JoAnne Skelly: Yellow jacket wasps out in force

I may be imagining it, but it seems like a particularly bad yellow jacket year, even though they seemed to arrive later. One area of our yard hums with thousands of them. These aggressive nest defenders aren’t frightened by humans. In fact, swatting one away merely pisses it off. Anyone ever stung by a yellow jacket knows a sting hurts, burns, itches and seems to last a long time. Even worse, one wasp can sting repeatedly. It’s quite an unwelcome and painful surprise to drink from a soda can with a yellow jacket in it. Just a few ruin a good picnic or barbecue in a hurry. For people who are allergic, a sting can be life-threatening.

The term “yellow jacket” refers to a number of different species of wasps.

They commonly build paper nests in rodent burrows, but sometimes nest in other protected cavities, such as voids in walls and ceilings of houses. Some build nests in trees, which is the case at our house. If a rodent hole isn’t spacious enough, yellow jackets will increase the size by moistening the soil and digging it out. Similar behavior inside a house sometimes leads to a wet patch that develops into a hole in a wall or ceiling. Colonies, which are begun each spring by a single reproductive female, can reach populations of between 1,500 and 15,000 individuals, depending on the species (UC Davis IPM).

Although yellow jackets are predators of other insects, their aggressive behavior makes them unwelcome companions near people or pets. Ideally, avoid their nesting places. Sometimes this is easier said than done. My husband was stung repeatedly after disturbing a ground nest while mowing weeds. “Keep foods, including pet food and drinks, covered or inside the house, and keep garbage in tightly sealed garbage cans. Once wasps discover food, they will continue to hunt around that location long after the source has been removed,” (UC Davis IPM).

Traps that attract yellow jackets into an inescapable container using a chemical lure are available wherever pest control products are sold. They usually work on small populations. Even though insecticides are sold to control wasps, the wasps get very upset when their nest is sprayed, and will often attack the applicator. When spraying wasp nests, spray when it’s cool and be sure to wear protective clothing that covers you completely, including a veil over your face and thick gloves. Or, call a professional.

For more information, visit the University of California, Davis, Integrated Pest Management site at

JoAnne Skelly is Associate Professor & Extension Educator, Emerita at University of Nevada Cooperative Extension. She can be reached at


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