25,000 Bumblebees Die After Trees Sprayed With Pesticides

Over 25,000 bumblebees died in a mass mystery bee kill in the parking lot of a Target store in Wilsonville, Oregon. Now conservation workers are trying to track down the cause of the massive bee die-off which insect advocacy group The Xerces Society For Invertabrate Conservation said could be one of the largest ever bumblebee mass deaths documented in the United States.

Xerces received the first reports of the mystery bumblebee die-off on Monday. According to a press statement, they received multiple phone calls complaining about the dead bees. Xerces Rich Hatfield went to the site to check it out.

“They were literally falling out of the trees,” Hatfield said. He reported that he saw at least 25,000 dead bumblebees, which could represent 150 lost colonies.

There were also dead honeybees and other species of insect pollinators.

Coming on Monday, the grim discovery was an upsetting beginning to National Pollinators Week — an event planned to raise awareness of the ongoing disappearance of bees.

At that time, Xerces didn’t know if the cause was pesticide spraying or a poisonous variety of linden trees. They asked the Oregon Department of Agriculture (ODA) to test the bees and foliage to figure out what was going on.

The Oregonian reported on Wednesday that the bumblebees were still dying. Reporter Elizabeth Case described a grim scene:

“Yellow-faced bees fell from the trees, twitching on their backs or wandering in tight circles on the asphalt. Some honeybees and ladybugs were also found dead. A few dead bumblebees even clung to linden flowers, while hundreds littered the lot.”

ODA’s director of plant programs Dan Hilburn said the trees were sprayed Saturday with an insecticide called Safari. However, ODA is still testing other pesticides that have also been recently used in the area. A final report on the cause of the bumblebee death may take a few more days.

The directions for using Safari clearly state that it can’t be used if bumblebees or other bees are present. If the pesticide was sprayed improperly, the state of Oregon may seek sanctions.

The bumblebee may be Oregon’s most important pollinator, so it’s vital to the agricultural economy.  Here’s a British video about the economic and ecological importance of bumblebees:

The landscapers and land owners didn’t respond to Case’s request for comments on the bumblebee die-off.

[bumblebee photo by Ian Grainger via Shutterstock]