Beneficial Insects in the Garden

Not all garden insects and bugs are bad. In fact, gardens rely on beneficial insects to keep the general insect population in balance. Beneficial insects are the ones that prey on or parasitize insect pests (the bad guys). You can buy many of these beneficial insects from mail-order catalogs to increase your local populations.

The average square yard of garden contains over a thousand insects. For the most part, that's a good thing. Some pollinate plants, some help break down organic matter, and some prey on other more damaging pests. Most of the insects in your gardens help — not hurt — your plants. Only a small fraction cause much damage.

Familiarize yourself with these good guys so you can encourage their presence in the garden and avoid killing them:

  • Big-eyed bug (Geocoris): These bugs dine on aphids, leafhoppers, spider mites, and some small caterpillars. Adults are tan, black, grayish-brown, or gray. They'r about 3/16th of an inch long and have large, reddish-brown eyes.

    Find big-eyed bugs on goldenrod, pigweed, or turfgrass, and relocate them.
    Find big-eyed bugs on goldenrod, pigweed, or turfgrass, and relocate them.
  • Braconid wasps: The slender adults and tiny, cream-colored grubs feed on aphids, cabbageworms, codling moths, and corn borers.

    Purchase braconid wasps from suppliers; and plant parsley-family members to help keep them around.
    Purchase braconid wasps from suppliers; and plant parsley-family members to help keep them around.
  • Centipedes: Centipedes feed on many insect pests. Although some southwestern species inflict a temporarily painful bite, none are dangerous.

  • Damsel bugs: These slender bugs prey on aphids, caterpillars, leafhoppers, and thrips. Collect them from unsprayed alfalfa fields.

  • Ground beetles: Ground beetles are large with nasty-looking mandibles. They live in the soil, where they capture and eat harmful insects. They vary in color (black, green, bronze) and in size. Ground beetles bear an unfortunate likeness to cockroaches, but the latter have longer antennae and a different overall shape. Most of the helpful ground beetles are large, dark, and fast moving. The often have nasty-looking mandibles and eyes on or near the fronts of their heads.

  • Hover flies: Adult hover flies resemble yellow jackets. They are important pollinators, while the brownish or greenish caterpillar-like larvae have an appetite for aphids, beetles, caterpillars, sawflies, and thrips.

  • Ichneumonid wasps: These wasps help you control many caterpillars and other destructive larvae. The dark-colored adult wasps vary in size from less than 1 inch to 1-1/2 inches. They have long antennae, and their long egg-laying appendages are easily mistaken for stingers.

    Adult <i>Ichneumonid</i> wasps need a steady source of nectar-bearing flowers to survive.
    Adult Ichneumonid wasps need a steady source of nectar-bearing flowers to survive.
  • Lacewings: The delicate, green or brown bodies and transparent wings of these 1/2- to 3/4-inch insects are easily recognized in the garden. Adults live on nectar, while the spindle-shaped, alligator-like, yellowish or brownish larvae feed on aphids, scale, thrips, caterpillars, and spider mites.

    To keep the welcome mat out for the adult lacewings, allow some weeds to flower nearby.
    To keep the welcome mat out for the adult lacewings, allow some weeds to flower nearby.
  • Lady beetles: Also called a lady bug, adults and larvae prey on mealybugs and spider mites.

  • Minute pirate bugs: These bugs eat thrips, corn earworms, aphids, and spider mites. You can purchase them for release.

  • Predatory mites: Predatory mites feed on thrips and pest mites.

  • Rove beetles: These beetles point their abdomens upward as they walk. They live in decaying organic, where they eat root maggot eggs, larvae, and pupae.

  • Soldier beetles: The adults are slender, flattened, 1/3- to 1/2-inch long. The larvae have the same shape and are covered with hairs. Both adults and larvae consume aphids, caterpillars, corn rootworms, cucumber beetles, and grasshopper eggs. These beetles spend much of their life in undisturbed soil.

    Soldier beetle eat aphids, caterpillars, corn rootworms, cucumber beetles, and grasshopper eggs.
    Soldier beetle eat aphids, caterpillars, corn rootworms, cucumber beetles, and grasshopper eggs.
  • Spiders: All spiders are predators. You can provide good habitat for spiders by mulching with hay and straw.

  • Spined soldier bugs: Adult spined soldier bugs dine on the larvae of Colorado potato beetles, Mexican bean beetles, sawflies, European corn borers, cabbage loopers, and tent caterpillars. Adults are tan and shield-shaped, with prominent spurs on their shoulders right behind the head.

    You can purchase adult spined soldier bugs for release in your garden.
    You can purchase adult spined soldier bugs for release in your garden.
  • Tachinid flies: These large flies feed on tent caterpillars, armyworms, corn borers, cutworms, stinkbugs, and other pests. The adult fly has a bright orange abdomen, and a black head and thorax.

  • Tiger beetles: Members of this beetle group have long legs. They feed on soil-dwelling larvae.

  • Trichogramma wasps: These parasitic wasps inject their eggs inside the eggs of more than 200 species of moths, and the developing larvae consume the host. Buy these wasps commercially.

  • Yellow jackets: These insects help rid your garden of flies, caterpillars, and grasshoppers.

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