Dead and dying ponderosa pines line Highway 20 near Sisters, Oregon.

Dead and dying ponderosa pines line Highway 20 near Sisters, Oregon.

Ryan Brennecke, The Bulletin/AP

The U.S. Forest Service was scheduled to present a plan Monday in Sisters to log trees that the Oregon Department of Transportation accidentally killed along a scenic drive. The culprit is an herbicide that state regulators still allow for roadside weed control.

The Forest Service says it needs to log as soon as possible along a 12-mile stretch of scenic road corridor through the Deschutes National Forest. Some of the trees to come down are hundreds of years old.

“It’s a public safety issue … you just never know when a tree is going to go,” said Forest Service spokeswoman Kassidy Kern.

The herbicide Perspective is behind the die-off. An ODOT contractor in Jefferson County applied it for years to control weeds and minimize fire risk along Highway 20. Trees absorbed the chemical aminocyclopyrachlor through their roots and began to slowly die. 

ODOT’s Peter Murphy says the agency is no longer using Perspective. But the Oregon Department of Agriculture has not restricted its use in response to tree deaths.

ODA spokeswoman Andrea Cantu-Schomus said in a text message: “ODA is collecting information on how widespread the damage might be, and is evaluating possible restrictions to prevent future damage to valuable tree species. ODA does intend to implement protective measures in the near future.”

The Forest Service hopes to log the standing dead and dying trees before winter.