$250,000 Tahoe Keys weed management plan includes herbicides
August 15, 2015
SOUTH LAKE TAHOE, Calif. — The Tahoe Keys has introduced a new plan of attack on its aquatic invasive plant epidemic, which includes herbicides and an adaptive strategy.
The $250,000 plan, sponsored by the Tahoe Keys Property Owners Association (TKPOA), released on Tuesday for comment, tackles an issue that other methods during the past 25 years have failed to address to remove non-native invasive species that choke parts of the Tahoe Keys lagoons.
Scientists and experts who vetted the science of the plan discussed it Tuesday night at the South Tahoe Public Utilities District.
The panel included: Joe DiTomaso from U.C. Davis, Patrick Akers from the California Department of Agriculture, Kurt Gestinger from the Army Corps of Engineers, Joel Trumbo from California Department of Fish and Wildlife, and Sudeep Chandra, a limnologist and professor at University of Nevada, Reno.
Specialist Lars Anderson and Tahoe Keys Water Quality Committee helped developed the plan during more than two years.
All five panelists agreed the plan provided the best hope to manage the problem in the Keys.
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"The problems in the Keys are significant and that action needed to be taken, and quickly," DiTomaso said. "It's the potential to spread to other parts of the lake that we are conceded about."
Eurasian milfoil and curlyleaf pondweed, introduced at different times, have grown to a point they have suppressed the growth of natural plant species. The plants also act as a breeding ground for non-native warm water aquatic life like the bluegill, goldfish, catfish and bullfrogs.
The plan also addresses coontail, a native Tahoe plant that grows in abundance.
The plan, which intends to be implemented in 2017 after its final environmental review, will use herbicide over the course of five years in conjunction with other methods like bottom barriers to reduce and manage the plans.
The Keys has its own habitat, almost separate from Lake Tahoe. Three main lagoons — Lake Tallac, Main Lagoon and Marina Lagoon — two channels and its canals are warmer and shallower than Lake Tahoe, making it a perfect breeding ground for the invasive plants and fish.
A boat tour by the panelists, TKPOA staff and board members and local environmentalists Tuesday morning presented a concrete view of the problems.
Curlyleaf pondweed and Eurasian milfoil clustered in different parts of the Tahoe Keys lagoons, creating the impression of an underwater jungle. In some areas, goldfish, bluegill and catfish darted through the mesh of plants.
Harvesters and workboat crews went about trying to remove portions of the weeds and collecting fragments. Fragments, according to the experts, become a problem because they can quickly create new clusters.
According to John Larson, TKPOA's board president, harvesters have had mixed results and become cost-prohibitive. TKPOA's attempts have cost $400,000 a year. Harvesters also generate 4,000 fragments per acre harvested.
University of Nevada, Reno, according to Chandra, has a boat routinely used by the California Department of Fish and Wildlife to capture non-native fish using electrocution.
Implementing the plan would provide a chance to restore the natural ecosystem, the panelists agreed. Reducing the non-native species would give native fish a chance to thrive, restore at least some water clarity and recreational options for Tahoe residents.
Larson said estimates could be at least $500,000 to implement the plan but the Keys would see long-term savings from reduced harvesting efforts. However, he stressed that the plan still is in its early stage so costs haven't been established yet.
Most of the questions posed to the panel Tuesday night had to do the safety of using herbicides.
Larson said that TKPOA will be monitoring the use of herbicides to make sure they don't affect the Tahoe Keys groundwater wells. Should the wells be contaminated, they would be taken offline and switch over to the South Tahoe Public Utilities District system.
Ultimately the decision to use herbicides will be made by the Lahontan Regional Water Quality Board, which has final say on anything that impacts groundwater sources in the California side of the Lake Tahoe basin.
Panelists said the herbicides were thoroughly vetted and could target certain plants while others remained unaffected. Only 14 have been federally approved.
Trumbo, from Fish and Wildlife, said that herbicides are harmful to plants, while they have less or no risk to non-plant life.
Chandra, whose research has been focused largely around Lake Tahoe, said it was a struggle at first to accept the use of herbicides as an option.
"Use of herbicides is not an easy decision, particularly since this is Lake Tahoe," Chandra said. "But we do agree that we need as many tools as possible."
The panel also agreed that eradication wouldn't be possible, only long-term management.
"Control means reducing it to the point of insignificance," Trumbo said.
Larson, TKPOA's board president, said the plan also will have to involve the Tahoe Keys eight landholders, including the owners of Lake Tallac, Tahoe Keys Beach and Harbor Association, Tahoe Keys Marina, the California Tahoe Conservancy and Tahoe Keys Village. Larson said not all are on board.
"We all have to find a way to work together," Larson said.
People can comment on the plan until Sept. 15 online at http://www.keysweedsmanagement.org.