Stuff You Missed in Botany: Parasitic Wasps (and other beneficial insects)

Stuff You Missed in Botany: Parasitic Wasps (and other beneficial insects)

I’ve barely been in the garden this week, but today is cool and gorgeous; so this may be a short post.

A reader wrote me to ask what a parasitic wasp was and how, as I had suggested, they could make them their friends? What a great question to answer on Botany day!

These little guys are very small, sometimes 1/100th to 3/4’s of an inch long. That’s small. So small, in fact that they often go unnoticed, to humans.

Trichogramma Wasp, Not a Mosquito

To the insects that “host” them, not so much. They are parasites in a few ways. Some of them, like the Trichogramma Wasp, lay their eggs inside the hosts eggs. The wasp embryo then eats the embryo of the host egg and hatches out. Their main diet is cutworms, hornworms, European boring worm, codling moths, and cotton boilworm to name a few. These are known to feed on 28 varieties of pests. Recent studies have found that they may help control as many as 200 pests.

How can you attract them? Well, if you’re growing things that caterpillars are going to love, chances are you’re already doing a good job of attracting them.

I grow Milkweed because I love Monarch Butterflies. If you know the botanical name, Asclepias, you shouldn’t have trouble finding it. Sometimes garden centers call it Pink Butterfly flower. I grow Common Milkweed and Swamp Milkweed. As you can imagine, if you get the Swamp cultivar, you’ll need to make sure she has water.


Other beneficial insects include Ladybirds, spiders and the KGB of beneficial insects, the Praying Mantis. They’re not so interested in Hearts and Minds, but more about breakfast, lunch and dinner.

Other than growing things to attract butterflies, which in turn attracts predatory wasps, the most important thing you can do to insure you have these beneficial insects is…

Don’t kill them!

Okay, I was trying to be witty, but what I mean is this. If you use chemical insecticides to kill garden pests, you will kill the beneficial insects that would normally feed on them as well. Don’t do it. Even some of your home brewed varieties can kill your beneficial buddies. Use sparingly. Spray cautiously. Try to target the offender only, don’t execute  the entire neighborhood to flush the creep that is eating your squash.

Plant Tansy, Marigolds, Lemon Basil, Calendula, Flax, Nasturtiums, all of these deter pests without harming beneficials.

I hope I’ve answered your questions. If not, holler back.

Have a perfectly Paisley Friday! (Yay, I get to go to the garden now!)~KeriAnne




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