Insect allies: predators and parasitoids in the garden

It’s important to identify an insect in your garden before taking action. Are you sure it’s a “bad guy?”

Many insects are actually providing free pest management!

Natural enemies, insects that kill or suppress other insects, help control prey populations and keep nature in balance. There are two categories of natural enemies. A predator is an insect that captures and eats another insect (the prey). A parasitoid is an insect that develops on or inside another insect (the host). The host usually dies in the process of the parasitoid’s development.

Conserving Natural Enemies

Natural enemies need alternate food sources in addition to prey. While they’re out hunting, insect predators might need “snacks” to keep up their energy. Cue flowering plants! Flowers provide nectar and pollen that natural enemies use as supplemental food while hunting or if prey becomes scarce.

To keep natural enemies in the area, plant flowers with varying bloom times, providing food year-round. Native plants are especially pest-tolerant and supportive to natural enemies. Bonus: While drinking nectar and traveling between flowers, natural enemies become pollinators!

Natural enemies also need habitat where they can reproduce, take shelter and overwinter. Aim for structural complexity— variation in height, depth and texture—in your plantings to provide plenty of cover. Many overwinter in cavities, twigs and leaf litter, so “leave the leaves” where you can.

Some natural enemies, like lady beetles, can be purchased in bulk for release in the landscape. This is a short-term solution. The most sustainable way to reap the benefits of our insect allies is to attract and retain them with suitable habitat and food sources. It’s important to remember, natural enemies need prey! Don’t expect to eradicate all pests. It is impossible, and you will lose your natural enemies. Instead, aim to keep pest populations at tolerable levels.

Common natural enemies

Wasps

Most wasps are predators—they capture insects to feed to their larvae (immature wasps). Social wasps, like paper wasps and yellowjackets, live in colonies. Social wasps can be aggressive when their nests are disturbed but are generally docile while they are feeding on nectar. Many are generalist predators, eating a wide variety of different insects. Caterpillars, including corn earworms, armyworms, loopers and hornworms, are popular prey. Solitary wasps do not live in colonies. A female solitary wasp creates one or a few nests at a time for her developing larvae. She may build her nest in the soil, in a cavity or with mud. After she lays her egg inside, she hunts and delivers live (sometimes paralyzed) prey to her hungry larva once it hatches. Solitary wasps are rarely aggressive.

Parasitoid wasps are extremely beneficial and come in all sizes, from nearly microscopic “fairyflies” (0.5 mm) to giant ichneumon wasps (up to 5 inches). Most lay eggs directly inside aphids, whiteflies, scale insects, leafminers or caterpillars. The larvae hatch and feed inside the insect until they are ready to pupate, emerge as adults and fly away. Gruesome but cool!

Beetles

Lady beetles, or lady bugs, come in all sizes and colors, not only red with black spots. Adults and larvae eat a variety of garden pests, like aphids, mealybugs and whiteflies. Some larvae can consume 200500 aphids before they reach adulthood! Beetles in the family Carabidae, called ground beetles, are common in the garden. These generalists have long legs and powerful mandibles for chomping prey. Adults and larvae are often found hunting on or in the soil at night.

True Bugs

Insects in the order Hemiptera are known as “true bugs.” Some of our worst garden pests, including aphids, whiteflies and scales, and some of our most valuable predators, are true bugs.

Insects in the genus Orius are called minute pirate bugs for their diminutive size (2-5 mm) and are predators of aphids, armyworms, thrips, spider mites and whiteflies. They can even deliver a pinch to unsuspecting humans. Assassin bug adults and nymphs (immature true bugs) use sharp beaks to pierce aphids, leafhoppers, caterpillars and Japanese beetles. Larger assassin bugs, like the wheel bug, should be handled with caution or not at all, as they can administer a powerful bite.

Flies

Hover flies and flower flies are predators of common garden pests, including aphids. Many species mimic wasps and bees but cannot sting. Robber flies are aerial predators of many insects, including other predators! Larvae feed on soft-bodied insects, like scales and mealybugs.

Flies in the family Tachinidae are parasitoids. Females lay eggs in or on host grasshoppers, Japanese beetles and stink bugs. Larvae feed on the host, leading to its demise.

Lacewings

Lacewings eat soft-bodied mites, aphids, mealybugs and scales. Look out for lacewings’ distinctive eggs, which are perched at the ends of long, graceful stalks.

You may also see mantids, or “praying mantises.” These insects are powerful ambush predators that capture a variety of different insects. Dragonflies may be in the garden if a pond or body of water is nearby. Dragonflies have excellent eyesight and can move each of their four wings independent- ly, making them precise aerial hunters. They especially like mosquitoes and have earned the nickname “mosquito hawks.”

While spiders are arachnids, not insects, they are excellent predators that feed on a wide range of pests. Garden spiders build webs to capture their prey, while jumping spiders and green lynx spiders are ambush predators that pounce on unsuspecting insects.

Natural enemies are our allies in the garden, providing valuable pest control services and enhancing the complexity and wonder of our natural world. Next time you’re out in the garden, look closer. Is that a foe you see, or could it be a friend?

If you are interested in learning more about common insect predators in the garden and easy ways we can conserve them, please join me for a virtual talk on Sunday, March 19 at 2 p.m. To assure your place in the third class of the Spring 2023 Gardening Lecture Series presented by the North Fulton Master Gardeners, “Insect Allies: Predators and Parasitoids in the Garden,” please register at https://bit.ly/Spring2023NFMG-GardeningLectureSeries. The class will also be available for later viewing on the NFMG YouTube channel at youtube. com/northfultonmastergardeners.

Happy Gardening!

North Fulton Master Gardeners, Inc. is a Georgia nonprofit 501(c)(3) organization whose purpose is to educate its members and the public in the areas of horticulture and ecology in order to promote and foster community enrichment. Master Gardener Volunteers are trained and certified by The University of Georgia Cooperative Extension. Learn more at nfmg.net.

About the Author

This week’s guest Master Gardener columnist is Gabrielle LaTora, agriculture agent in Fulton County’s Extension office. An entomologist by training, Gabrielle is interested in insects on farms and in gardens and is passionate about closing the gap between people and their food. In addition to helping coordinate Fulton’s Master Gardener Extension Volunteer program, Gabrielle oversees the North Fulton Community Garden, answers clients’ questions about gardening and natural resources, works with urban farmers and delivers high-quality educational programs for Fulton County residents.