Scientists, regulators, local and state officials, and other interested parties met at O’Hara’s Marina on Oct. 8 for a third consecutive end-of-season assessment of efforts to control the spread of invasive plants. Their focus was on hydrilla, and the news was encouraging.
Only three small beds were detected in the July aquatic plant survey, and none of the plants appeared to be healthy. These plants were found near the marina in an area of high boat traffic. It is important to keep this area clear of hydrilla to prevent fragmentation from passing boat propellers. Last year, extensive hydrilla beds were found along the eastern shoreline of the northeast cove, from O’Hara’s Landing to the state boat launch and into the area mixed with the waterlilies.
This progress was reported to members of the Twin Lakes Association at the annual meeting in August. Treatments with the herbicide Sonar were successful enough that the final two scheduled applications this year were scrapped.
The experts agreed that while the news was good, the problem is far from solved. Hydrilla fragments are notoriously resilient. They can embed in the lake bottom and bloom years later. The experts recommend that the TLA continue treatments next year and beyond.
We expect treatment costs will moderate in the coming years, but the heightened level of surveillance will continue. The TLA will spend about $400,000 on lake management in 2026. The organization is embarking on another fall fundraising campaign, asking members and other lake goers with the ability to donate at least $1,000.
Joining TLA board members at the meeting were vendors who monitor water quality, and supply and apply herbicides. Multiple representatives from the Connecticut Department of Energy and Environmental Protection, including rare-plant specialists from the Natural Diversity Data Base, the Army Corps of Engineers, a state official from Massachusetts, and representatives from four lake associations, also attended. Additionally, State Rep. Maria Horn and Salisbury Selectperson Kitty Kiefer were present.
Below: Dominic Meringolo, environmental engineer with Solitude Lake Management, addresses the TLA coalition. 
The recent success in controlling the spread of the Connecticut River strain of hydrilla at Twin Lakes is a bright spot in an otherwise dismal record of control across the northeast. TLA efforts are being closely watched by environmentalists, scientists, state and local officials, and many lake associations. The TLA is committed to sharing its experience broadly.
Limnologist George Knoecklein is conducting one more extensive aquatic plant survey in late October. This will include a diver to assess plant growth in deeper water. We expect some impact on native plants, including one endangered species found among the waterlilies at the north end. However, this plant is abundant in Middle Twin and may regrow naturally in East Twin in the coming seasons.
The experts recognize that finding a balance between eliminating hydrilla while minimizing the harm to native plants is an interactive process that will take time. They are in broad agreement that hydrilla must be stopped because, left unchecked, it can grow three inches a day and would outcompete native and rare plants. This, in turn, would alter water chemistry and harm fish and other wildlife.
All data is being shared with the authorities that issue permits for the TLA to apply herbicides. You may find more details on the meeting in the minutes posted on the TLA website.