Introduction

Hornets, yellowjackets, and paper wasps differ from bees in that their bodies are slender with a narrow waist and they are mostly hairless and shiny. These social insects live in colonies consisting of a single reproductive queen and infertile female offspring (workers). All three stinging insects build gray, papery nests from fibers they chew from weathered wood.

Most wasps and hornets prey on other insects and are considered beneficial. However, once they congregate around human gathering places, they can become a nuisance. All of these insects are able to inflict multiple, painful stings with a barbless stinger.

Yellowjackets

Four of the eleven yellowjacket species in Idaho pose stinging hazards that justify control measures. These species are the western yellowjacket, common yellowjacket, German yellowjacket, and aerial yellowjacket (Figure 1). They readily nest around homes and build their nests underground in abandoned animal burrows or other hollowed-out spaces. Yellowjackets are attracted to honeydew produced by aphid colonies in trees.

Bald-Faced Hornets

These are large, stout-bodied black wasps with a whitish-yellow face and some white marks near the end of the body (Figure 2). They build their nests aboveground on plants or buildings. The nests often have leaves or twigs in the outer wall. Hornets are not particularly aggressive and pose a much lower stinging hazard than yellowjackets. They feed almost entirely on insects (including yellowjackets) and are not generally considered a nuisance at outdoor events.

Paper Wasps

The most common wasp in Idaho is a non-native species called the European paper wasp. This insect has a longer, slimmer body than a yellowjacket. It has a long-legged appearance and dangles its legs while in flight (Figure 3). It builds a distinctive, umbrella-shaped, open nest that hangs upside down from protected locations. It is fairly docile and normally only stings when trapped.

Management Strategies

Nonchemical Control

Recognize that applying repellents or flooding subterranean nests are ineffective control measures. In most situations, insecticides are required for control. Other practical strategies to help reduce stinging risk include the following:

Make yourself and your surroundings less attractive to the insects.

• Do not wear perfume when working outside
• Wear light-colored clothing
• Keep food covered during picnics
• Keep lids on trash cans
• Remove rotting fruit from under trees
• Control populations of aphids

Destroy early season nests in problem areas during April and May. Nests can be dislodged with a garden hose. Never knock down, cut, and bag large nests because the stinging hazard is too high.

Know how to behave in an encounter. If you encounter one or more of these stinging insects, walk backward and move slowly away from the insect. If you hear loud buzzing, seek shelter in a building or vehicle until the wasps stop their pursuit.

Use traps. Yellowjackets are fairly easy to trap with commercial or homemade traps. However, these traps don’t attract paper wasps. Avoid placing traps close to areas where humans congregate.

Chemical Control

The most effective chemical control products are liquids or aerosols specifically designed to shoot a narrow stream of insecticide that is applied from a distance. Most wasp- or hornet-control products contain pyrethroids; look for products with the active ingredients cyfluthrin, beta-cyfluthrin, bifenthrin, lambda-cyhalothrin, deltamethrin, permethrin, or tralomethrin. Be sure to follow label instructions during application. For a more detailed list of insecticides and control methods, refer to Homeowner Guide to Yellowjackets, Bald-Faced Hornets, and Paper Wasps online at http://www.cals.uidaho.edu/edComm/pdf/BUL/BUL0852.pdf.