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Posted 8/14/2014

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By Andrew Kornacki, Lynn Greer, Rich Ruby, Mike Netherland, Mike Greer
U.S. Army Corps of Engineers

The U.S. Army Corps of Engineers (USACE), Buffalo District, in cooperation with the U.S. Army Engineer Research and Development Center (ERDC), is serving as the lead agency for an eradication demonstration project for control of the invasive Hydrilla plant in the Erie Canal and Tonawanda Creek, Tonawanda, NY.

Hydrilla is an aggressive, opportunistic, aquatic nuisance plant species that has spread from its native Asia to every continent except Antarctica. It has been recognized as a serious aquatic invasive species threat in the United States for several decades. Eradication is particularly important for this project given the economic and ecological value of the waterway and risk of spread to multiple water bodies throughout New York and the Great Lakes.

Hydrilla’s thick mats can alter water chemistry and oxygen levels as well as foraging and spawning habitat for some fish species. Hydrilla can interfere with multiple recreational uses of a waterbody. It typically forms the densest patches in shallow high-visibility areas near recreational sites and along waterfront property.

“What makes hydrilla somewhat unique as a submersed invasive plant is the ability to cover large contiguous areas that can sometimes be measured in the thousands of acres,” said Mike Netherland, research biologist with ERDC.

It is unclear how hydrilla was introduced into the U.S. Some evidence points to the spread starting in Florida in the 1950s, when the plant was used to decorate aquariums. Aquariums were then dumped and the plant was released into the open waters. Hydrilla can now be found from coast-to-coast.

 “During this demonstration project we will be develop information on the concentration and exposure time requirements for Aquathol, a U.S. Environmental Protection Agency registered herbicide, on hydrilla, information that we can then apply to other control projects,” said Mike Greer, USACE project manager. “The objective for the first year is to reduce the hydrilla biomass by at least 95 percent and the number of tubers by at least 85 percent.”

Hydrilla propagates from fragments, turions (green, compact dormant buds), tubers (white or yellow, potato-like structures that form underground at the root), and rootcrowns (part of the root where the stem emerges), and has low light and carbon dioxide compensation points that allow it to grow very rapidly under warming conditions.

“Aquathol was applied July 22, 2014” Greer said. “The USACE/ERDC team worked with the New York State Canal Corporation to significantly reduce the flow of Erie Canal for 48 hours, while an application team spread about 1,850 gallons of Aquathol to seven miles of the westernmost portion of the canal via boat.”

Focused spraying of hydrilla is easy at first because the plant, once the tubers sprout, is visible from the surface of the water. In years after the first applications, plant density will be greatly reduced and that can lead to questions regarding the necessity of further applications. In the case of hydrilla, an eradication strategy requires continued diligence. One of the key benefits of the first year of application is the significant reduction in the threat of further spread from the canal.

“The monitoring, sampling and treatment will have to continue for several years at specific key times as the Army Corps of Engineers fights to keep hydrilla from spreading,” said Greer.  “The project’s greatest asset is the support it has from New York State Department of Environmental Conservation, U.S. Fish and Wildlife Service, New York Canal Corp., Western New York Hydrilla Task Force, as well as many local, state and federal officials.”

 “One thing essential in the control of invasive species, namely hydrilla, is education,” Netherland said. “Boaters need to know that they can transport this species to other water by not cleaning their trailer after pulling their boat out. The general public needs to understand that we cannot just pull this plant out. That could actually stimulate the spread of hydrilla.”