Bees and Banned Pesticide: Die-Off in Portland, Ore.

More than 400 bees--most of them bumblebees--were found dead in Portland, Ore. in mid-to-late June. The four bee die-offs that occurred in the Portland area that month were among several major bee die-offs to occur in the past two years, as The Oregonian reported.

A state probe by the Oregon Department of Agriculture (ODA) recently released results that lethal levels of the pesticide imidacloprid, which the ODA banned in February, as reported by The Oregonian. Imidacloprid is a type of neonicotinoid--a class of systemic insecticides implemented in colony collapse disorder.

All of the bees were found near linden trees--a type of tree often sprayed with chemicals to control aphids, as The Oregonian article noted. 

Investigators with the ODA have determined, by interviewing owners and managers of the property on which the bees died, that chemical applications to the trees took place before the ban went into effect, The Oregonian reported.

The coordinator of a pesticide study program with Eugene, Ore.-based Xerxes Society for Invertebrate Conservation, Aimee Code, said the ODA's news was a cautionary tale for other states and the federal government, which have not yet limited the use of neonicotinoid pesticides.

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