Contact

Sharon Anderson
Environment Program Leader
(607) 272-2292 ext 156
ska2@cornell.edu

Cornell Cooperative Extension
Tompkins County
615 Willow Avenue
Ithaca, NY 14850-3555
(607) 272-2292
tompkins@cornell.edu

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Home » Environment » Invasive Species » Fighting Hydrilla

Fighting Hydrilla

FIGHTING HYDRILLA IN CAYUGA INLET
Prepared by the Cayuga Inlet Hydrilla Task Force, in widespread consultation with others
Last update: 4 October 2011

I. THE BOTTOM LINE

The Cayuga Inlet was closed for about 2 weeks in mid-October , 2011 to allow the use of a herbicide to kill an extremely aggressive invasive plant, hydrilla, that threatens the ecosystem of the Great Lakes.  This decision has been recommended by a task force with representatives from the city, the county, the state, and Cooperative Extension, after consultation with local community members, businesses, politicians, and Inlet users.  Until the application of the herbicide, the City of Ithaca has been stronglydiscouraging the use of boats in the Inlet.

II.  WHAT IS IT AND WHY SHOULD WE BE WORRIED?

  1. One of the most aggressive aquatic plants to invade North America, called hydrilla, was found in the Cayuga Lake Inlet in Ithaca in early August 2011.  If it is not contained, it is likely to spread into a vast network of interconnected water bodies in New York State and beyond, including the Great Lakes via reproductive structures called turions. The NY Invasive Species Research Institute has provided a summary of information about hydrilla.

  2. It will cost about $91,000 (plus staff time and volunteer time) to contain hydrilla this year, and substantial investments will be needed for follow-up for the next 5 years or so to prevent a widespread infestation.  Left unchecked, the cost to eradicate hydrilla in the Inlet will rise dramatically.  States with widespread hydrilla infestations spend up to $30 million per year to contain hydrilla. 

II. WHAT DO WE KNOW ABOUT WHAT CAN BE DONE?

  1. Experience with hydrilla in California, Washington, Florida and elsewhere suggests we have a very narrow window of opportunity - a window of just a few weeks - to arrest hydrilla spread in the Cayuga Inlet.  Reproductive structures call turions are forming that will substantially increase the area of our local infestation and very likely carry the plant into the Lake.

  2. Both national experts on hydrilla and local resource managers/stewards agree that applying the contact herbicide endothall is the best way to reduce the potential for hydrilla spread this season.  See Hydrilla Treatment FAQ on this site for more information about endothall.

  3. The experts also agree that follow‐up actions will be needed for at least the next 5 years. But taking action now will provide a window of time to plan for that longterm followup.

  4. Are there alternatives?  The short answer is "no."  The longer answers:

    • There is no predator or natural mechanism ("selective biocontrol") that works for stopping hydrilla in an open waterway like the Inlet. Sterile carp have been used to stop hydrilla in water bodies that can be isolated, such as ponds;  they eat all vegetation, regardless of whether it is invasive or not.  But the Inlet cannot be isolated or contained.  Carp would be likely to get into Cayuga Lake, causing extensive habitat damage.
    • There is no mechanical or physical mechanism that is likely to work in the Inlet.Letting the water drain from ponds and other water bodies has been used successfully to kill and remove hydrilla.  But since hydrilla has been found rooted in the middle of the Inlet channel, the Inlet would have to be completely drained -- water from tributaries as well as lake water would have to be kept out of the Inlet channel.  In practical terms, this is not physically possible.
    • Covering the existing plants to cut off their supply of light? ("benthic barriers") can be effective for small populations.  However, we would need more than 9 acres of barriers for just the dense infestations already identified.
    • Hand harvesting can be used for small infestations in shallow water.  Our infested area is too large and in water that is too deep and murky to effectively use volunteers or contractors for this work.

