Sept. 16, 2014
LINCOLN, Neb. — Late summer is the season for yellow jacket wasps, but there are steps that can be taken to control them.
"Yellow jackets are some of the more common stinging insects homeowners may encounter," said Jonathan Larson, University of Nebraska-Lincoln Extension educator in Douglas/Sarpy counties.
Based on reports to some extension educators, yellow jackets seem to be more common this year. Larson said he's had about 50 people contact him the last two weeks. "I would guess that the kind of wet summer with high but not hot temperatures helped them survive better this year in comparison to the drought-stricken summers of the last two years," he said.
These social wasps build their nests underground in abandoned rodent burrows, under compost piles, in voids of wood and sometimes in trees or shrubs. The nest is constructed out of paper and holds the queen and her many workers, Larson said. Yellow jacket colonies can number between 500 and 5,000 individual insects. The nest is annual, meaning that only new queens survive for the winter, the rest die out at the first hard freeze of the year.
A yellow jacket worker is about ½ inch long with alternating yellow and black bands on the abdomen. They will look different than honey or bumble bees as these beneficial pollinating insects have hairy bodies, while the yellow jacket is smooth and glossy in appearance. They are an important health pest due to their aggressive nature when disturbed and the fact that individual wasps can sting multiple times.
These wasps are carnivorous and feed on a variety of insects and spiders, but also enjoy finding sweet treats such as soda pop or fruit at a picnic. While they are not important pollinators, they do help control pests such as caterpillars.
Encounters with humans often occur during mowing or when working with outdoor trash cans. An upswing in foraging activity occurs as summer ends, which results in an increase in cases of people being stung. If a colony has been disturbed, cover your face with your hands and slowly retreat from the area towards a building, car, or dense vegetation. Do not run as the swift motion may attract more yellow jackets.
Control of a yellow jacket colony should be done at dusk or after dark when the insects are the least active. If you choose to wait until dark, a flashlight covered with red cellophane can help you see (insects do not perceive red light). Care should also be taken to wear long sleeves, a hat, and pants to try and ensure protection from possible stings.
Chemical control options include aerosol products with a jet trigger like cypermethrin (Raid® Wasp and Hornet Killer) or lambda cyhalothrin (Spectracide® Wasp and Hornet Killer). Insecticide dusts like carbaryl (Sevin®) or permethrin (Eight®) will also provide strong control. Successful control is dependent upon getting the insecticides inside the colony. Spraying wasps that are flying in your vicinity or that are visible outside of the nest will not lead to total elimination. Therefore, locate the entrance to the nest and then spray or sprinkle the insecticide into the entrance at dusk and leave the area. Wait at least 24 hours and return to see if the job has been finished. If not, repeat the previous steps. After successful elimination, seal the entrance with soil, wood, or caulk (depending on nest location) so that reestablishment doesn't occur.
Both aerosols and dusts will work for ground or cavity nests but the jet propelled aerosols are best for aerial nests. Non-chemical control of yellow jackets includes using solid waste receptacles (i.e. no wire mesh) that have wasp-tight lids to prevent workers from entering the can.Jonathan Larson
UNL Extension Educator
IANR News Service