The conservation group Xerces Society is pushing to ban the pesticide used in trees where two large bee die-offs occurred in two Oregon towns in less than a week.

On Friday, the city of Hillsboro started getting calls about hundreds of dying bumblebees falling from a tree downtown.

By Saturday, crews had covered the tree in protective netting.

“At this point we’re waiting for the Oregon Department of Agriculture to tell us what’s going on,” said Patrick Preston, Public Affairs Manager for the City of Hillsboro.

The problems in Hillsboro started just days after a massive bee die-off at a Wilsonville shopping center.

Experts estimate more than 25 thousand bees died there, possibly the largest recorded bee die-off in history.

All 55 of the trees have since been covered in nets. But more than a week after the first reports, there are still bees dying in the parking lot.

“It’s almost like they’re hanging on trying to get through…. whatever is on there is not good,” said Wilsonville resident Adria Condon.

In both cases, the bees fell from Linden trees that had been sprayed with a pesticide called Safari, which is safe for humans and animals but is deadly to bees and other insects.

“This particular pesticide isn’t just a residue on the surface. It gets taken into the plant, comes out in the pollen, in the nectar and it gets handed to bees and other pollinators basically on a platter,” said Mace Vaughan with the Xerces Society.

The Xerces Society is now working with lawmakers to implement some sort of ban on the chemical.

“Homeowners can be applying these products in their backyards and not even know it, so maybe it would be great if we could have a ban on the use of these for cosmetic purposes,” said Vaughan.

Investigators have confirmed the Wilsonville bees died as a direct result of this particular pesticide.

They are still awaiting results in the Hillsboro case.

City officials there say of the 200 trees they sprayed, only one tree seems to be causing problems.