Insect conservationists with the Portland-based Xerces Society don’t know yet why an estimated 25,000 bumble bees have dropped dead in a Target parking lot in Wilsonville.
They were found under a dozens of European linden trees Monday, raising the question of whether the insects were killed by a poisonous species of linden tree or by pesticide poisoning.
The bees “were literally falling out of the trees,” said Rich Hatfield, a Xerces Society conservation biologist. “To our knowledge this is one of the largest documented bumble bee deaths in the Western U.S. It was heartbreaking to watch.”
The Xerces Society has contacted the Oregon Department of Agriculture, which has collected samples of the bees and foliage from the trees. The agency will be working to determine whether pesticides were used at the site.
Hatfield said the dead bumblebees represent a loss of more than 150 colonies. He also noted dead honeybees, lady bird beetles and other insects.
“If the trees are indeed toxic, they should be cut down and replaced by something that will provide non-toxic pollen and nectar for bees,” said Scott Hoffman Black, executive director of the Xerces Society. “On the other hand, if pesticides are the cause, we need to spotlight this real-world lesson in the harm these toxic chemicals are causing to beneficial insects.”