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Eyes on the Keys

The Tahoe Keys invasive weed management plan looks to use herbicides
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Public Input

• There will be an expert panel on herbicides that coincides with the TRPA meeting in February or March. For more information, visit

• Lahonton Regional Water Quality Control Board will most likely discuss the plan at its January board meeting. For more information, visit

• To review the Tahoe Keys Integrated Weed Management Plan, visit

The Tahoe Keys has long been considered Lake Tahoe’s number one environmental disaster, having been developed on the mouth of the Upper Truckee River in the 1960s. The 760-acre development, which includes 11 miles of lagoons and channels, is what environmentalists point to as the reason environmental protection was needed at Tahoe. But the main problem affecting the Keys today is a problem that threatens the entirety of Lake Tahoe — aquatic invasive weeds.

While a plethora of programs have been implemented by various agencies around the lake to prevent the infestation of invasive species, nowhere is the problem as troubling or complicated as South Lake’s Tahoe Keys. Roughly 90 percent of the 172 acres of the Keys’ waterways are infested with Eurasian watermilfoil and curlyleaf pondweed, which were introduced in the 1980s. The aggressive weeds interfere with native species, harbor non-native fish species, create mosquito habitat, and interfere with boating and other recreational activities. They also can — and have — spread to other parts of the lake. The Tahoe Keys Property Owners Association, which includes more than 1,500 homeowners, has been working for 25 years to combat the issue, but have been unsuccessful at controlling the problem.

“Nowhere else in Lake Tahoe is the problem of invasive and nuisance aquatic weeds as great as in the Tahoe Keys, where shallow, protected waterways provide ideal conditions for infestation,” states the website for the Key’s weed management plan. “We must take action to reduce and manage aquatic invasive weeds before they spread.”

The Tahoe Keys Integrated Weed Management Plan looks to address the aquatic invasive weed issue by initiating a method never before used at Lake Tahoe — the use of herbicides. The draft plan, which was released in August, includes using mechanical harvesters, bottom barrier mats, and diver-assisted suctioning, but also emphasizes the use of chemicals to combat the weeds. The plan proposes using the methods simultaneously over a five-year period, in varying degrees. The hope is that by using the proposed methods, the Keys’ weed problem will be reduced by 75 to 80 percent in five years. And the scientists involved with the plan believe the only way to achieve that goal is with herbicides.

“Herbicides knock the plant down to a manageable level. They are so much more efficient and effective than other methods,” said Lars Anderson, a former U.S. Department of Agriculture aquatic weed specialist who co-authored the plan as a consultant to the association. “Herbicides are not all the same. We researched for the type of plants that are in the Keys.”

Joel Trumbo, a senior environmental scientist with the California Department of Fish and Wildlife, who has been the agency’s integrated pests management coordinator for 25 years, advising on approximately 60 projects statewide each year, believes herbicides are needed in the Keys.

“The chance of meeting the project’s objectives without the use of herbicides would be really low,” said Trumbo, who was one of five independent experts who reviewed the plan. “It is a well thought-out plan. It is looking at all options — both chemical and non-chemical. It has the high potential to reach their goals.”

Even Dr. Charles Goldman, the former director of the Tahoe Research Group and UC Davis limnologist, whose more than 40 years of scientific findings at Lake Tahoe served as the underlying basis for nearly all major policy decisions regarding water quality in the Tahoe Basin, supports the use of herbicides in the Keys.

“For many years, I have believed that the use of herbicides is warranted in the case of the Keys, although in general I am not keen on the use of herbicides,” Goldman wrote in an Aug. 11 letter to the authors of the management plan. “I hope the necessary permits can at last be obtained to use herbicides in the Keys. I have recommended this in the past with the plastic damming of two outlets to allow the chemicals to decompose to acceptable levels.”


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February 14, 2019