• The goal of reducing aquatic weed abundance in the Tahoe Keys by 75 percent was adopted in 2024. Approximately 90 percent of the total wetted surface of the lagoons are covered with weeds during the peak of the season.
• The Control Methods Test is now it its third year. Data from tests will inform the long-term management of the weed infestation in the Tahoe Keys.
• The goal of year two tests (2023) is to maintain the year one weed ”knock-back” using entirely non-chemical Group B methods, such as UV light treatment, bottom barriers, and diver-assisted suction harvesting. No herbicides were applied in 2023.
• As of 2020, there were an estimated 502,112 cubic yards of aquatic invasive plants in Tahoe Keys, representing a 38.9 percent of volume of the Tahoe Keys.
• Additional details on the work to address the infestations in the Tahoe Keys and the latest updates on the control methods test is available at tahoekeysweeds.org.

Relevance

Maintaining the biological integrity of Lake Tahoe’s nearshore environment is a longtime goal of resource managers in the region and has been set forth in a variety of planning documents. Submerged aquatic vegetation is an important biological component within Lake Tahoe’s nearshore context.

The Tahoe Keys is the largest and most persistent population of aquatic weeds growing in the Region, infesting over 172 acres of waterways. Due to aquatic invasive plants’ proclivity to spread and establish new infestations through fragmentation throughout connected waterbodies, source fragements from the Tahoe Keys are a threat to the rest of Lake Tahoe.  

Two aquatic invasive plants, Eurasian watermilfoil (Myriophyllum spicatum) and curly-leaf pondweed (Potamogeton crispus), are the primary targets of the threshold standard. Aquatic invasive plants, when left unchecked, can impact water quality, fish and wildlife habitat conditions, recreational fishing, human and animal health, vessel navigation, and the recreation values of water bodies.

The goal aligns with the management categories that are utilized by the Lake Tahoe Aquatic Invasive Species Coordinating Committee and conveys the reality of long-term management of aquatic invasive species.

Human and Environmental Drivers

Non-native species have been both intentionally and unintentionally introduced to Lake Tahoe over the last 150 years. Habitat modification such as channelization and modification of the Upper Truckee Marsh for the Tahoe Keys also created micro-environments within the lake that may be more suitable for colonization by AIS. Climate change further threatens to alter the lake’s physical environment, with the potential for making further AIS establishment more likely.

In January 2022, both TRPA and Lahontan Water Board approved the Control Methods Test, and the three-year test is now underway.  Data from tests will inform a long-term management plan for the weed infestation in the 172 acres of the Tahoe Keys lagoons.

EIP Action Priorities

• Prevent, Control, or Eradicate Aquatic Invasive Species

  Projects aim to reduce and eradicate populations of invasive aquatic weeds.

EIP Indicators

• Acres of Invasive Species Inventoried
• Acres Treated for Invasive Species

Example EIP Projects

• Tahoe Keys Lagoon Aquatic Weeds Control Methods Test Implementation

Local and Regional Plans

• Aquatic Invasive Species Action Agenda 2021-2030

  The Lake Tahoe Region Aquatic Invasive Species Action Agenda 2021-2030 implements a well-funded, comprehensive, robust, simultaneous, science based, and aggressive suite of AIS control actions.

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