Column
Yellowjackets, pros, cons, and control
By John Fulton

[September 25, 2014]  With the fall festival season comes the onslaught of yellowjackets, and the calls have been rolling in to the office. Yellowjackets are beneficial insects in the sense that they pollinate plants and feed other insects and carrion (dead meat) to their larvae. Many times they will prey on insects that we identify as pests.

Unfortunately, their ability to sting makes them a considerable health concern. Yellowjackets alone are responsible for about one-half of all human insect stings. The stings of social wasps, such as yellowjackets, have evolved as a defense mechanism. The only purpose for the sting is to inflict pain. Yellowjackets are easily provoked and, unlike honeybees, can sting more than once. They will attack in force if their nest is disturbed. Unless a person is allergic to yellowjacket venom, stings are rarely life threatening.

Yellowjackets are most frequently encountered when they scavenge for food. Their habit of feeding on nectar and sugar can create a nuisance. Yellowjackets are attracted to open cups and cans of soda and other sweet liquids. This year it seems like hummingbird feeders are also a favorite. They are also attracted to open cans of garbage, bright flowery clothing, and floral scented perfumes. All outside garbage cans must be kept clean and well covered, to reduce yellowjacket problems. Contact with the wasps can be decreased by reducing these attractions at picnics and other outings. In situations closer to home, the elimination of overripe fruit from gardens and orchards will dramatically decrease the number of scavenging yellowjackets. Holding gatherings indoors and using screens on windows will also help avoid yellowjacket problems.

There are a variety of traps on the market that claim to attract yellowjackets. These traps are baited with the scent of rotting fruit or other odors equally as appetizing to the yellowjackets. It is questionable whether these traps can out-compete the natural and man-made attractants described above. However, it is certain that through proper sanitation and removal of natural and man-made attractants, yellowjacket contact can be reduced. However, in situations where the potential for repeated contact exists, other management methods may be necessary. These traps can also attract more yellowjackets if placed close to the home or patio, so place them to attract the insects away from where you’ll be.

Management of each species of yellowjacket differs because of their nesting habits. Both species do not reuse their nests, therefore what was a problem this year may not occur next year. Caulking cracks and crevices in structures in winter and early spring, after the nests have died, will prevent German yellowjackets from constructing nests inside buildings. Openings to active nests should not be caulked. Chemical control for ground-nesting yellowjackets consists of drenching the exit hole with an approved insecticide, such as Sevin, and plugging the hole with treated soil or cotton balls. Yellowjackets that are not killed by the initial treatment will be killed by chewing on the treated cotton ball or tunneling through the soil.

 Yellowjacket entrance holes in buildings can be treated with approved insecticide dusts. As the yellowjackets walk through the dust they pick it up on their legs and transport it into the nest. When yellowjackets groom themselves they ingest the dust on their legs. It may take up to a week for the colony to die and repeated chemical applications may be necessary. When the entrance hole of an active nest is in a building, the hole should not be plugged with the insecticide or caulked. The yellowjackets may decide to chew through the soft inside wall rather than chew through the insecticide or caulking material.

Implement chemical control measures at dusk or dawn when the wasps are in their nest. Wear protective clothing when attempting to eliminate the nests, such as long sleeved jackets, gloves, and pants. Tape the wrists and ankles to the clothing, to prevent the wasps from getting underneath the clothes. A bee veil or other enclosed form of face and neck protection should also be worn. Yellowjackets will defend their nest, so to avoid being attacked, use a flashlight covered with red cellophane when applying the insecticide at night, since yellowjackets are unable to see red.

[By JOHN FULTON, COUNTY EXTENSION DIRECTOR SERVING LOGAN, MENARD, AND SANGAMON COUNTIES]