Just as Pollinator Week began last week, an estimated 50,000 bumblebees, likely representing over 300 colonies, were found dead or dying in a shopping mall parking lot in Wilsonville, Oregon. Authorities confirmed Friday that the massive bee die-off was caused by the use of a neonicotinoid pesticide, dinotefuran, on nearby trees. Then on Saturday, it was reported by The Oregonian that what could be hundreds of bees were found dead after a similar pesticide use in the neighboring town of Hillsboro.

According to the Xerces Society, this is the largest known incident of bumblebee deaths ever recorded in the country. Bumblebees, which are crucial to pollination of multiple berry and seed crops grown in the Willamette valley, have recently experienced dramatic population declines, a fate that is similar to other pollinators. Dan Hilburn, Director of plant programs at the Oregon Department of Agriculture (ODA), told Oregon Live that he’s “never encountered anything quite like it in 30 years in the business.” The incident highlights the difficulty of permitting in commerce such a highly toxic material that indiscriminately kills beneficial insects.

A recent study, An overview of the environmental risks posed by neonicotinoid insecticides, published in the Journal of Applied Ecology, documents that neonicotinoid persistence in soil and water can cause broad and far-reaching impacts on ecosystem health, much of which have undergone little scientific scrutiny. The author asserts that world leaders have failed to meet their commitment made at the 2002 Convention on Biological Diversity – to achieve a significant reduction in the rate biodiversity loss. He points to neonicotinoids as a potential cause of this failure, due to their long-term persistence in soil and water. He specifically points to soil dwelling insects, benthic aquatic insects, grain-eating vertebrates, and pollinators as being in particular danger from the use of these chemicals.

The ODA and Xerces Society had been working together to investigate the pesticide poisoning. After interviewing the landscaping company that maintains dozens of ornamental trees around the parking lot, ODA investigators learned that Safari, a pesticide product with the active ingredient dinotefuran, had recently been applied on Saturday, June 15 to control aphids. Dinotefuran is a neonicotinoid pesticide that is highly toxic to bees; the product’s label strictly forbids its use if bees are in the area.
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