Photo courtesy: Washington State Department of Agriculture

If you think you’re seeing more wasps than usual this year, you’re probably seeing a critter we inherited recently from Europe, the European paperwasp.

The European paperwasp Polistes dominulus was first recorded in the U.S. in Massachusetts in 1981 and has moved its way West since then, reaching Washington State in 1998. As Keith Seinfeld, KPLU News Seattle, reported in 2006, “So far there’s no sign of environmental damage done by the European wasps and it’s not particularly aggressive, in fact it may do a little good in the garden by eating other pests.”

These paperwasps are often confused with yellowjackets, another kind of wasp, because they have similar markings. The easiest way to tell the difference between the two is their nesting habits. European Paperwasps create nests that are only one cell deep forming a single comb and resembling a Dixie cup-sized upside down umbrella. Yellowjackets create large aerial nests that are entirely enclosed in paper. Yellowjackets will also construct nests below the soil surface.

Fortunately, there are some good things about both the European paperwasp and yellowjackets: wasps eat flies, aphids, caterpillars and other invertebrates making them an important insect-controlling predator. “We would have serious pest problems if it weren’t for yellowjackets,” says Todd Murray, an entomologist from Washington State University’s Extension program. In fact, yellowjackets are used as biological control agents in corn, cotton and tobacco crops. A few well-placed nests can clean acres of crops of any pests. It’s the wasp larvae that feed on other insects, supplied to them by adults. Adults feed on nectar, pollen, fallen fruit and other dead insects.

So far, the European paperwasp has been described as docile in the Pacific Northwest. Murray says that from what he’s witnessed the wasps are only concerned about maintaining their nests. “While photographing a queen, I bumped her with the camera lens. She just shot me a dirty look and went back to work,” says Murray. “Rarely do I see aggression when I’m present around their nests.”

European paperwasps like to build nests on human structures like roof eaves, decks, overhangs, doorways, outdoor light fixtures, BBQ grills, birdhouses, mailboxes – and pipe coral fencing along horse paddocks. Murray recommends that when possible leave the nests alone. You may actually benefit by having them around to feed on barn and garden pests. But remember, unlike bees, wasps can sting you as many times as they want and some people can react very violently and undergo anaphylactic shock as an allergic reaction.

Prevention is key for keeping wasps out of wall voids, attic spaces, tack rooms and barns. Seal any cracks, gaps and holes to prevent wasps from entering and setting up shop. For air vents, install small-sized wire screen to prevent wasps and other critters from entering. If you must remove a nest, contact your local extension office for more information on the best way to go about it--some people can be highly allergic to wasp venom.

And one more thought: Fall is the time when all wasps are most prevalent. By the end of summer nests are at maximum capacity, which means lots of adults are around with fewer larvae to care for. Plus, in autumn the wasp’s nest is about to be abandoned and adult wasps are reaching the end of their life cycle. So beware of these flying insects when trail riding with your horse.

Trail riding rules and wasps

My rules for end-of-summer trail rides in areas where ground-dwelling yellowjackets are more active are:
1) Make sure all riders in your party are aware of the risks and nature of ground-dwelling yellow jackets.
2) Find out ahead of time whether any member of the party is allergic to wasp stings. If so, determine if they carry an EppiPen kit.
3) While riding in a line, the #2 and #3 riders have a particular responsibility to watch for angry wasp activity. Ground-dwelling wasps are usually stirred up by the first rider who doesn’t see them, then the angry insects inflict their punishment on the remaining riders in line.
4) If anyone spots wasp activity we yell “BEES” (much easier to yell than “wasps”) and we RUN!  Horses stung by wasps often want to stand in the same spot and rub off the stinging insects; bad idea when the rest of the angry hoard is still piling out of the nest. You may have to kick hard to get your horse to move quickly from the area but it is imperative for your safety and that of others that you do so.
5) After you are well away from the area then it is safe to dismount and inspect your horse, riders and dogs for possible stings.

Treating wasp stings on horses

A few stings on your horse’s body can be soothed with a cold water hosing and perhaps something like aloe vera gel. If your horse experiences excessive swelling, irritability, pain or difficulty breathing contract your veterinarian immediately. Stings on your horses’s head, muzzle or other sensitive areas need to be watched very closely for signs of excessive swelling or other serious problems. 

For more information on how to be prepared for wasps and yellowjackets on your trail rides and what to do if your horse gets stung, check out Bee Prepared in The Horse.

For help in identifying the two wasps and more on European paperwasps see this article by Washington State University, Garden Friends and Foes, European Paperwasps.

Bee safe!