III. WHAT IS BEING RECOMMENDED AND WHO IS DOING THE RECOMMENDING?

  1. The City of Ithaca is already strongly discouraging the use of boats in the Inlet.  Boat traffic of any kind, including keel boats, motor boats, kayaks, canoes, paddleboards, crew shells, and sailing dinghies, can cause fragments of the plants to break off.  These fragments can be transported to areas that are not currently infested and can sprout roots and establish new populations.  The City's paddle boat docks, the Farmers' Market dock and informal launches and the Treman Boat Launch have all been closed.  Any boats coming out of the Inlet should be thoroughly cleaned including trailers, engine water, bilge water, keels, etc. and kept dry for an extended period of time to insure that any missed vegetative matter is killed.  Car washes are a good place to clean boats and trailers.
  2. The Cayuga Inlet Hydrilla Task Force has recommended that the quick-acting herbicide endothall (trade name Aquathol) be used in the Inlet to stop the growth of hydrilla before it spreads its reproductive structures (called "turions") in October.
  3. As the relevant local agency, the Tompkins County Soil & Water Conservation district has applied for a DEC permit to apply the herbicide.  Formal notification of affected landowners occurred on 14 September 2011; the permit can be issued after 6 October 2011.
  4. Because the potential economic and ecological damage from hydrilla requires strong action, the City of Ithaca will ask the Sheriff of Tompkins County (who has authority over waterways in the county) to close the Inlet when the herbicide is applied.

IV. IS THE HERBICIDE SAFE?

Detailed sheet of information about the herbicide endothall (trade name Aquathol K) is available on this site.  Key items from that information follow:

  1. Endothall has been used for managing submerged aquatic vegetation for more than 50 years.  The particular form to be used in Cayuga Inlet has been registered with the U.S. government since 1960, with the most recent safety evaluation taking place in 2005.  Endothall has been used in Sodus Bay, Chautauqua Lake, numerous ponds in Westchester County and other water bodies in New York State.

  2.  The herbicide will be applied by a licensed and certified herbicide applicator, Allied Biological (http://www.alliedbiological.com), with extensive experience in New York State. The concentrations of Endothall that are toxic to humans and animals far exceed the amounts that will be encountered in Cayuga Inlet.  As a precaution, use of the water in the Inlet for drinking (including by animals or residents of the "Jungle" area) will be restricted for 14 days; signs and other outreach will notify dogwalkers, residents of the Jungle, and others of the restrictions.  There will be a one-day restriction on swimming and bathing in Cayuga Inlet, as a safety precaution.

  3. The restrictions on water use apply within 600 feet of the site of application.  The Bolton Point water intake is three miles from the Inlet.  It will be monitored carefully, but it is well outside the affected area.  Some lake house owners do draw their water from the lake, and will be notified; however, none of the lake houses are within 600 feet of the site of application, and all have access to municipal water lines.

  4. Endothall does not accumulate in the tissues of animals or fish.  There are no restrictions on catching and eating fish from the treated waters.

  5. The Tompkins County Department of Health, in cooperation with the City of Ithaca, will monitor endothall levels in the Cayuga Inlet once the herbicide is applied, again after 3 days, again after 7 days, and if necessary every 7 days after that until endothall levels are undetectable.

  6. There is no danger at all to people or animals onshore who do not come into contact with the herbicide or the water.

V. RESPONSES TO CONCERNS EXPRESSED BY THE COMMUNITY

  1. Isn't it too late?  Didn't I read that the herbicide needed to be applied by September? While an earlier application might have been preferable, any reasonable effort to limit the spread of hydrilla is valuable.  Applying the herbicide in October will still kill of much of the exposed hydrilla plant material, providing a window of opportunity for planning other eradication efforts next year.  Additionally, the high water events in September created turbid water and blocked some sunlight, slowing the growth of the plant.

