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Invasive European paper wasps threaten butterflies

Many times when we are cleaning the garage, in the barn or other buildings, we find an unexpected nest of wasps.

Beware when moving items like wooden boards or anything leaning against a wall in barns, outbuildings, sheds and the like this time of year. If they have not been moved in a while, you could be in for quite a surprise.

The nests of the European paper wasps (Polists dominula) look similar to other native wasps, but you will know the difference when you see these yellow-and-black-stripped wasps heading for you. The invasive predators of butterflies were found in the 1970s in New York. Since then, they have spread out over the Northeast and the West Coast.

They are voracious eaters of caterpillars, which they hunt, kill, cut up and feed to their offspring. Who needs science fiction movies when this is happening in the insect world?

It was found in a study that the first four instars (the growth of the caterpillars to maturity) are the most hunted and killed. The fifth instar is able to thrash and move about to scare the predators away.

These wasps are smaller than our native paper wasps. They are black and yellow, slender-bodied, with the constriction or “wasp waist,” and they are distinctive with bright orange antennae. Our native paper wasps are a half inch, are more compact and have black antennae.

European paper wasps are much more aggressive. They are the dominant paper wasp in Ohio.

The fertile queen overwinters in the soil or leaf litter, and emerges to begin building her nest. It is shaped like an upside down umbrella, flat and hanging by a stem. She likes eaves of homes, under roofs, even in soil.

These wasps emerge earlier than our natives so they have the early advantage. The first brood of worker females hunt, do nest construction and colony protection, while the queen shifts her sole duty to egg laying. The adults can emerge in a little as 40 days.

Prevention is always best. Integrated pest management tells us this.

To protect your home look at eaves, attic spaces, walls, exterior lights, bird boxes, grills, etc.. You must caulk and make repairs to your home, destroy early nests and kill the queen.

If you must treat, there are pesticides labeled for treatment. Treat with spray or dust, being sure to read and follow instructions on anything you apply. It is your responsibility to properly use any pesticide in the manner as described on the label. Treat at night.

To learn more about these, go to http://go.osu.edu/paperwasp.

Hughes is an Ohio State University Mahoning County Extension Master Gardener Volunteer.

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