Workers began herbicide applications this week in Cayuga Inlet to combat the spread of hydrilla, an invasive Asian plant that has grown in dense vegetative mats and driven the Ithaca mayor to declare a state of emergency. 

Allied Biological began applying an endothal herbicide to the inlet on Tuesday. Two air boats, which glide above the water, followed a GPS-guided path and applied the liquid herbicide through nozzles, according to Prof. Holly Menninger, natural resources, senior extension associate and coordinator of the New York Invasive Species Research Institute. No problems have been reported.  

The basic permit and application of the herbicide cost $95,000 so far, not including labor, according to Roxy Johnston, watershed coordinator for the City of Ithaca.

“We want to impress upon the state that this is bigger than just a local emergency,” Johnston said.  

Johnston said that though some residents expressed concern about the herbicide chemicals, the chemicals have been extensively tested and would pose no threat to animals or people.

Menninger said that “there is the potential for it to hit some native plants, but they are not all equally affected.”  

According to Menninger, the next steps are to monitor the water for endothal and observe the results of the treatment. Menninger said that the plants will start looking sickly within the next few weeks and will show some damage within the next few days if the treatment is successful.  

“We expect the hydrilla to disintegrate in place, but this will not happen for a few weeks,” Menninger said.  

Menninger said that the herbicide was applied before hydrilla produced turions, tiny vegetative buds that travel rapidly once they are released. The turions, estimated to begin growing on October 15, would exacerbate the problem andnecessitate reapplication of the treatment in the spring, according to Menninger. 

Allied Biological treated a 95-acre area, but an additional infestation was discovered near the Route 79 bridge after the city applied for an herbicide permit on September 14, Johnston said. As a result, this area went untreated. 

“By the time we found it, we had already started the 21-day countdown for property owners,” Johnston said. “The DEC said that we couldn’t change the treatment area size or map that delineates the treatment area. They said they would void the approval procedure, and we would have to start all over again.”

According to Johnston, the city, county and DEC are discussing treatment options for this area, but more surveys are necessary to understand the extent of the infestation.  

The inlet was closed to boat traffic last week to prepare for the application of the chemicals and to prevent the plant from spreading, Menninger said.

According to the Tompkins County Sheriff’s office, patrols to enforce the closure of the inlet will continue through Friday.

Menninger said the city wants to reopen the inlet on Saturday. She expects the city to reopen the 95-acre treatment area, but restrict access to the area by the Route 79 bridge.  

There was a one-day swimming restriction that has since been lifted, according to Menninger. However, water in the inlet will be prohibited for drinking for two weeks, the Ithaca Journal reported.

Wade Wykstra, commissioner of the Board of Public Works and chair of the Ownership Committee for the Ithaca Area Wastewater Treatment Plant, praised the efforts of the workers.

“It looks as though they went about it in an organized fashion,” Wykstra said. “I know that the project is in good hands.”  

Menninger said that extensive monitoring will continue next spring to determine where the hydrilla is located and direct corresponding treatment.