Vigilance is Key in Eradicating Hydrilla

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Tompkins Weekly 6-15-15

By The Hydrilla Task Force of the Cayuga Lake Watershed

Hydrilla patches continue to burden the southeast corner of Cayuga Lake. Is all lost? We don’t think so.

Isolated patches in the southeast corner of Cayuga Lake pose the greatest threat for hydrilla spread. Considered one of the world’s worst aquatic invasive species, hydrilla (Hydrilla verticillata) is capable of spreading rapidly through plant fragmentation, vegetative buds, and subterranean tubers (seedbank). Viable stem and leaf fragments can be transported via boats, trailers, and recreational equipment. Hydrilla tubers can remain dormant in the sediment for years at a time, only to give rise to new populations in the future. Once established, hydrilla can outcompete beneficial native vegetation by creating thick vegetative mats that block sunlight and choke waterways. If nothing is done, hydrilla could take over the waters of New York State, leading to widespread ecological and economic impacts. As an example of the potential impacts, the state of Florida spends $20 to $30 million annually to control hydrilla in its waters. Given the number of freshwater bodies in New York, and the interconnectivity of these waters, the long-term management costs of a statewide hydrilla infestation in NY would certainly be on par with that of Florida.

A high school student found hydrilla in Cayuga Inlet in 2011. Since then, the Hydrilla Task Force of the Cayuga Lake Watershed (HTF) has been actively managing and eradicating populations of the highly invasive plant in the Cayuga Inlet to prevent its spread to Cayuga Lake, neighboring Finger Lakes, Erie Canal and beyond. The HTF is a partnership of municipal and agency staff, environmental groups, plant ecologists and concerned citizens.

In addition to herbicide treatments, plant ecologists and trained volunteers search the shallow waters of Cayuga Lake for any new patches. In 2013, hydrilla was discovered in the southeast corner of Cayuga Lake, adjacent to Stewart Park and the Ithaca Youth Bureau. Physical removal of hydrilla patches by hand and the installation of benthic barriers, a mat that rests on the lake bottom and smothers the plants, has been successful. However, these efforts have not fully eliminated the aggressive weed.

After consulting with national experts and peer reviewers, the HTF will try a more aggressive management approach in the southeast corner of the lake in 2015. The HTF will use herbicides in the open waters of Cayuga Lake for the first time. This will involve the application of Sonar H4C pellets (active ingredient fluridone) to a 30-acre treatment zone in the southeast corner of the lake in early to mid-July. The treatment will target hydrilla during its early growth stages along the lake bottom, when it is most vulnerable. As fluridone levels dilute and disperse following the initial application, routine “bump” applications of additional pellets will occur every 2-3 weeks. Bump treatments will continue through late September in order to maintain target herbicide concentrations, preventing further hydrilla growth and suppressing the establishment of tubers. The HTF aims to reduce and ultimately eradicate hydrilla in this section of Cayuga Lake. The success observed in the Cayuga Inlet since 2011 supports our optimism.

Since the beginning of herbicide treatments in the Cayuga Inlet, the Task Force has observed over a 95 percent decrease in the remaining hydrilla tuber seedbank population. Monitoring efforts are having difficulty finding any tubers in areas that previously had heavy hydrilla infestations. Simply put, hydrilla management and eradication efforts in the Cayuga Inlet have been incredibly successful!

Plant ecologists also found hydrilla in Fall Creek in 2013. The HTF responded with an herbicide treatment program similar to the one used in the Cayuga Inlet. Full eradication of all Cayuga Lake Watershed hydrilla populations is not expected until 2020. This timeframe is based on the need for multiple years of treatment to eliminate dormant hydrilla tubers.

Finding and stopping any additional hydrilla patches is crucial to truly winning the battle. The early detection of new isolated patches of hydrilla, and subsequent rapid management response activities while hydrilla populations are still low, means eradication is feasible. The Hydrilla Task Force does not believe it is a question of “have efforts failed?” Instead, the question is “will we allow previous successful efforts to fail by not taking the necessary steps to ensure that ALL hydrilla populations have been eradicated?” Early detection has given us the opportunity to proactively address isolated hydrilla patches in Cayuga Lake, before population levels increase and continue to spread. The opportunity for eradication still exists and continued treatment is necessary or New York could face statewide infestations and management costs similar to those observed in states like Florida.

Community awareness and support is critical to the success of these efforts. The Hydrilla Task Force invites the public to attend a FREE public update meeting on Thursday, June 25th from 6-8PM at the Ithaca Town Hall.

“Ecosystem Invaders: What’s In Your Watershed?”

June 25, 2015 6:00 – 8:00p.m.


This FREE public program will cover 2014 hydrilla treatment efforts and progress, as well as management plans for the upcoming 2015 treatment season.








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