The Q&A Archives: Parasitic Wasps

Question: I recently noticed that tomato hornworms have just shown up on my tomato plants and read recently about parasitic wasps as a control. What should I do to encourage them?

Answer: It usually doesn't take long for beneficial insects to show up when there's a population of destructive insects in a garden. In the case of tomato hornworms, Braconid wasps are the parasitizing beneficials. It's not likely you'll see the adults, however. They are black, yellowish, or red, and 1/10 to 1/4 inch long. They lay their eggs on the bodies of hosts, such as hornworms, where the larvae feed within the hosts. The eggs look like little white rice grains attached to the caterpillar's back. To attract beneficials, try to have something blooming at all times in the garden, especially disk or ray shaped flowers. Avoid using pesticides; even organic compounds can kill beneficial species. Above all, exercise patience. The natural balance in the garden is achieved over a period of time, not overnight as many people hope! In the meantime, handpick and squish those hungry hornworms!

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