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Know thy enemy—a primer on yellow jackets
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October 8, 2010
CORVALLIS, Ore. – Summer is the time when yellow jackets become a problem, especially when it is hot and dry. It helps to become familiar with the natural history of these stinging insects to be better able to cope with them.
Yellow jackets are heavy-bodied wasps, with black and yellow or white markings, explained Ross Penhallegon, horticulturist with the Oregon State University Extension Service. They live in gray, papery nests, located either below ground or suspended above the ground.
"Worker" yellow jackets hunt for insects, or feed on carrion or rotting fruit. Workers are attracted to any meat-based or sugary item. Food is carried back to the nest where it is fed to nest-mates. Stings usually occur through accidental contact with the nest entrance. Workers vigorously defend the nest and queen against intruders.
A queen is the epicenter of each yellow jacket nest. Her sole responsibility is to lay eggs. She begins a nest in the spring by laying a few eggs and raising these workers to adults. At this point, the queen may no longer leave the nest to hunt. Workers provision, expand and defend the nest. As spring and summer pass, the nest grows as new workers are reared and assume their role. By the end of summer, nests may contain hundreds or even thousands of workers. So by August or September, these venomous social insects are the most troublesome and dangerous.
By fall, yellow jacket nests have also 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 reemerge in spring to begin the cycle all over again.
There are three points to remember, Penhallegon says. Only new queens survive the winter, these queens almost never reuse the previous year's nest the following spring, and in certain regions, there are professionals who may collect yellow jackets to collect the venom for pharmaceutical use. Your local county office of the OSU Extension Service may be able to refer you to these collectors.
CONTROL OF THE NUISANCE NEST: It might occasionally be necessary to destroy a yellow jacket nest because it is near human activity. Here are some suggestions for safe and effective nest removal.
Treating the nest at night helps because the workers are inside and relatively calm.
Use one of the aerosols that propel a stream of insecticide "up to 20 feet" so that you can stand off at a safe distance and treat directly into the nest opening.
Don't pour petroleum products into ground nests. 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. The label is the final word on what does or does not constitute a legal and safe application.
POISON BAITS: Finding below-ground nests is difficult, so pest control professionals may resort to use of poisoned baits to achieve area-wide control. Poisoned baits can be extremely hazardous, but are effective for severe yellow jacket infestations. Baits work by luring the worker yellow jackets to carry a bit of poisoned food back to the nest, thereby getting the poison to those in the nest. These baits contain an encapsulated insecticide. The instructions accompanying the insecticide describe how to use it and must be followed exactly. Bait stations must be protected, so that other animals cannot get to the poisoned bait. Poisoned baits should only be used after about July 15, when nests have begun to expand rapidly. Prior to this date you risk disrupting beneficial species.
TRAPPING: 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 various meats can be used as attractants as well. Traps may provide some temporary relief by drawing workers away from people, but they are not effective for area-wide nest control.
A NOTE ON REACTIONS TO STINGS: Some people are allergic to the venom of yellow jackets and others are allergic to bee stings. Both reactions can be life-threatening to some people. If you are particularly sensitive to yellow jacket venom, 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. Bee stings can occur anytime bees are out of their hives, but are far less common than yellow jacket stings. Never attempt to remove or destroy honeybee hives.
If a bee stings you remove the stinger immediately; don't squeeze it, just scrape it away with your fingernail. Both honeybees and yellow jackets inject venom with their stingers. The venoms are different in each, so a person may react differently to each. It is possible to be severely allergic to one and not even sensitive to the other.
To tell the difference between a yellow jacket and a honeybee, it helps to watch their behavior. Honeybees gather pollen and flower nectar, while yellow jackets are mostly meat eaters, but will take plant and fruit juices also. Yellow jackets are particularly fond of rotting fruit. Yellow jackets are more likely than bees to sting without provocation, their sting is more painful, and normally no stinger remains in the skin and a single yellow jacket may sting more than once. Honeybees are much less likely to sting and their sting is not so painful. A honeybee leaves behind its stinger and a single bee can sting only once.
Other wasps you may have noticed are the mud daubers and paper wasps. You'll see mud daubers around wet soil collecting bits 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. 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.
To learn more about honeybees and yellow jackets and other insects, visit the following OSU websites:
Source: Ross Penhallegon