CORVALLIS, Ore. – Yellow jackets buzzing around pop cans, hamburgers and fruit salad can ruin barbecues. And, because their sting can be life-threatening, it might be necessary to destroy nests found near human activity.
It's easier to deal with these aggressive wasps if you know how they live, said Ross Penhallegon, horticulturist with the Oregon State University Extension Service. Yellow jackets are heavy-bodied, with black and yellow or white markings and live in gray, papery nests, which are mainly located below ground but some are suspended above, he said.
"Not to be mistaken as honeybees that gather pollen and flower nectar, yellow jackets are mostly meat eaters and are particularly fond of rotting fruit," Penhallegon said. "Yellow jackets are more likely than bees to sting without provocation, their sting is more painful and normally no stinger remains in the skin. A single yellow jacket may sting more than once."
"Worker" yellow jackets hunt for insects or feed on carrion or rotting fruit. They carry food back to the nest to feed their nest-mates. If you accidentally contact a nest entrance, you're likely to get stung. Workers vigorously defend the nest and queen.
A queen is the epicenter of each nest and her sole responsibility is to lay eggs. She begins a nest in the spring by laying a few eggs and raising the adults. Workers provision, expand and defend the nest.
As spring and summer pass, the nest grows and new workers assume their role. By the end of summer, nests may contain hundreds or thousands of workers. By August or September, they are at their most troublesome and dangerous.
By fall, yellow jacket nests have produced a crop of new queens and males. By the first frost, most workers and queens leave the nest to find a protected spot to spend the winter. They re-emerge in spring to begin the cycle again. Only new queens survive the winter, however, and they almost never reuse the previous year's nest.
To destroy a yellow jacket nest, treat the nest at night, when the workers are inside and relatively calm. Use an aerosol that propels a stream of insecticide up to 20 feet so that you can stand at a safe distance and treat directly into the nest opening.
"Don't pour petroleum products into ground nests," Penhallegon said. "This is dangerous, environmentally harmful and illegal. Use products specifically made for yellow jacket control only. Be sure to read and follow the pesticide product label. Remember, the label is the law."
Non-toxic yellow jacket traps are available in yard and garden stores. The most effective traps use a synthetic attractant to lure worker yellow jackets into a trap. Fruit juice or meat can be used as attractants as well. Traps may provide temporary relief by drawing workers away from people, but they are not effective for area-wide nest control.
Some people are allergic to the venom of yellow jackets and stings can be deadly. Persons particularly sensitive to yellow jacket venom should be extra cautious in late summer and early fall, when the insects are most numerous. Enlist the help of someone not as sensitive, if you need to spray a nest.
Other wasps are mud daubers and paper wasps. Mud daubers collect bits of wet soil to take back to their nests, usually a mud tube. Paper wasps build small, open nests that are suspended vertically from a horizontal surface, such as under an eave, bush or tree branch. Their long legs and thin "waists" distinguish paper wasps. Both mud daubers and paper wasps are less aggressive and normally will not sting or swarm when away from their nest.