Cornell Cooperative Extension

Tompkins County

Hydrilla FAQ

Below are some of the most frequently asked questions and concerns about hydrilla and the fight to eradicate it from the Cayuga Lake Watershed.

FAQ:

CAYUGA LAKE SPECIFIC:

What is hydrilla?

Hydrilla is one of the most aggressive aquatic plants to invade North America. There are two biotypes of hydrilla, monoecious and dioecious hydrilla. New York is now infested with monoecious hydrilla, and if it is not contained there is a very high chance that it will spread to a vast network of interconnected water bodies in New York, the Great Lakes, and more. It is a hardy plant that can thrive in many different conditions and is spread easily through fragmentation of the plant. Hydrilla is both harmful to the native ecosystem as well as to the local economy.

Read more...

What does hydrilla look like?

Hydrilla has long, slender stems that can grow up in depths of up to 30 feet. It usually has between 4-8 small, pointed leaves arranged in circular whorls along the length of its stem. The edges of the leaves are serrated. As the plant grows it forms a mat throughout the water column, blocking sun and restricting water flow. The most distinguishing part of the plant is the tuber, which can be found a few inches below the sediment. Read more...

How did it get the the USA?

In the US, hydrilla's first documented appearance in the wild was in Florida. A dealer for tropical fish and aquatic plants in Missouri imported hydrilla from Sri Lanka, thinking he was getting a species of anacharis, a green plant commonly sold for aquariums. He sent some to a dealer in Tampa, Florida, who was not impressed with the plants. The dealer's son put the hydrilla in a canal rather than in the trash. It grew lushly causing the dealer to decide the plants were worthwhile after all. He began selling them as "Indian Starvine." Other deals followed suit, growing the plant in Florida canals before selling them for the aquariums. The dumping of aquaria and boats on boat trailers then moved hydrilla farther afield.  Read more...

Where else is hydrilla found?

Hydrilla can be found in many states throughout the United States. There are two types of hydrilla (monoecious and dioecious). Monoecious is found in northern states where the climate is colder, and dioecious plants are found in southern states where the climate remains more consistent.

Where is it from originally?

The hydrilla found in New York state is native to southeast Asia and was brought to the United States through the aquarium trade. From there it most likely hitchhiked on a boat allowing it to spread to many parts of the US. Read more...

How is  it different from other aquatic plants?

Hydrilla is known for being able to grow very quickly (up to a foot per day) and in many conditions (including low light levels and poor nutrient areas). Fragments of the plant are still viable and can reproduce, sprouting new roots and establishing new populations. Read more...

Why is it so bad?

Hydrilla is a very hardy plant. It is able to grow up to a foot a day in a wide range of water conditions. Fragments that get caught on boats and boat trailers can spread easily and establish new populations.

Hydrilla poses a serious ecological threat. Its ability to grow in various conditions gives it an advantage that allows it to out-compete native plants. Infestations of hydrilla can be harmful to fish populations as well. Large infestations can cause oxygen depletion zones which can lead to fish kills. Hydrilla can also cause algae blooms, leading to even more depleted oxygen levels.

Hydrilla also poses serious economic threats to communities surrounding infested waters. Hydrilla can reduce waterflow in canals, clogging waterways which can cause flooding, clog irrigation canals, and has the ability to damage dams and water plants. Clogged waterways make it difficult (and impossible if left unmanaged) for boats to travel through, which can lead to decreased tourism and can adversely affect anglers and fisherman. Recreational activities can also be hampered. Boaters cannot enjoy infested waters, swimming becomes more difficult due to the increased risk of drowning, and the adverse affects on fish lead to decreased fishing.

What are the ecological impacts?

Hydrilla poses serious ecological threats. Its ability to grow in various conditions gives it an advantage that allows it to out-compete native plants. Infestations of hydrilla can be harmful to fish populations as well. Large infestations can cause oxygen depletion zones which can lead to fish kills. Hydrilla can also cause algae blooms, leading to even more depleted oxygen levels. While the mechanisms are still not well understood,  blue-green algae grows densely on hydrilla creating algae blooms that are toxic to animals and people. Reports show high levels of Avian Vascular Myelinopathy (AVM) in areas with hydrilla populations.

What are the economic impacts?