  2. But hasn't plant material already spread into Cayuga Lake?  Hasn't hydrilla been around for a couple of years?  And this year, we've had huge flooding and waterflows through the Inlet in September. A careful investigation of the hydrilla plants by Robert Johnson, a former faculty member at Cornell's Department of Ecology and Evolutionary Biology and now with the consulting company Racine‐Johnson Aquatic Ecologists, and consultations with hydrilla experts around the country suggests that this is the first year of any significant hydrilla growth in Cayuga Inlet.  For more information about the infestation, see the "Science-based review to guide management" prepared by the New York Invasive Species Research Institute. Despite the heavy waterflows, ongoing observations during September suggest that hydrilla spread has been quite limited.  If pieces did break off and float into Cayuga Lake, the evidence is that the pieces flowed into deep water, where they cannot survive.  Prevailing winds and typical water patterns would have driven pieces back towards Stewart Park.  So far, no evidence of hydrilla has been found there or in Fall Creek. By closing the Inlet to boat traffic, the risk of breaking off pieces of hydrilla vegetation is dramatically reduced.  The NYS DEC has said that any efforts to control hydrilla, even if later than ideal, are still useful.

  3. What about all the boats that have been using the Inlet since August?  There is some risk that plant material has been moved out of the Inlet by boats or boat trailers.  Many boats and their trailers have received careful cleaning at stations established at Treman Marine Park and Johnson's Boatyard.  All boat owners are strongly encouraged to have their boats and trailers carefully checked before putting them back in the water in any location, especially other Finger Lakes.

  4. Why did it take so long to get the permit?  In other states, the herbicide might have been applied within days after the initial discovery in early August.  However, New York State laws and regulations established to safeguard state residents led to careful discussion among the NYS DEC, the City of Ithaca, Tompkins County, and local and national hydrilla experts to establish the best procedure.  That discussion led to the decision to have the Tompkins County Soil and Water Conservation District be the organization to request the formal permit.  Once that decision was made, the formal notification of landowners/leaseholders and the full 21-day opportunity for responses (or earlier, if all landowners  respond prior to the end of 21 days) needed to happen before the herbicide could be applied.

  5. Who's paying for this?  The NYS DEC will reimburse Tompkins County for about $50,000 of the cost of this application of the herbicide.  The Tompkins County Legislature has allocated about $26,000 from its reserves toward the cost.  The chemical company that provides endothall has kindly offered to contribute $15,000 towards the treatment.  All those funds should cover the direct costs.  City of Ithaca, Tompkins County Soil & Water Conservation District, Cooperative Extension, and many volunteers from multiple organizations have contributed substantial staff time to planning and executing the hydrilla management plan.  The County and the City will collaboratively make a request that NYS cover these costs as this is a State controlled water body.

  6. How will the Inlet closing work?  Buoys are being placed at the mouth of the Inlet during the first week of October.  The Tompkins County sheriff will patrol the inlet.  The U.S. Coast Guard is issuing a notice to marines that the Inlet is closed.  No boat traffic at all will be allowed.

    • The closing will extend from the Route 79 bridge (Buffalo Street Bridge) north to the mouth of the Inlet (see MAP).The Inlet is expected to be kept closed for 14 days, or as needed, to ensure that the herbicide has sufficient time to affect the exposed hydrilla. 
    • Sections of the Inlet south of the Rt. 79 bridge may remain closed after the herbicide treatment.  Infestations of hydrilla were discovered after the DEC permit application was submitted.  These areas may be able to be contained through hand removal or benthic barriers due to the location and smaller size.

  7. What will happen next? Once the initial control of hydrilla happens with the herbicide application, the Cayuga Inlet Hydrilla Task Force will use the winter to conduct a careful analysis of possible actions.  These might include applications of the same or different herbicides in 2012, physical suctioning up of hydrilla roots, or other actions.  The Inlet will most likely be closed again for short periods of time in 2012 for further treatment.

VI. HOW CAN i LEARN MORE?

Last Updated: April 23, 2012