marigolds
• Mustards
• Queen Anne’s lace
• Sunflower
• Tansy
• Yarrow


Encourage Beneficials

• Dedicate 5 to 10 percent of your garden space to crops that attract beneficial. Find an extensive list at Permaculture Research Institute.
• Never spray broad-spectrum insecticides, which kill both friends and foes, near your garden. Even organic pesticides can kill beneficial insects. If you use one (even DIY), target the most ailing plants and avoid spraying plants in bloom.
• It’s OK to leave some pests, which are food for the beneficials.

For DIY Repellents visit:
4 DIY Insect Repellents