Oregon officials say a pesticide is to blame for the deaths of an estimated 25,000 bumble bees in a shopping center parking lot.
The state Department of Agriculture said Friday that tests on bees and foliage showed the deaths are "directly related to a pesticide application on linden trees" that was meant to control aphids.
It said an investigation is underway to see if the application of the pesticide Safari, done last Saturday, violated the law.
To prevent more deaths, bee-proof netting is planned for 55 European linden trees whose blooms attracted the pollinators to the Target parking lot in Wilsonville, southwest of Portland.
State officials are working with the Xerces Society for Invertebrate Conservation, the city of Wilsonville and the distributor of the pesticide.