Age-Old Wisdom meets Modern Tools
Beneficial Insects in the Garden
Which Insects Are Useful to Gardeners?
Here’s a short list of great beneficial insects with pictures—and with tips on attracting these good bugs to your garden.
The average backyard is home to thousands of insects. Only about a tenth of these are destructive. Most are either beneficial or harmless. Beneficials fall into three categories:
- Pollinators: we depend on these insects to pollinate our fruits and vegetables.
- Predators: they eliminate pests by eating them.
- Parasitizers: they lay their eggs on or in the bad bugs. When the eggs hatch the larvae feed on the host insects, eventually killing them.
You may have seen these good guys in your garden but were not formally introduced. Here are a few you might want to meet:
Ladybugs start out life looking like this. Did you know that a ladybug larva can eat up to 40 aphids an hour?
Adult green lacewings feed on pollen and nectar but their larvae, which look like little alligators, suck the juice from many soft-bodies insects, including caterpillars.
A praying mantis will make short work of any grasshoppers that are troubling you; these fierce predators will aso hunt many insect pests that terrorize gardens, including moths, beetles, and flies. Note too many praying mantids will turn to eating other beneficials, such as butterflies, bees, and hummingbirds—and even each other! .
Wolf spiders—though technically not insects—are often overlooked as beneficial, but they are very effective pest controllers. Since they are attracted to their prey by movement, they eat many live insects.
Ground beetles are predatory as adults and as larvae. They will eat a wide range of insects including nematodes, caterpillars, thrips, weevils, slugs, and silverfish.
Soldier beetles are an important predator of Mexican bean beetles and Colorado potato beetles. Like many beneficials, they are attracted to plants that have compound blossoms.
There is another soldier beetle called the spined soldier beetle that looks like a stink bug. I fear I may have killed more than my share of them thinking they were bad guys!
Hoverflies look like yellowjackets but don’t sting. They feed on pollen and nectar and are important pollinators. Their larvae are voracious predators, killing aphids, caterpillars, beetles, and thrips by sucking the juice from their victims.
Parasitic wasps are very tiny so you will probably not see them at work but they are very effective.
- Brachonid wasps lay their eggs on the backs of tomato hornworms, forming those white cocoons you see on the worm’s back. Leave the parasitized worms alone - the wasp larvae will take care of them for you by eating the worms from the inside out. The larvae will hatch into more wasps who will continue to do their good work in your tomato patch.
- Trichogramma wasps lay their eggs in the eggs of over 200 different insect pests preventing them from hatching. The tachinid fly looks like a small housefly but it is an active parasitizer of corn borers, gypsy moth caterpillars, grasshoppers, Japanese beetles, Mexican bean beetles, squash bugs, and green stinkbugs.
Attracting Beneficial Insects
Like all living creatures, beneficial insects have a basic need for water, food, and shelter. By providing these things, your garden will be an inviting home for them.
A diversity of plants will attract a wide range of insects. Many beneficials appear in the garden before the pests do and need alternative food sources like pollen and nectar if they are to stick around.
- Early blooming plants, especially ones with tiny blossoms like alyssum or biennials such as carrots or parsley that have been left to bloom will help draw beneficials to your yard in the spring.
- Later they will be attracted to plants with compound blossoms such as yarrow, goldenrod, and Queen Anne’s lace and flowering herbs like lavender, mint, sage, dill, fennel, and lemon balm.
Remember that if you resort to using chemical pesticides to control insects, you will kill good and bad bugs alike. Even the so-called “natural” pesticides like pyrethrum and rotenone will kill many beneficial insects.
In her book Green Thoughts Eleanor Perenyi writes, “Every insect has a mortal enemy. Cultivate that enemy and he will do your work for you.”
About This Blog
Get inspired by Robin Sweetser’s backyard gardening tips and tricks. Robin has been a contributor to The Old Farmer’s Almanac and the All-Seasons Garden Guide for many years. She and her partner Tom have a small greenhouse business and also sell plants, cut flowers, and vegetables at their local Farmer’s Market.