CRWP experiments with mowing invasive grass

Mowing could reduce amount of herbicide necessary to eradicate reed canary grass

Invasive plant technician Samantha Vargas helps manage a stand of reed canary grass in Cordova. Photo courtesy of Ashley Taylor

Battling an extremely difficult-to-kill invasive plant, conservationists are trying a new tool: the Weedwacker.

Reed canary grass, which can crowd out native grass species and obstruct salmon spawning, cannot simply be pulled up like some other weeds. Unlike dandelions with their thick taproots, reed canary grass sends forth a web of many small roots that can generate new shoots if they are not completely removed. Because of this, mowing is not enough to destroy an infestation of the grass.

However, Copper River Watershed Project conservationists are hopeful that combining mowing with herbicide will allow Cordova to more quickly rid itself of the plant.

“Mowing it is not going to treat it — it’s going to assist us in our other treatment methods,” said Chantel Adelfio, CRWP invasive plants coordinator. “It’s going to limit seed head production and it’s going to limit the amount of herbicide we have to put on the plant.”

The CRWP has recently clipped the seed heads off stands of reed canary grass around Cordova, and is currently mowing some stands. Other stands will be left unmowed to determine whether mowing before applying herbicide is an effective technique.

Targeted use of the herbicide Roundup Custom for Aquatic and Terrestrial Use eliminated 77 percent of reed canary grass around Cordova between 2018-2019, the CRWP announced Aug. 29, 2019. If the grass can be eradicated in Cordova, it’s unlikely that it will return, Adelfio said.

Advertisement

Herbicide application at reed canary grass stands around Cordova is tentatively scheduled for August. Herbicide is typically used around autumn, the season during which leaves most actively move nutrients to the roots, Adelfio said.

Although the coronavirus pandemic has prevented conservationists from doing fieldwork in large groups, smaller crews have still been able to carry out their work effectively, Adelfio said. The online service Anecdata has allowed community members to participate in the project by reporting stands of invasie plants.

Advertisement