Fighting weeds along the Metolius River

Depending on appropriate weather conditions, the Deschutes National Forest will apply herbicides to invasive plants within an area adjacent to the Metolius River and the Metolius River Trail October 1-5.

The Sisters Ranger District will use two herbicides (Aquamaster and Polaris) to treat invasive non-native ribbongrass, reed canarygrass and yellow flag iris on about 1.5 acres of the Metolius River. Treatments will take place in select locations from just upstream of the confluence with South Fork Lake Creek downstream past Gorge Campground.

The method of treatment will be spot applications with a backpack or hand-sprayer. It involves application of herbicide to foliage of target invasive plants to minimize effects to native plants. The applied herbicides will dry within an hour of being applied and do not pose a risk to human or animal health under the concentrations being applied, the Forest Service reports.

The Metolius River Trail will remain open during treatment, but the public should remain on the trail during active treatment operations and keep dogs leashed.

Ribbongrass, reed canarygrass and yellow flag iris are aggressive invasive plants that are overtaking native sedges, wildflowers, and shrubs within the river's riparian habitats. Forest Service Public Affairs Officer Kassidy Kearn reports that, "These invasive plants out-compete most native species and present a major challenge in protecting the unique native vegetation and habitat of the Metolius River. Restoring and protecting the Metolius Wild and Scenic River and its values including fish, wildlife, water quality, ecology, scenery, and cultural values is a priority of the Deschutes National Forest. This action, in addition to others, will move that restoration effort forward."

The two herbicides being used were approved through an environmental analysis in 2005 and a supplemental environmental analysis in 2012, the Forest Service reports.

According to the Deschutes National Forest, experimentation with alternative methods of control proved unsatisfactory. Covering areas with black plastic for two years

(known as solarization)

and hand-pulling showed that any root not completely removed continues to reproduce, so neither control method is feasible given the size of the infestations.