There are more pesky, stinging yellow jackets around this summer. Why it may get worse

Paige Lettington has been sighting more yellow jackets than usual in her 10-acre backyard just outside of Grass Valley. Her home has no lawn or flowerbeds — just natural vegetation — yet she still regularly sees them hovering around the property.

Lettington is not alone in these sightings. On a NextDoor thread, a swarm of residents in the Nevada City and Grass Valley area also report increased sightings of yellow jackets, or “meat bees” as some neighbors call them.

“The NextDoor thread is still going on a week and a half later with lots of people talking about how they’ve seen a lot of [yellow jackets] and what to do about them and [how] the stores are running out of traps,” Lettington said.

Climate change and worsening drought could be to blame for these increased sightings of yellow jackets, a predatory type of wasp with stingers that can sting repeatedly and even kill people who are allergic to its venom. When the natural landscape “turns to toast” as a result of drought conditions, carnivorous yellow jackets have a harder time finding their primary food source: insects.

In turn, yellow jackets become attracted to irrigated green gardens and lawns full of insects to hunt, according to Gail Langellotto, a professor of horticulture at Oregon State University, located in a state facing a similar drought crisis as California.

“Gardens become one of the new suitable habitat sites where yellow jackets can forage and find prey,” Langellotto said.

Population dynamics of yellow jackets may be shifting due to climate change. In the winter, yellow jackets typically die off by freezing or starving to death, but with winter months warming each year, more yellow jackets and their queens survive the season. As a result, “super nests” that continue into a second year are becoming more common.

While Langelloto primarily studies garden bees, she noticed patterns in yellow jacket behavior and population through her work in Portland gardens. Whenever the area experienced severe drought conditions, she noted the number of yellow jackets seen in gardens and in traps would “explode” as the surrounding vegetation dried up.

Increased sightings of yellow jackets are typical as the summer progresses. As they build up their nests from June through August, the insects’ typical peak season hits in September and lasts through October.

During her Portland garden studies, Langelloto noted increased numbers of yellow jackets later in the summer.

“It’s just the way they build up their colony over time, but when we had severe drought conditions in one particular year that we were doing our study, then it was noticeable how many more yellow jackets were in the yard,” she said.

This year, Langelloto has not seen many yellow jackets as the peak season has not hit yet. Since Oregon has been under consistent drought conditions, much like California, it’s possible that more sightings will come later in the summer.

“In August is when we would really start seeing the large numbers of yellow jackets, sometimes in late July,” Langelloto said.

Wasps and yellow jackets searching for water sources

In the Sacramento area, the Sacramento-Yolo Mosquito and Vector Control District has received some yellow jacket-related requests this month, but the number of reports has been nothing out of the ordinary, according to Luz Maria Robles, the public information officer for the Sacramento-Yolo Mosquito and Vector Control District. The numbers of yellow jackets sighted in traps have been normal as well.

Jamie Davenport, one of the managers at Official Pest Prevention in Elk Grove, has recently seen an increase in all kinds of pests in the area — not just yellow jackets — which he believes is a result of the drought.

“A lot of these pests start coming towards the home because they’re looking for shelter and water,” Davenport said.

To prevent yellow jackets and other pests from entering homes, Davenport recommends sealing off cracks and holes in windows, doors and home walls. As the drought situation worsens, he thinks yellow jacket sightings in backyards will increase as the insects search for water sources.

“If we continue to be in a drought-type situation where the water is scarce, it’s going to force [yellow jackets] to look for water and shelter, and around somebody’s home is usually a prime spot for them to find all of those things,” Davenport said.

As a former resident of Sacramento for 30 years, Lettington does not remember having an issue with yellow jackets before moving near Grass Valley. Instead, she remembers dealing with paper wasps, which build honeycomb-like nests in the eaves and gutters of homes.

Last Friday, the National Weather Service issued an excessive heat warning for multiple cities in northern California including Grass Valley, because of “widespread, dangerously hot conditions.” With temperatures in Grass Valley soaring as high as 106 degrees this past weekend, the warning remained in effect through Monday evening.

Unaware of the location of the yellow jacket nest in her backyard, Lettington uses traps to keep the number of yellow jackets at bay. Per some suggestions on the NextDoor thread and from the directions on the traps, Lettington plans to put her traps out earlier next year, to catch the queens before they nest and reproduce.

How to avoid wasp and yellow jackets

To prevent yellow jacket encounters, Langelloto agrees that placing traps early in the season can help suppress colony numbers and avert infestations in later months. She also warns that because yellow jackets are carnivorous, eating meat outdoors could attract yellow jackets.

“Just know that having an outdoor picnic with meat may put you in direct competition with yellow jackets for food and you may want to plan to have your picnic elsewhere,” Langellotto said.

Removing rotting fruit, soda and other foods can prevent attracting yellow jackets in backyards as well, said Heather Stoven, an extension horticulturist with Oregon State University.

Just because yellow jackets show up in gardens one year also does not mean that they will come back. Yellow jackets abandon their nests each season, so Langellotto recommends waiting for them to leave, instead of spraying insecticides that kill other beneficial insects in gardens, beyond targeted yellow jackets.

Because of the many benefits that yellow jackets bring to gardens, such as keeping pest insects in check, Langellotto recommends leaving nests alone, if possible.

“The benefits that yellow jackets bring to a garden and garden ecology are oftentimes dismissed or overlooked because people identify yellow jackets or the nuisance factor first and foremost,” Langellotto said.

Lettington does not find the yellow jackets in her yard to be a nuisance. These yellow jackets have never stung Lettington or her family, so she said they are really only a problem when her family is eating outside.

As the drought ensues, it is possible that more yellow jackets will show up in gardens. Planting drought-tolerant, native plants and reducing irrigation in gardens can help prevent possible infestations, according to Langellotto.

“This has the potential to be a year where we see quite a few of them,” Stoven said.

This story was originally published July 13, 2021 at 5:00 AM with the headline "There are more pesky, stinging yellow jackets around this summer. Why it may get worse."