State to begin emergency effort to kill invasive weed in Anchorage's Lake Hood

Herbicide applications are scheduled to start Friday to rid Anchorage's Lake Hood -- the nation's busiest floatplane center -- of a newly discovered invasive plant infestation, a state official said.

The work to combat elodea at Lake Hood Seaplane Base in Anchorage will start quickly, thanks to an emergency authorization from state environmental officials and other speedy permitting and funding, said Heather Stewart, invasive weeds and agricultural pest coordinator for the Alaska Department of Natural Resources.

The Alaska Department of Environmental Conservation invoked its emergency authority last week to grant a special herbicide permit, and other authorizations are falling into place to allow DNR's invasive plants program to start the Lake Hood project quickly, Stewart said.

"We wanted to make sure we dealt with that as fast as we possibly could," she said.

Elodea, also known as waterweed, is a long-stemmed, leafy freshwater plant that thrives in cool waters and easily survives cold winters.

It grows quickly and can create tangled masses that crowd out native plants, according to DNR. It has already taken hold in several water bodies in Alaska. It was first found in the state in Cordova's Eyak Lake in 1982, and since then the plant has been discovered in spots as far north as the Fairbanks area and as far south as the Kenai Peninsula. It has also invaded water bodies elsewhere in the world, most notably Russia's Lake Baikal, the world's deepest freshwater lake.

Now that elodea has been found at Lake Hood, a discovery made early last month and confirmed with a follow-up survey, the concern is that it could be carried by floatplanes traveling from there to untold watery destinations.


Normally, applications of herbicide would require a public review process of at least 90 days, Stewart said. Any herbicide project using federal funds requires completion of an environmental assessment, meaning another public review process. But emergency permitting and funding from non-federal sources -- including a contribution from the Kenai Peninsula Borough, where officials are seeking to protect their own lakes from elodea -- has allowed the Lake Hood response to be much speedier than normal, she said.

A survey last month of the floatplane base -- which sprawls over two connected lakes, Lake Hood and Lake Spenard -- found that elodea growth was confined to just three areas, Stewart said. The elodea is still far outweighed by native vegetation, she said.

"It's actually not that widespread," she said. "That's a good thing because we really are getting it early in the infestation."

To get rid of the Lake Hood elodea, DNR officials have designed a project that is separate from a previously planned project to attack elodea in three other Anchorage lakes.

The DNR team plans to apply a quick-acting and strong herbicide, diquat, in specific trouble spots, Stewart said. That will be done with a hose system from a boat, she said.

The diquat is a "one-and-done thing," to be followed by applications of a longer-lasting but slower-acting herbicide, fluridone. The first application of fluridone will be in liquid form, through the hose system, and will cover the entire lake, Stewart said. It will be followed by an application of fluridone pellets, she said. The fluridone process is expected to take an additional three years, and that future work would require public review, she said.

Meanwhile, DNR is on track to start applying pesticide next month as part of its already planned elodea eradication project at Anchorage's Little Campbell Lake in Kincaid Park and nearby Sand Lake and DeLong Lake, Stewart said.

At those lakes, DNR will use only fluridone, and plans low concentrations and multi-year applications. The lakes are popular recreation sites, so the program is designed to target elodea while protecting swimmers, boaters and their pets, Stewart said. The project targeting those lakes is funded by the U.S. Fish and Wildlife Service, she said, so it went through a formal public review and environmental assessment process.

Fears that elodea had spread to another busy floatplane base in Anchorage, Campbell Lake, were not confirmed. A state team surveyed the lake on Tuesday and did not find the plant there, Stewart said.

However, the survey did find that native vegetation had grown rapidly, enough to raise concerns about those plants getting tangled with planes' floats.

The summer's high temperatures, the region's low snowpack and various lakes' low water levels have created conditions encouraging rapid growth of aquatic plants, Stewart said. "That allows native vegetation to grow a lot more substantially than it would in a normal year," she said.

Yereth Rosen

Yereth Rosen was a reporter for Alaska Dispatch News.