Beneficial Insect: Parasitic Wasp

These tiny, non-stinging wasps are some of the most beneficial insects in the garden and are known to parasitize over 200 species of pests. Though there are tons of different species of parasitic wasps, they all work by preying upon one or more pest insects.

Parasitic wasps generally measure between 1/32”-1/2”, though a few are larger. They have slender, elongated antennae and are found throughout the U.S.

Life Cycle

Most female parasitic wasps lay eggs inside or on host insects (though some may also lay eggs inside prey eggs). The wasp eggs hatch and consume the prey, beginning with non-essential tissue first, then proceeding to vital organs- eventually killing the host. Some species then pupate in external cocoons, which remain attached to the host’s body. Other species pupate within the prey and emerge as adults. Most species have a high reproductive capacity and develop rapidly.

Pests They Control

Depending on the species of parasitic wasp, they help rid your garden of: aphids, beetle larvae, bagworms, cabbage worms, Colorado potato beetle, corn ear worms, cucumber beetles, cutworms, gypsy moth caterpillars, Japanese beetles, leaf-miners, mealybugs, Mexican bean beetles, moth caterpillars, sawfly larvae, scale, squash vine borers, tent caterpillars, tobacco budworm, tomato hornworm and whiteflies. Wow!

How to Attract and Keep Them

  • Provide them a diversity of plants with single blossomed flowers and flowering herbs since they consume nectar and pollen. This will help welcome them to your garden. Choose: allium, alyssum, cosmos, dill, fennel, lemon balm, thyme, statice, yarrow and zinnia.
  • Purchase parasitic wasps and release them into your garden. Their eggs usually arrive on cards containing anywhere from several hundred to several thousand eggs. The cards are then placed in the garden or greenhouse, where they will hatch.

More About…

Technically speaking, ‘Parasitic Wasps’ are not actually parasites - they are parasitoids. This is because a true parasite is something that lives at the expense of its host but doesn’t actually kill it, whereas parasitoids nearly always kill their host. In general though most people still use the term ‘Parasitic Wasps’.


CCF staff
Good Bug, Bad Bug by Walliser 2008
The Organic Gardener’s Handbook by Ellis and Bradley 1996

Gardening Tips Pests beneficial insects bugs insects organic pesticides

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