By Marc Lutz
An annual 200-acre treatment limit on the U.S. Forest Service’s invasive plant management program in the 3.7-million-acre Wrangell-Petersburg district has the agency revamping and possibly expanding its efforts to eradicate foreign weeds that could damage the ecosystem and economy.
Since 2015, the Forest Service has been pulling, digging and spot-spraying plants like knotweed and canary grass that are not naturally occurring in Southeast. But project managers say it’s not enough and they need to increase the acreage and means of killing the plants.
The proposed actions would include no annual acreage treatment limit, coverage of both national forest and non-national forest lands, treatment of emergent vegetation and treating aquatic formations of weeds.
On Wrangell Island alone, invasive plants are distributed over about 760 acres, said Joni Johnson, a forest ecologist.
“The invasive species that have a moderate or higher invasiveness ranking and are most prevalent on Wrangell Island include knotweed, the orange and yellow hawkweeds, oxeye daisy and reed canarygrass,” Johnson said. “All but knotweed are commonly found on Wrangell Island, but the knotweed is extremely invasive.”
Johnson said the weeds make their way into the environment mainly because humans bring them in. Ornamental plants like European mountain ash and knotweed “escape” and spread naturally. Other seeds will come in via hay or by adhering to clothing.
Whatever means by which the weeds spread, the results can be devastating.
“For example, the aquatic elodea plant that is spreading in the Anchorage, Mat-Su, Kenai and Fairbanks lake systems could impact the sockeye fishery to the tune of $159 million a year,” Johnson said. “Knotweed (fishery damage) in the state of Washington is estimated at $9.3 million a year.”
Most of the project area in the Wrangell-Petersburg district, according to the Forest Service, “is undeveloped and primarily used for dispersed recreation activities. Viewing scenery and wildlife, boating, fishing, beachcombing, hiking and hunting are the primary dispersed recreation activities that take place within the project area.”
She said ecological harm happens when the weeds “out-compete” the native plants.
“When reed canary grass or knotweed form a dense thicket along the stream bank, the plant community that contributes leaf litter to the aquatic invertebrates is no longer present and changes can occur to the food chain for fish species,” Johnson said. “Reed canary grass can also change physical processes in stream channels as the root mass can anchor substrate and change how sediment is moved and deposited.”
By adding broadcast spraying to the ways in which herbicides are applied, the Forest Service reported it would be able to cover a greater area, thereby killing more invasive plants at a lower cost. The biggest opposition the agency has faced from the public in expanding its coverage is the use of herbicides.
The herbicides used include “aquatic formulations of glyphosate and imazapyr, and aminopyralid,” the report states, and “application rates for all three herbicides would be at or below the maximum rate stated on the product label.”
To learn more about the proposed changes and what the entirety of the project entails, visit fs.usda.gov/project/?project=59576.
Objections to the enhanced effort against the plants are due by April 9, but may be submitted only by persons who participated in earlier comment periods on the proposal.
Johnson said anywhere from one to four Forest Service staff are typically involved when applying herbicides, but community members interested in participating in control efforts can contact the Wrangell District office. She also said control efforts tend to focus on areas where the Forest Service knows the weeds are growing.
“Granted, we are more likely to visit these locations, so there are always the exceptions,” she said. “If you do know of any exceptions, please let your Forest Service staff know.”