Despite its relatively tranquil appearance from Cornell’s hilltop vantage point, Cayuga Lake is a warzone.
About two months ago, on Aug. 4, an intern at Cayuga Lake Floating Classroom, Jordan Stark, was taking a water sample when she spotted a leaf that didn’t look quite right. That leaf turned out to belong to an invasive species of aquatic plant originally from East Asia known as Hydrilla verticillata, but also known as water thyme.This is the first time the species has been spotted in upstate New York. “If she hadn’t seen it, we probably would not have known anything about it till next fall,” said Manager of Cornell Ponds and Research Support Specialist Robert Johnson, the scientist who identified the unknown plant as Hydrilla the morning after Stark’s initial discovery.As a result, the invasive plant has been growing unnoticed in thick vegetative mats for some time. It has since been rooting itself in the lake-bed in storage units known as tubers that will help it survive the winter and from which it is expected to regrow in spring.To remove as much of the biomass as quickly as possible before October 15th, the date around which the Hydrilla was anticipated to reproduce, the herbicide Endothall was applied last week. Johnson described it as “the most acceptable [herbicide] for our situation.” Endothall chosen for instead of Fluridone, the herbicide typically used to combat Hydrilla, which works gradually and requires about 60 days to take effect, Menninger explained ,because “by the time we got the permit, [Fluridone] would have been biologically irrelevant.” “Mechanical harvesting of Hydrilla would have been a disaster,” said Johnson, noting Hydrilla’s ability to propagate from smaller cut-up pieces of itself.Other methods, such as the introduction of a biocontrol, or a predatory species like grass carp, were also not chosen. Grass carp is sometimes used to keep Hydrilla in check elsewhere in the U.S., but only in isolated bodies of water. Since this fish is itself an invasive species, it could, like the Hydrilla, run the risk of spreading from Cayuga Lake to the rest of the Finger Lakes, and it go from there to the Great Lakes and even up the St. Lawrence River into Canada, thus making it a non-viable option.Cayuga Lake has seen invasive species before. For instance, Johnson likened the current predicament to the explosive growth of Eurasian Water Milfoil, another invasive species, after Tropical Storm Agnes in the 1970s. Eurasian Water Milfoil soon after became the dominant vegetation in Lake Cayuga, and, as he explained, devastated many businesses on the Lake. That invasive species has since been kept in check by the appearance of a certain species of moth that preys on it.Menninger and her colleagues will continue to monitor the effect of the herbicide over the next several weeks. Next year, more permanent measures will need to be undertaken to fully eradicate Hydrilla. Importantly, the storage tubers will need to be removed from the lake-bed to prevent its recurrence. “We really have to stay on top of this,” Johnson said.
Menninger and her colleagues will continue to monitor the effect of the herbicide over the next several weeks. Next year, more permanent measures will need to be undertaken to fully eradicate Hydrilla. Importantly, the storage tubers will need to be removed from the lake-bed to prevent its recurrence. “We really have to stay on top of this,” Johnson said.
Original Author: Bob Hackett