CA drought, climate change cause increase in yellow vests


Paige Lettington spotted more yellow jackets than usual in her 10 acre garden just outside of Grass Valley. Her home doesn’t have a lawn or flower beds – just natural vegetation – but she still sees them regularly floating around the property.

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

“The NextDoor thread is still running a week and a half later and a lot of people are talking about how they’ve seen a lot [yellow jackets] and what you can do about it and [how] stores are running out of traps, ”Lettington said.

Climate change and worsening drought could be responsible for these increased sightings of yellow vests, a predatory species of wasp with spines that can repeatedly sting and even kill people allergic to its venom. When drought turns the natural landscape into toast, carnivorous yellow vests have a harder time finding their primary food source: insects.

In turn, yellow vests are drawn to irrigated green gardens and lawns full of insects, according to Gail Langellotto, a horticultural professor at Oregon State University, in a state with a similar drought crisis to California.

“Gardens are becoming one of the new habitats in which yellow vests can forage for food and find prey,” said Langellotto.

The population dynamics of the yellow vests can shift due to climate change. In winter, yellow vests usually die from freezing or starvation, but as the winter months warm up each year, more yellow vests and their queens survive the season. As a result, “super nests” that last into a second year are becoming more common.

While Langelloto primarily studies garden bees, through her work at Portland Gardens she noticed patterns in the behavior and population of yellow vests. Whenever the area suffered severe drought conditions, she found that the number of yellow vests seen in gardens and traps “exploded” as the surrounding vegetation dried up.

During the summer, increased sightings of yellow vests are typical. While they build their nests from June to August, the typical high season for insects begins in September and lasts until October.

Later that summer, while studying gardening in Portland, Langelloto noticed an increased number of yellow vests.

“It’s just how they build their colony over time, but when we had severe drought conditions in a given year that we did our study, it was noticed how many more yellow vests were in the garden,” she said.

Langelloto has not seen many yellow jackets this year as the main season has not yet entered. Since Oregon, much like California, suffered from constant drought conditions, it is possible that more sightings will come later this summer.

“We would really see the large numbers of yellow vests in August, sometimes at the end of July,” said Langelloto.

Wasps and yellow vests in search of water sources

In the Sacramento area, the Sacramento-Yolo Mosquito and Vector Control District received some inquiries related to the yellow jacket this month, but the number of reports has been according to Luz Maria Robles, the Sacramento-Yolo Mosquito and Vector Control District public information officer . The number of yellow vests sighted in traps was also normal.

Jamie Davenport, one of the managers of Official Pest Prevention at Elk Grove, has recently seen an increase in all types of pests in the area – not just yellow vests – which he believes were due to the drought.

“A lot of these pests come towards the house looking for shelter and water,” Davenport said.

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

“If we continue to find ourselves in a drought-like situation where water is scarce, it will force [yellow jackets] looking for water and shelter, and someone’s neighborhood is usually a prime place to find all of those things, ”Davenport said.

A retired Sacramento resident for 30 years, Lettington cannot recall having a problem with yellow jackets before moving to the Grass Valley area. Instead, she remembers paper wasps that build honeycomb-like nests in gutters and gutters.

Last Friday, the National Weather Service issued an excessive heat warning for several cities in Northern California, including Grass Valley, because of “widespread, dangerously hot conditions.” With temperatures in Grass Valley rising as high as 106 degrees last weekend, the warning stayed in effect until Monday evening.

Unaware of the location of the yellow vests nest in their back yard, Lettington uses traps to keep the number of yellow vests at bay. After some suggestion on the NextDoor thread and instructions on the traps, Lettington plans to expose their traps early next year to catch the queens before they nest and reproduce.

How to avoid wasps and yellow jackets

To prevent encounters with yellow vests, Langelloto agrees that setting traps early in the season can help suppress colonies and stave off infestation in later months. She also warns that eating meat outdoors could attract yellow vests since yellow vests are carnivores.

“Just know that if you have an outdoor picnic with meat, you can be 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 also prevent yellow vests from being donned in backyards, said Heather Stoven, a grower at Oregon State University.

Just because yellow jackets show up in gardens a year from now doesn’t mean they will come back. Yellow vests leave their nests every season, so Langellotto recommends waiting for them to go instead of spraying insecticides that kill other beneficial insects in gardens than targeted yellow vests.

Due to the many advantages that yellow vests have for gardens, such as repelling pests, Langellotto recommends leaving nests alone if possible.

“The garden and garden ecology benefits that yellow jackets bring are often dismissed or overlooked because people primarily identify yellow jackets or the annoying factor,” said Langellotto.

Lettington doesn’t find the yellow jackets disturbing in her garden. Those yellow jackets have never stung Lettington or her family so she said their really only problem is when her family is eating outside.

If the drought breaks out, it is possible that more yellow vests will show up in gardens. Planting drought-tolerant, native plants and reducing watering in gardens can help prevent possible infestation, according to Langellotto.

“This has the potential to be a year we see some of these,” said Stoven.

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Margo Rosenbaum is an intern for summer reporting at The Sacramento Bee. She is attending UC Davis where she is studying two majors in communication and evolution, ecology and biodiversity. Margo also works as Editor-in-Chief for The California Aggie.

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