In our gardens we have both beneficial and harmful insects and it’s important that we differentiate between them. Indiscriminate use of a pesticide – too much, wrong material or wrong timing – can harm our garden more than help it.
Pollinators, of course, are indispensible. Other beneficial insects fall in two categories, predators like Lady Bug beetles which feed on various aphids and other small insects., and parasitoids.
Parasitoids are species whose immature stage develops on or within a single insect host, ultimately killing the host. The large green tomato hornworm caterpillar that can quickly defoliate a plant. Sometimes they appear to have many small white cocoons growing from them. That means that a tiny wasp bored into the worm’s body to lay her eggs and the larvae have been devouring the caterpillar from within. They’re getting ready to hatch and continue their beneficial work.
And then there’s the praying mantis that devour anything they encounter, good or bad, so their net contribution is probably negligible. But they’re interesting to have around so most of us call them friends, not foes.
Bottom line: gardeners should identify any insect before they take any action. A good insect identification guide is an important tool to have in the shed.
The following is a short list of beneficial insects commonly found in the garden and landscape (courtesy of NCSU.edu):
Assassin bugs prey on aphids, caterpillars, beetles, leafhoppers,and other insects. They do not like to be handled.
Big-eyed bugs attack spider mites, thrips, aphids and other insect eggs.
Damsel bugs resemble assassin bugs. They feed on aphids, leafhoppers, mites and caterpillars.
Green lacewing, or aphid lion, is known to eat as many as 600 aphids.
Ground beetles are large, dark, and sometimes metallic.They feed along the ground on soft-bodied insects, especially at night.
Lady beetle adults and larvae attack aphids, mites, insect eggs and small insects.
Micro- and mini- parasitic wasps can sting and lay eggs in caterpillars, aphids or insect eggs. The larvae consume their prey from within.
Praying mantis have a good reputation, but eat relatively few insects in the garden.
Many stink bugs are pests, but predaceous stink bugs feed on beetles and caterpillars, both as adults and colorful nymphs.
Predatory mites move rapidly to catch and feed on their plant-eating counterparts. They are often white, tan, or orange.
Soldier beetle adults resemble fireflies and are attracted to milkweed, hydrangea, and goldenrod. They eat aphids, caterpillars, mites, grasshopper eggs, and small beetles.
The harmless Syrphid fly adults resemble bees, but the small larvae consume many aphids.
Minute pirate bugs attack thrips, spider mites, aphids and small insects.
Heavily bristled Tachinid flies lay eggs on caterpillars, beetle larvae, and bugs.
Though often considered pests, these wasps and/or hornets feed heavily on caterpillars, flies, and other soft-bodied insects.
Article written by Glenn Palmer, Extension Master Gardener Volunteer.
