Choose plantings that attract beneficial parasitic wasps

Tobacco hornworms

Tobacco hornworms, other caterpillars and many other pest insects are parasitized and killed by beneficial, parasitic wasps.

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Published: Thursday, March 20, 2014 at 11:59 AM.

Invisible to the naked eye, harmless to humans and a natural enemy of pest insects, parasitic wasps roam the landscape in search of an unsuspecting host in which to lay their eggs. In addition to being an important natural pest control, parasitic wasps are also necessary as pollinators in agriculture and home gardens, and often rely on the same flowering plants that attract honeybees and other pollinators. While it may sound like science fiction, parasitic wasps are real, and many are living right in your own back yard!

What are parasitic wasps?

We have all heard of parasites. Ticks, fleas, and mosquitoes likely come to mind because they parasitize humans and spread disease. Parasitic wasps do the same thing; however, they do not cause harm to humans. Instead, these wasps parasitize other insects, most of which are pests in the garden. With almost 1,900 species in North America, parasitic wasps are an abundant and vital resource, which makes them very important as a natural source of pest control.

Parasitic wasps belong to the same group of insects as predatory wasps, such as yellow jackets and hornets; however, they are much smaller. Most species of parasitic wasps are microscopic and are invisible to the naked eye; one wasp species, called the “fairy fly” is smaller than the head of a pin and depends on wind currents to fly.

Parasitic wasps are exceptionally beneficial to home gardeners because they attack many insects that plague our gardens, including caterpillars, stink bugs, aphids, and scale insects. In terms of economics, parasitic wasps save farmers and homeowners millions of dollars in chemical applications each year.

How do they control pests?

Like their predatory cousins, parasitic wasps use a stinger to paralyze their prey; however, instead of feeding on their prey, these wasps lay their eggs either on or inside a host insect. The venom of the wasp paralyzes the host, often causing it to stop feeding, which is good for your plants, but bad for the insect. Like something out of science fiction, parasitic wasps use their host as an incubation chamber. The larvae hatch and mature inside their host, feeding on nonessential fluids of its prey.

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