Hydrilla also poses serious economic threats to communities surrounding infested waters. Hydrilla can reduce waterflow in canals, clogging waterways which can cause flooding, clog irrigation canals, and has the ability to damage dams and water plants. Clogged waterways make it difficult (and impossible if left unmanaged) for boats to travel through, which can lead to decreased tourism and can adversely affect anglers and fisherman. Recreational activities can also be hampered. Boaters cannot enjoy infested waters, swimming becomes more difficult due to the increased risk of drowning, and the adverse affects on fish lead to decreased fishing.

Questions about the herbicides:

Endothall and fluridone have not been found to be toxic to waterfowl and wildlife at the concentration being applied (3 ppm for endothall and 3-8 ppb fluridone). Studies have been conducted on mammals and birds and show no toxic effect. It has also been found that this concentration is not toxic to dogs, cats, or livestock incidentally exposed to the herbicide.

The use of water for human consumption is prohibited while concentrations of endothall are greater than 0.1 ppm. There are no restrictions against drinking, swimming, or fishing during the fluridone treatment.

Many of the native plants are not adversely affected by the treatment because they largely seed producers, and seeds are not affected by the endothall treatment.

Studies have been done to test endothall's effect on  largemouth bass reproduction, and results show no effect.

CAYUGA LAKE SPECIFIC

When was it found in Cayuga Watershed?

Hydrilla was first discovered in the Cayuga Inlet in August 2011 by a volunteer on board the Floating Classroom. It was later discovered in Fall Creek and the southeast corner of Cayuga Lake in 2013.

How did it get here

While we will never know for sure, most likely hydrilla arrived in the Cayuga Inlet on a boat trailer or boat. The nearest water body with boat access that has type of hydrilla we have ( monoecious) is the Potomac River.

Who is managing the eradication efforts?

The Hydrilla Task Force of the Cayuga Lake Watershed is responsible for managing the eradication efforts.

What is being done to eradicate hydrilla?

When hydrilla was found in the Cayuga Inlet in 2011, the Hydrilla Task Force of the Cayuga Lake Watershed was formed and began researching how to respond to the infestation. The Hydrilla Task Force developed The Cayuga Inlet Hydrilla Management Plan.

All treatment options were considered, and herbicide treatments were chosen as the best option. Because the inlet is part of an open water system and due to its size, herbicides seemed to be the only logical option. In 2011, the herbicide endothall(trade name: Aquathol K) was applied. In 2012, a combination treatment was done. An endothall treatment was done, followed by a fluridone(trade name Sonar) treatment was done. The same treatment was done in 2013, with an additional endothall treatment to Fall Creek. Hydrilla found in the southeast corner of Cayuga Lake was hand-removed and covered by benthic barriers. 2014 treatments involved endothall application to Cayuga Inlet and Fall Creek, followed by fluridone treatments in Fall Creek and Cayuga Inlet. A small scale physical removal was also conducted in Fall Creek in September 2014. Herbicide applications in 2015 were largely similar to 2014, with additional applications of fluridone pellets to a 30 acre treatment zone in the southeast corner of Cayuga Lake proper. Herbicide application in Cayuga Inlet was scaled back in 2016, with only fluridone being applied from July through September. No endothall application was conducted in Cayuga Inlet in 2016. Fall Creek received a similar treatment in 2016.

Water monitoring has been done throughout each of the treatments. Racine-Johnson Aquatic Ecologists has been conducting extensive surveys of the Cayuga Inlet, Fall Creek, and the southern end of Cayuga Lake.

Why use herbicides in Fall Creek and the Cayuga Inlet?

Because Fall Creek and the Cayuga Inlet are part of an open water system and due to its size, herbicides seemed to be the only logical and reasonable option. When hydrilla was found in Fall Creek in 2013, action had to be taken immediately. The herbicide treatments will continue, but other treatment options are being considered for certain sections of the infested area. Dredging the shallow areas or placing benthic barriers over infested areas may be possibilities.

Why not use herbicides in Cayuga Lake?

The patches of hydrilla found in the southeast corner of Cayuga Lake were small, discrete patches. The area was highly accessible because they were found in shallow waters, making it possible for trained divers to hand-pull the hydrilla from the area while keeping all fragments that broke off during the process easy to contain. The patches were small enough that benthic barriers were a good treatment option. Fall Creek and the Cayuga Inlet are small areas, where dilution of the herbicides would happen at a slow enough rate that the applications would still be successful. An enormous amount of herbicides would be needed to treat the patches in Cayuga Lake because the herbicide would be diluted so quickly. Read more...

