Article image

Invasive aquatic weed is spreading rapidly in the northeastern U.S.

The northeastern United States is witnessing a growing environmental challenge as a notorious aquatic weed, known as northern hydrilla, expands its reach.

Initially confined to the Connecticut River, recent studies have shown this invasive species is now populating multiple waterbodies across Connecticut and even reaching into Massachusetts.

The ecological threat of northern hydrilla

Northern hydrilla is known for its rapid growth, which can form dense canopies that hinder recreational activities like boating and fishing. More critically, its unchecked spread poses a significant threat to native plant and animal species.

This subspecies also carries a bacterium that produces a neurotoxin linked to fatalities in bald eagles and waterfowl, highlighting its dangerous ecological impact.

Study lead author Jeremiah Foley, an assistant agricultural scientist with the Connecticut Agricultural Experiment Statio, expressed significant concern about the expansion of northern hydrilla.

“The spread and establishment of yet another hydrilla subspecies in the United States is alarming. Especially alarming is the negative impacts that this invasive aquatic weed can have on native aquatic and non-aquatic plant and animal species, and how quickly it’s spreading,” said Foley.

Recent discoveries and the need for vigilance

Northern hydrilla (Hydrilla verticillata subspecies lithuanica) remained undocumented outside the Connecticut River until 2022. However, by the end of 2023, this invasive weed had been detected in six additional locations.

These sites are frequently near boat-launch ramps, indicating a potential route for the spread of northern hydrilla.

“Significant costs are already associated with the impact and maintenance of the prior two subspecies established in the U.S. since the 1960s and 1980s,” said Foley.

“The discovery of Hydrilla verticillata and its subspecies lithuanica in the Connecticut River and the breadth of the current infestation represent a significant ecological invasion event with potentially far-reaching implications.”

Popular fishing spots such as East Twin Lakes, Amos Lake, and Congamond Lakes, which regularly host fishing tournaments, are particularly at risk.

Moreover, the movement of boats from infested waters to uninfected areas during these tournaments poses a high risk of spreading northern hydrilla.

Foley highlighted the specific dangers associated with these movements: “Of particular concern are tournaments that involve travel from infested waterbodies to non-infested ones.”

The crucial fight against northern hydrilla

Given the situation, Foley emphasized the importance of research into how angling tournaments might contribute to the spread of hydrilla.

“Management efforts should prioritize early detection and prevention strategies, such as increased monitoring at boat-launch ramps and enhanced education for boaters to mitigate the spread of this invasive species.”

The battle against the spread of northern hydrilla is crucial for preserving our aquatic ecosystems.

The detailed findings and recommendations from this study are available in an article published by Cambridge University Press in a journal of the Weed Science Society of America.

The publication not only raises awareness but also serves as a call to action for all stakeholders involved in the health of our water bodies.

More about northern hydrilla 

Northern hydrilla, also known as Hydrilla verticillata, is a submersed aquatic plant that has garnered attention due to its invasive nature and rapid growth in freshwater environments. Originally native to Asia, it has spread across various regions including North America and Europe, thriving in lakes, rivers, and canals.


This plant is characterized by its dense, mat-like growth which can dominate water bodies, blocking sunlight and depleting oxygen levels, thus outcompeting native species and altering aquatic ecosystems. 

Hydrilla has slender stems that can grow up to 25 feet long, depending on water depth, and it features small, pointed leaves that grow in whorls of four to eight around the stem. It also reproduces prolifically not only through seeds but also vegetatively through fragments, tubers, and turions, making it particularly difficult to control once established.

Management of northern hydrilla 

Due to its aggressive growth and resilience, managing hydrilla often involves a combination of mechanical harvesting, chemical herbicides, and biological control, such as introducing specific fish species that feed on it. Despite control efforts, hydrilla remains a challenging and costly invasive species to manage in affected water bodies.

The study is published in the journal Invasive Plant Science and Management.


Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and


News coming your way
The biggest news about our planet delivered to you each day