Questions remain about why thousands of bumblebees died off

Questions remain about why thousands of bumblebees died off »Play Video
A member of the Oregon Department of Agriculture collects samples from a tree where hundreds of bumblebees dropped dead. Investigators suspect an insecticide killed the bees. Crews placed netting over the tree to keep bees from being poisoned.

PORTLAND, Ore. – State investigators think the same chemical likely killed hundreds of bumblebees in Hillsboro and thousands in Wilsonville.

That chemical is Safari, an insecticide.

The chemical has been used for a long time but investigators haven't seen any similar die-offs around here. There are questions about timing and why in Hillsboro it's only one tree that's poisonous.

A worker with the Oregon Department of Agriculture climbed into that tree in Hillsboro on Monday and collected samples to see how toxic it is. Crews placed netting over the tree to keep bees from being poisoned.

On the ground there were hundreds of bumblebees already dead or dying. The die-off was first noticed Friday.

But the tree and 200 others in downtown Hillsboro were sprayed in March by city crews with Safari to kill aphids.

"I know this is the third year the city of Hillsboro has done this type of spraying, and this is the first time we've seen anything like this with hundreds of bees on the ground," said city spokesman Patrick Preston.

Bees also died by the thousands at the Target store in Wilsonville after trees there were recently sprayed with Safari by a private contractor. 

According to the Department of Agriculture, it will look at how much was sprayed and when.

Dan Hilburn, with the department, said by phone he's never seen a die-off like this.

"I'm not an expert in pollination, pollinators, but I've been around entomology my entire career, and I've never seen or heard anything like this with bumble bees," he said.

The city of Portland doesn't use pesticides like Safari on trees in its parks. Instead, it lets natural predators take care of pests.

"(Safari) is a very soluble insecticide," said John Reed with Portland parks. "It is my understanding Safari goes into the tree quite quickly, moves up through the vascular system and out into the leaves and out into whatever is feeding on it."

The Hillsboro tree is not very healthy and an arborist is wondering if that's a factor in why it became toxic.

In Wilsonville, the city covered 55 trees at the Target store to protect bees from being poisoned.

The state's not worried about the bee population in this case.

Each pesticide comes with specific instructions on when and how they're used.