Herbicides may be used on invasive species in Tahoe Keys

The underwater scenes could be straight out of "Creature of the Black Lagoon." Long feathery tendrils of green plants, growing at alarming rates in the Tahoe Keys and attracting fish not before known in the crystal blue waters of the lake.

The plant described here is better known as the Eurasian Watermilfoil. It is joined by another nuisance non-native plant, the curlyleaf pondweed, in creating problems in the waters of the Tahoe Keys.

In a packed house meeting on Tuesday night, the Tahoe Keys Property Owners Association (TKPOA) presented their plan of attack on the non-native species of plants that are taking over the Keys. If something is not done soon, they invasive species will continue to spread to Lake Tahoe.

That was the message presented by a panel of five experts gathered by TKPOA to explain the proposed Integrated Weed Management Plan (IWMP). Dr. Lars Anderson, an expert on waterweed solutions, was joined by Dr. Joe DiTamaso of U.C. Davis, Dr. Sudeep Chandra of UNR, Dr. Joel Trumbo of the California Department of Fish and Wildlife, Dr. Kurt Getsinger of the U.S. Army Corps of Engineers and Dr. Pat Akers of the California Department of Food and Agriculture.

As they shared their perspectives on the IWMP, their message was basically the same: Use science based research to protect the integrity of the lake, and the use of herbicides will be the most effective way to accomplish this.

Currently, there are five weed harvesters and four work boats with a staff of 12 pulling out the invasive weeds at a cost of about $400,000 per year.

There are many problems with this method. Besides being costly, harvesting the weeds isn't selective and many native plants are also pulled out. As soon as the weed is broken apart, fragments of the plant float away and start growing in another location, creating an unending issue of re-population.

TKPOA wants to get rid of the weeds with a five year adaptive management plan which is outlined in the photos in this story. They want to use a combination of herbicides, harvesting and partitions to remove the threat. They called these their "tool box" of answers to the weed problem, not relying on any one type of eradication and including both chemical and non-chemical methods.

Harvesting after using herbicides doesn't pose the same issues as just harvesting does today. The dead plants cannot spread living fragments through the water.

To be effective, there needs to be a group effort among the six primary landowner groups, including the Tahoe Keys Property Owners Association, along with the Tahoe Keys Marina, a commercial business center, the nonprofit Tahoe Keys Beach and Harbor Association, privately-owned Lake Tallac, and the nonprofit California Tahoe Conservancy, all along 11 miles of interconnected waterways.

Many in attendance were concerned about the use of herbicides in the Keys, which could then make its way into the lake and water supplies. The panel said that the risk is low as the aquatic herbicides that would use don't hang around after they attack the plants and have been safely used for infestations across the country.

The ecological threat these invasive weeds pose for Lake Tahoe is huge. The weeds thrive, they attract warm water fish and a whole new change of habitat is created.

"Action needs to be taken quickly to protect the integrity of the lake," said Dr. DiTamaso.

A lot is known about the items in the "tool box" since the invasive weeds are not only a problem in Lake Tahoe. Lakes in Washington, Oregon, Idaho, Michigan, Minnesota and Wisconsin have all had to deal with watermilfoil through the use of herbicides.

How did this invasive, non-native weed even end up in the lake?

The experts all say household aquariums are to blame.

The Eurasian Watermilfoil is a common plant used in aquariums, and many people dumps their tanks into the water, thinking they're adding natural things back into the water.

Dumping of little goldfish into the lake has resulted in documented photos and reports of large goldfish now making their home in the weeds of the Keys. Besides these non-native fish there has been a growing population of Bluegill, bass, perch and catfish. The authorities said that most likely these all entered Lake Tahoe with fishermen's bait. Minnows and other bait bought elsewhere are brought to the lake, thus introducing non-native fish into the lake. Non-natives then take over and native fish numbers start to dwindle.

This is the same problem with the invasive weeds, they take over and natives don't stand much of a chance.

Going forward, it will be education that saves the lake by teaching people what causes invasive species being introduced into the lake. The boat inspection stations are helping as well.

TKPOA posted the weed plan on line Tuesday and can be viewed here. The next step is to present it to Lahontan Water Control Board in October of this year, then to TRPA by the end of 2015.