Yellowjacket Wasp

Description of yellowjacket wasps

Late summer is the time of year when populations of yellowjackets (commonly called "bees") and other social wasps become large and noticeable. The wasps have been present since spring, but because colonies start as a single queen in May, populations are very small through the early part of the summer. Yellowjacket wasp populations reach a peak at about the time of the Iowa State Fair when each nest may have up to approximately 5,000 wasps.

Yellowjackets build paper nests similar to hornets, but either in the ground, a log or landscape timber or building wall or attic. Yellowjackets are commonly observed hovering back and forth at the small nest opening or around garbage cans and other areas where they forage for food. The workers from the colony travel up to a few hundred yards from the nest while looking for food. In the early summer the wasps forage for caterpillars and other "meat" items, but in the fall prefer sweets such as pop and candy residue in garbage cans.  

Management of yellowjacket wasps

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.

Pest management professionals can be utilized and only attmpt to control a colony yourself if you know you are not allergic to wasp stings.  Nests in walls or in the ground can be destroyed by placing an insecticide dust containing carbaryl in and around the nest entrance during the night. The dust particles will adhere to the insects as they leave and reenter the nest 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. For more information on insecticides please read this article.

In The Home

Yellowjacket wasps build annual colonies in the ground, or in holes in building walls and foundations. Nests built into wall voids or attics are often the source of wasps that invade the living space within the house, especially in the fall and early winter.

In fact, yellowjackets in the house after the time of frost and the first freezing weather are almost certainly originating from a nest in a wall of the house. The nest has been in the wall since spring and the wasps spent all summer using a "front door" from the nest that lead outdoors into the yard where they fed on caterpillars and nectar. When the food sources disappeared after frost, and when it got cold out in the yard, the wasps turned to exploring the warm side of the wall and found a "back door" into the living space of the house. Wasps inside the house are often sluggish, but may be active enough to sting if the temperature is sufficiently warm.

Yellowjacket nests are annual, and the workers that comprise the majority of wasps within the nest all die with freezing weather. The annoyance of wasps emerging into the house is temporary, but heat from the furnace, warming the walls, keeps a very few of them alive longer than usual.

The practical control is to swat wasps as they emerge from the walls, and wait for the remainder to die of old age and cold weather. Spraying is of little to no benefit. Plugging gaps where the wasps are coming through the wall would help but we almost never know where the nest is located or where the wasps are getting in. The problem will go away in time, certainly by the time winter "really" gets here. Yellowjacket wasps do not reuse a nest the following year and the wasps emerging inside the house will not establish new colonies nor reproduce during the winter.

Do you live in Iowa and have an insect you would like identified?

The Iowa State University Plant & Insect Diagnostic Clinic will identify your insect, provide information on what it eats, life cycle, and if it is a pest the best ways to manage them.  Please see our website for current forms, fees, and instructions on preserving and mailing insects.   

Contact information for each states diagnostic laboratory for U.S. residents.  If you live outside of Iowa please do not submit a sample without contacting the Plant & Insect Diagnostic Clinic.