Hydrilla Management Requires Flexible Solutions

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Tompkins Weekly 11-10-14

By James Balyszak

Similar to previous years, the 2014 hydrilla treatment season was an active and eventful one. Overall, 2014 herbicide treatments to thwart the growth of the invasive hydrilla (Hydrilla verticillata) plant were highly successful. Hydrilla tubers, the seeds that allow this invasive water weed to overwinter, are nearly gone from Cayuga Inlet. Hydrilla has been knocked back in Fall Creek, particularly in the Stewart Park Pond and golf course lagoon areas. Alternative management approaches were used in an area of Fall Creek where the herbicide was less effective and in some small, newly found patches in the southeast corner of the lake. Herbicides are only one tool in the arsenal to stop this aggressive pest from spreading into neighboring Finger Lakes, the Erie Canal, and beyond.

On September 23-24, trained members of the Hydrilla Task Force conducted a physical removal effort in the Fall Creek cove. Hydrilla patches were carefully removed by hand, and plant fragments created during the removal process were captured using nets. All removed materials were disposed of off-site. This removal effort was successful and resulted in a significant reduction of hydrilla biomass within the Fall Creek cove. Hydrilla tubers remaining in the sediment of the Fall Creek cove will give rise to hydrilla plants next season, so additional management strategies will be planned for the 2015 season.

Another development in 2014 was the discovery of additional hydrilla patches in the southeast corner of Cayuga Lake. These patches were adjacent to areas where divers successfully removed hydrilla by hand and installed benthic mats in August of 2013. The Task Force determined that benthic mat installation would again be a viable management option for these new patches. With assistance from the City of Ithaca and Town of Cazenovia (NY), benthic mats were acquired and installed over the hydrilla patches by a crew from Racine-Johnson Aquatic Ecologists. Installation was successful, and plant community monitoring will continue to track its efficacy.

It is important to note that physical removal and benthic barrier installation are not ideal management options for larger-scale hydrilla infestations. Based upon success observed in previous seasons, a combination herbicide treatment was again used to treat hydrilla in the Cayuga Inlet and Fall Creek. Initial herbicide treatment (trade name Aquathol-K) began on July 17 and July 29 in Fall Creek and the Cayuga Inlet, respectively. These treatments addressed hydrilla growing above the sediment. Follow-up herbicide treatment (trade name Sonar) was initiated on August 14 in Fall Creek and on August 26 in the Cayuga Inlet. Sonar treatments continued through October 8, when injection units in the Cayuga Inlet were turned off. These sustained Sonar treatments helped to address possible hydrilla regrowth.

The threat of hydrilla and other invasive species is a growing concern throughout New York State. Aquatic invaders threaten the freshwater resources that individuals and communities depend on for drinking water, recreation, business, and tourism. While some invasive species have yet to make their way into New York’s waters, some have already arrived. Once introduced, invasive species are capable of taking over the native ecosystem, causing untold environmental and economic damages.

The overarching goal of the Cayuga Lake Watershed Hydrilla Project is to eradicate local hydrilla infestations, and prevent their spread to Cayuga Lake and beyond. Great progress has been made using herbicide treatments since 2011. Alternative management strategies have provided additional means to address isolated hydrilla patches, without relying solely on traditional herbicide applications. Combining multiple management strategies will allow for adaptive and comprehensive management of hydrilla, leading to more effective control and eradication.

Ultimately, community awareness and support is critical to the success of preventing the spread of invasive species. To facilitate greater public awareness, the Hydrilla Task Force will be hosting a public update meeting on November 18, 2014 at 7:00 p.m. at the Tompkins County Public Library.

Hydrilla, Weeds and FishNovember 18, 2014, 7:00-8:30 p.m.

Tompkins County Public Library, Borg Warner

This FREE public program will cover 2014 hydrilla treatment efforts and progress, whether or not weed growth in the lake is changing, and other invasive species of concern. A reception to thank Hydrilla Hunter volunteers will precede the event starting at 6:30 p.m.




 James Balyszak is the Hydrilla Task Force program manager.





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