Parasitic wasps important biological control

Q. I found some small flying things on my window sill. Can you identify them? I will bring in a sample.

Linda from Austintown

A. Linda, thank you for contacting the OSU Extension office clinic and for bringing in a sample! Samples always help clarify what the insect is and help us determine whether you need to do anything about it.

After quite a bit of research your sample was identified as one of the Chalcid parasitic wasps. These are one of numerous parasitic wasps families found in the insect order Hymenoptera which includes other wasps and bees. Parasitic wasps make up one of the most important biological controls in the home garden, getting rid of unwanted insects the natural way.

These wasps attack a wide range of hosts, laying their eggs either within or on the host’s body or eggs. As the wasp’s eggs hatch, they develop and feed upon and kill the host (mostly soft bodied insects that harm your plants!)

Among the wasp’s hosts/victims are many types of caterpillars, aphids, beetles, bugs and other pests that can bring havoc to everything from cabbage and tomato plants to the leaves of sunflowers and zinnias.

Parasitoid wasps are very diverse in appearance, ranging in size from as small as a fleck of pepper to nearly 3 inches long and from uniformly dark in color to brightly colored and patterned. Under the microscope, the iridescent wings are quite a sight to behold.

And while these wasps are tiny agents of death for their victims, they do not sting people.

There are thousands of species of parasitic wasps, but they mostly go unseen because of their size and life cycle. An observant gardener may see adult wasps around flowers because the adults of some species feed on nectar.

Sometimes you may see a tomato hornworm caterpillar which looks like it has tiny white seeds on its back. This caterpillar has been parasitized by a wasp and will soon die.

The white seeds are the pupal capsules about to release another generation of parasitic wasps into the environment.

Parasitic wasps are considered beneficial insects and no control is recommended. The wasps are very sensitive to insecticides, so avoid or limit the use of chemical sprays. These wasps are your ally in the fight against pests.

So how did this tiny wasp get into Linda’s home? We occasionally get reports of these showing up in people’s homes because a caterpillar, cricket or some other insect that was parasitized came inside, died and the parasites eventually emerged. A lone cricket can have hundreds of these emerge from it!

For more information on parasitic wasps, see http://go.osu.edu/goodwasps .

Today’s answer is provided by David Sprague, OSU Extension master gardener volunteer. Call the office hotline at 330-533-5538 to submit your questions. Regular clinic hours are 9 a.m. to noon Mondays and Thursdays.