Garden Tips: Yellowjacket or paper wasp, a case of mistaken identity

Several years ago, I mentioned a brand of wasp traps called WHY were excellent for trapping yellowjackets.

These devices are baited with a chemical lure developed by Dr. Peter Landolt, a United States Department of Agriculture entomologist in Wapato. Landolt recommends putting up traps baited with fresh lure in late March to mid-April to catch overwintering yellowjacket queens before they start new nests. However, if you have used these traps and failed to catch any yellowjackets, you may have mistakenly identified look-a-like paper wasps as yellowjackets.

The European paper wasp is a non-native wasp that looks paper much like the common yellowjackets found in our area. This wasp has become a nuisance in our region. It is identified by its long yellow hind legs that dangle during flight, and by its bright orange antennae. While European paper wasps could be considered beneficial because they feed on garden insects, their predisposition to aggressively protect their nests makes them a nasty stinging pest.

European paper wasps are relatively new to the U.S. They were first discovered in the U.S. in the 1970s in Massachusetts. Since then, they have spread across the northern part of the country, reaching Utah in 1995 and Colorado, California and Washington sometime between 2001-03. Like other types of paper wasps, they also build papery nests. Their nests are open and shaped like upside down umbrellas. These nests typically do not grow extremely large, containing less than 50 adults by the end of the summer.

European paper wasps find their nests almost anywhere that they can find a small, dark cavity or void. Favored sites are under house eaves and overhangs, deck flooring, lighting fixtures and grills. Because of their aggressive behavior when defending nests, discourage their nest building in gardens and near homes.

Unfortunately, the bright yellow commercial yellowjacket and wasp traps, including WHY traps, do not attract European paper wasps. Our best bet is to look for these leg-danglers at this time of year and note where they are taking up residence. Once you find the relatively small early nests, dispatch adults and their nests with great care.

Use a pressurized wasp-yellowjacket spray to kill the adult wasps. These aerosols allow you to stay a considerable distance away from a target while spraying. Spraying should be done during the cool of the day at dusk or dawn, when the adults are less active and in the nest. As always, when using a pesticide product, read and follow the directions. Hire a professional if you are allergic to wasps.

Once you are certain all the adult wasps are dead, remove and destroy the papery nest, because it may still contain larvae that were not killed by the spray. Afterward, clean the nest area with water to remove lingering wasp odors that could attract surviving adults.

Landolt is trying to develop a commercial chemical lure that will attract European paper wasps, but until that happens, carefully destroy nests or make your own trap. Landolt’s research has revealed that these wasps are attracted to fermenting fruit. For instructions on building a trap, go to Utah Pest News here.

This story was originally published April 10, 2016 at 9:48 AM with the headline "Garden Tips: Yellowjacket or paper wasp, a case of mistaken identity."