There’s a lot of talk about beneficial insects, and it can get a bit confusing. If these winged creatures are good for our garden, then of course we want them, but how do we go about it? 

What are beneficial insects?

We could define any insect as beneficial since they all serve some role in the ecosystem; however, when we talk about beneficial insects in gardening parlance, we’re referring to those that serve a helpful purpose, specifically natural pest control, for our gardens. You may also hear beneficial insects referred to as parasitic or predatory insects. 

Beneficial insects (we’ll call them beneficials sometimes for short) work in two ways: they eat the pest insect, or they are a parasite of it. Eating the problem insect is a pretty obvious solution. The beneficial feeds on the problem adult insect or often the insect’s larval stage. Parasitizing means the beneficial insect adult lays their eggs on or inside the pest insect or pest larvae. Once hatched, beneficial larvae then commonly consume the pest. 

One insect laying eggs inside another can be hard to visualize, but many parasitic insects are extremely small, sometimes an ⅛ of an inch long or smaller. A parasitic wasp can land on a prey insect, inject its eggs with a structure called an ovipositor, and fly away. 

Why do we want to attract more of them?

Using natural control methods for garden pests is an important part of an integrated pest management (IPM) approach. IPM seeks to utilize a whole-of-problem approach to pest control, including planting resistant varieties, physical and biological controls, and monitoring. Instead of the old-fashioned spray-and-pray method, IPM is a more systematic approach that is applicable to both home gardens and large agricultural producers. 

Outside our gardens (and human influence), a pest problem is soon matched by an increase in the predators of that pest. An explosion of aphids might be soon accompanied by an increase in lacewings and lady beetles, who are attracted to their food source. Human activities have disrupted this process in many ways, but we can encourage it in our gardens by creating conditions that these beneficial insects need to stay and thrive. A small effort on our part as gardeners can be rewarded with an army of beneficial insects constantly on patrol in your veggie patch or flower garden. 

Making your garden a haven for beneficials means you’ll do less work trying to protect your plants from problem insects and use fewer pesticides for a healthier and safer garden.

Common beneficial insects

Fortunately, most of us already have some beneficial insects buzzing around in our gardens, or at least in our neighborhood. Like a birdfeeder and birdbath can attract songbirds to your yard, planting species of flowers they need, and providing water and shelter will attract beneficials to hang out. Then, they’ll happily do their thing while you enjoy a cold glass of iced tea in the shade.

To list all the beneficial insects that might be found in the garden would require a book, but a few of the more commonly known and important ones are listed below.

• Lacewings are beautiful insects characterized by their large, delicate wings. They often appear green or brown, and the adults are about half an inch long. The lacewing larvae eat aphids by the hundreds with their huge jaws.

• Lady beetles (also known as ladybugs) are easily recognized, and there are dozens of species. While a few are pests that enter our homes and make a mess, most are great garden helpers. The larvae are voracious feeders of pest insects, feeding on aphids, mealybugs, and scale insects.

• Parasitic wasps are tiny, not the larger wasps that buzz around and build huge nests. They are often only a millimeter in length. They lay eggs on pest caterpillars like tomato hornworms, as well as aphids, cabbageworms, and even on stinkbug eggs. The larvae hatch and consume their host.

• Syrphid flies resemble bees as a defense against predators, but they won’t sting. Their larvae hatch and can each eat several hundred aphids. 

• Pirate bugs are less than a quarter inch long. They feed on small insects, such as mites, thrips, and aphids, by spearing them with their straw-like mouthparts. Yarrrr matey.

How to Attract More Beneficial Insects

A healthy population of beneficial insects is an excellent way to make your garden a thriving part of the ecosystem and keep pest populations at bay. Here are a few tips to help you attract beneficial insects and keep them around.

What to Plant for Beneficial Insects

Beneficial insects don’t just eat the pest insects we don’t want in our gardens. They also feed on the nectar and pollen of flowers. Because many beneficials are small, they often prefer the flatter, smaller flowers, which are gathered in large clusters called inflorescences. Queen Anne’s lace, cilantro, and yarrow are good examples. 

When planning our gardens, it’s easy to choose mostly late-summer blooming plants with big, showy flowers, but creating a space with something in bloom from early spring until frost is equally important. Not only will you have a longer season of color to enjoy, but your beneficial insects will have a habitat for the entire growing season.

The Carrot family

Plants in the carrot family are highly attractive to the small wasps (don’t worry, they’re too small to sting you) and parasitic flies, which are so helpful in the garden. While a carrot is a biennial and won’t flower until its second year, leaving a few in the corner of the garden is a great way to create a beneficial insect attractant for the next year. Other popular plantings include dill, Queen Anne’s lace, cilantro, and fennel. 

Mustards

While we typically don’t grow broccoli or mustard greens for their flowers, they will do so and become a magnet for beneficials. If you’ve forgotten to harvest a few heads of broccoli and later seen the tiny yellow blooms, you may have noticed a buzzing. Plant an extra broccoli or two (if you have room) at the edge of the garden or in a bed a dozen feet away, or let a few mustard green plants flower.

Other plants in this category include sweet alyssum, radishes (let them bolt), and bok choi.

Asters

The aster family includes some of our favorite garden flowers, so they’re easy to incorporate into your flower patch or even a deck planter. They’re attractive to lady beetles and many other beneficials. Cosmos, coneflowers (Echinacea), blanket flowers (Gaillardia), and even sunflowers are all in the aster family. 

For a cottage garden look, plant small patches of cosmos here and there in a veggie patch, although they look spectacular as a big drift of color in a wide bed. Goldenrod and Tansy are also good choices and are native in many areas. Don’t worry about the goldenrod triggering your allergies; that’s ragweed, which looks similar. 

The Verbena family

Excelling in our container gardens and hanging baskets, the verbena family also thrives in garden beds and is highly attractive to beneficial insects. Verbena and lantana are two of the most popular choices. 

Native flowers and plants

Of course, the beneficial insects that call your location home developed in conjunction with the native plants of the area. That doesn’t mean that other flowers, grasses, or shrubs aren’t helpful, but you can’t go wrong with some native selections, and they’re usually easier to grow because they’re adapted to your local weather, soil, and climate. Mixing some native flowers in with your other plantings will provide an excellent natural habitat. 

Provide Water

All creatures need water, and beneficial insects are no different. Shallow, shady watering spots are attractive to most beneficials and can be created with a plant saucer under the shade of a leaf, a small water feature in the garden, or even a muddy spot where a hose leaks. 

For best effect, place these watering spots near some other cover to provide safety from overhead predators.

Make a spot for overwintering

Many beneficials overwinter in the dead leaves and debris left on the ground in autumn. Except for diseased foliage, consider leaving the plant detritus from autumn on the ground over winter. If you can’t bear the thought of that, find a spot near the garden to leave some material for the beneficials to spend the winter in. In nature, these materials lie on the ground throughout the winter. Mimicking that process will help your beneficial insects be here next year.

Limiting insecticides

Insecticides are often indiscriminate and kill a wide variety of insects. Even those considered “safer” can still harm pollinators and beneficial insects. If your beneficial insects survive, but their prey or parasitic targets are killed by sprays, they’ll leave to find greener pastures. While that might seem okay because you’ve killed the pest insects, it means you’ll be in a cycle of always needing to spray again, exposing yourself and the landscape to harsh chemicals.

Save insecticide treatments, even neem oil and horticultural soaps, for extreme conditions where the beneficials are unlikely to gain control.