A weed killer used to manage plants along U.S. Highway 20 left the Deschutes National Forest with hundreds of standing but dead ponderosa pine trees. While trees in serious danger of falling onto the highway can be chopped down, a full-scale effort to remove them may not begin until 2019.

The U.S. Forest Service is seeking public comment on a plan to remove the trees, along an approximately 12-mile segment of the highway near Sisters. Forestry officials believe the trees were killed by an unhealthy dose of Perspective, the brand name of a herbicide used in the area for several years.

The herbicide, administered by contractors working for the Oregon Department of Transportation, was intended to kill the broad-leaf weeds and other flammable plants, but also killed more than 1,000 trees — the majority of which are ponderosas — in the surrounding area.

“The whole point is safety; that’s the irony of it,” said Peter Murphy, spokesman for the Oregon Department of Transportation.

Many of the dead trees are mature ponderosa pines with the potential to fall into the nearby roadway, according to Brent Oblinger, forest pathologist for the U.S. Forest Service.

“There can be thousands of cars that travel that segment each day,” Oblinger said.

Eliminating weeds along the road is an important fire prevention tactic. Dry roadside grasses are a common cause of fire in Central Oregon, as they can easily ignite from a spark from an idling car. Because of that, Murphy said the agency has an agreement with the Forest Service to manage roadside vegetation on roads that run through federally managed land.

Murphy said ODOT applies different treatments to different areas of road, depending on the terrain. At the time the herbicide was first used in the area, about 2013, Perspective was still approved to treat sections on forestland and was not listed as dangerous to ponderosa pines, according to Oblinger.

The Forest Service no longer uses the weed-killer, which is now produced by Bayer and contains aminocyclopyrachlor, in Oregon and Washington.

“When it comes down to vegetation, there’s no one-size-fits-all solution,” Murphy added.

Mike McHaney, public works director for Jefferson County, which was selected as the contractor on the project, said the Forest Service instructed the county agency to use Perspective.

McHaney said the public works department handles weed maintenance for other governments as part of an exchange of services, and has used Perspective on other roadways in Central Oregon. However, he added that the proximity of the trees on the section of roadway near Sisters, along with a particularly dry winter in 2014 that prevented the pesticide from seeping into the soil properly, exacerbated the effect of the herbicide on ponderosa pines.

By 2014, the Forest Service had noticed that something was wrong. Oblinger said employees began to notice browning foliage and other symptoms in trees along the road. Upon closer inspection, Oblinger noticed abnormal growth in stems and discolored crowns.

Not every tree in the area was affected, but many are dead or dying. Because the trees absorb the weed-killer through their root system, Oblinger said there’s no remedy for the trees once they absorb it.

Michael Keown, environmental planner for the Sisters Ranger District of the Deschutes National Forest, estimated that about a thousand trees could be affected.

“More and more trees are flagging and dying,” he said.

In December 2015, ODOT and the Forest Service held a joint meeting to take stock of the situation.

Oblinger said ponderosas become more likely to fall once they’ve been dead for five years because the trunks have decayed. Murphy said the transportation department considers standing dead trees within 150 feet of roadways to be potential hazards.

While Murphy said ODOT has discretion to knock down trees that threaten roadways, a more thorough project needs to run through Forest Service channels.

The Forest Service’s project would knock down and remove dead and dying trees for use in the forest products industry, as well as for stream restoration and habitat management, according to Keown.

Keown added that the agencies were targeting spring or fall to complete the project, given how busy Highway 20 gets during the summer. While Murphy said the project could get underway as soon as October, Keown was less optimistic.

“If we did implement the project, it would likely be next spring,” he said.

— Reporter: 541-617-7818, shamway@bendbulletin.com

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