Herbicide treatments are so expensive, why don't we just let it go and manage it?

Herbicide treatments are expensive, and to truly eradicate hydrilla from our waterways the treatments will need to continue for years ahead. But as seen in Florida, managing hydrilla is far more expensive and management is needed forever.

Ithaca's situation is unique in many perspectives. If the hydrilla infestation were left untreated, it could spread further up the lake, into the Erie Canal, and into the

Great Lakes making our localized a problem into an international problem. Tourism and taxes from waterfront properties generate about $4 million annually in tax revenues and sales. If the

Cayuga Inlet were to be closed, the local waterfront businesses would be at risk of being shut down. If left untreated, the Cayuga Inlet would be closed in as little as 5 years.

How did it get into Fall Creek?

In past years, floating fragments of hydrilla have been observed in the inlet, allowing some fragments to float into the lake. A prevailing northwest wind on Cayuga lake could have pushed some fragments back towards Fall Creek, where they established new colonies. It is also possible that fragments were transported via watercrafts (many canoes and kayaks launch out of Fall Creek). Read more...

How will it affect boating?

In the past, the Cayuga Inlet and Fall Creek have been shut down during endothall herbicide applications. In 2016, neither the Inlet or Fall Creek were shut down during herbicide application. The HTF does not anticipate needing to shut down local waterways for future herbicide applications.

If we do not continue to treat the hydrilla and allow it to spread, it will eventually overtake the waterways, which could force the closing of the Cayuga Inlet and Fall Creek.

Is eradication still feasible?

Since hydrilla was found in the Cayuga Inlet early, eradication is still possible. The Invasion Curve shows that we found hydrilla at an early enough point that we were able to provide public outreach, create a management plan, and begin taking steps towards eradication. Read more...

Where has the eradication of hydrilla been successful?

California has shown great success in eradicating hydrilla from their waterways. Other areas including Washington State have also had success. Read more...

If we reach a tipping point, what's next?

A tipping point is a time when eradication is no longer considered feasible, and other management options must be considered. If hydrilla spreads to the point where herbicide treatments and other treatments options are not worth-while, what happens next? It is important to realize that we are NOT at this point. Eradication is still very feasible. In fact, treatments to the Cayuga Inlet, Fall Creek, and the southeast corner of the lake are all progressing toward and are on target for eradication.

It can cost millions of dollars to manage hydrilla in states where eradication is no longer feasible. Florida spends up to $30 million annually just to keep the priority waters navigable. Eradication efforts in the Cayuga Inlet cost about $500,000 annually, and those costs only lasts until hydrilla is successfully eradicated.

Eradication clears hydrilla from all waterways, allows for all waterbody uses, and costs less in both the short-and long-term. Management protects fewer water bodies from hydrilla, provides limited uses for only priority waterways, and can cost millions of dollars annually, and those costs last forever. 

What can I do to help?

There are many ways to become a part of the solution. When using your boat, remember to clean off your boat and dispose of weeds properly. If you find a hydrilla suspect, report it! You can help by becoming a Hydrilla Hunter or a Steward from the Finger Lakes Institute Watercraft Steward Program. You can also volunteer to provide public outreach at the Hydrilla Farmer's Market stand. Keep an eye out for more volunteer opportunities.

Why aren't there more boat washing stations at launch sites?
Boat washing stations are expensive to purchase, operate and staff. Each portable washing unit is about $20K and would cost $20-40K a season to staff and maintain plus the expense of site preparation and drainage. Right now we are asking for hand removal of plant from boats. Some locations, such as

Treman Marina, have disposal stations for water weeds. For anywhere that does not have a washing station/disposal area, the best thing to do is remove all visible plant material by hand, put it in a garbage bag and throw it away (or let it dry out away from any water bodies). Cleaning your boat at home and letting it dry thoroughly between uses also helps. In addition, stay out of weedy areas especially in the areas known to have hydrilla. We are interested in finding funding for additional boat washing and disposal stations.

Last updated January 6, 2020

About Hydrilla