The bright yellow and black-marked yellowjackets, generally called bees by the general public, are very abundant this fall, continuing a trend of steady increase over the past 5 to 8 years. Much of our current problem with yellowjackets is caused by the German yellowjacket (Paravespula germanica), an introduced species that migrated westward across the U.S. and arrived in Iowa in the mid 1980s. The German yellowjacket is very adept at survival in urban environments and does very well feeding on food scraps and garbage and building nests inside structure walls or in the ground in landscaped areas.
Though it is common for people to refer to the yellowjackets as bees the differences are usually easy to spot. Honey bees are golden brown or tan while yellowjackets are bright yellow with black stripes and spots. Honey bees and yellowjackets both may nest in building walls, but only yellowjackets will nest in the ground. Honey bees continue to use a nest year after year while yellowjacket nests are annual - used only one year and then abandoned. Control of both bees and wasps is the same, so distinguishing between the two may seem academic. However, honey bee nests inside house walls need to be removed to prevent problems associated with stored honey. Yellowjacket nests aremade of paper and contain no honey; they can be left inside the wall without causing further problems.
Yellowjacket nests are similar in appearance to the baldfaced hornet nests you may have seen hanging in trees. Both yellowjackets and hornets make nests of paper by stripping exposed wood fibers from trees, decks, house siding, and fences. Combs that contain individual cells for raising the offspring are built in tiers and surrounded by the outer paper covering. See drawing.
Yellowjacket Control. If a nest is located where it is out of the way and not likely to be disturbed, it is best left alone. If, however, a nest is located in a "high traffic" area such as along walks or near doorways, control is justified to reduce the threat of being stung. Nests in walls or in the ground can be destroyed by placing an insecticide dust (e.g., Sevin or rotenone garden dust) in and around the nest entrance during the night. The dust particles will adhere to the insects and control will usually be achieved within a few days. Do not plug a nest opening in a house wall until you are sure all activity within the nest has stopped.
Placing dust in a hole in the ground is usually easier than treating nests in vertical surfaces such as walls. Some imagination may be required to get the dust into the nest opening, but one possible trick is to "fling" the dust off the end of a plastic spoon. Another possibility is to "puff" the dust into the opening with an empty plastic bottle with a spout (e.g., ketchup dispenser, detergent bottle, etc.).
This article originally appeared in the August 26, 1994 issue, p. 133.