Bashan Lake, East Haddam - 2022
Bashan Lake is a 273-acre waterbody located in East Haddam, CT. It is one of Connecticut’s highest quality state-owned waterbodies and has extremely clear water. The lake is moderately developed with residential homes along the shoreline and public access through a state boat launch.
CAES IAPP has monitored and treated invasive plants in Bashan Lake for over 20 years. Previous aquatic plant surveys for all native and invasive plants were performed in 2004, 2014, 2016, and 2020. These surveys documented 13 – 26 plant species with the greatest number occurring in the latter years. Bashan Lake had extensive areas of invasive variable-leaf watermilfoil (Myriophyllum heterophyllum) and a small area of invasive fanwort (Cabomba caroliniana).
In 2014, the lake’s dam underwent a complete rebuild. In the process, the water was lowered approximately 18 feet. Rebuilding was completed in early 2015. When the lake was lowered, most of the variable-leaf watermilfoil that escaped CAES IAPP treatment was thought to have been killed by exposure to freezing and desiccation; however, in 2017, considerable areas of the plant reappeared. These areas were treated in the fall of 2017 with the herbicide Navigate. Unlike previous years where Navigate treatments were effective, the 2017 application offered little control. Resistance to Navigate was surmised. Fortunately, a new herbicide called ProcellaCOR became available, and CAES IAPP tested it in the fall of 2018. Successful variable-leaf watermilfoil control was obtained in all areas except for the boat launch cove. Better control was considered likely if an early summer treatment had been employed.
In June 2020, five acres of variable-leaf watermilfoil, mainly in the boat launch cove, were treated with ProcellaCOR. Our late summer 2020 survey found no variable-leaf watermilfoil anywhere in the lake. Because none was found, there is a likelihood that the herbicide moved into other parts of the lake. Fortunately, ProcellaCOR is selective to certain broadleaf plants and not harmful to most grassy plants. Among these are the common and state listed pondweeds (Potamogeton species). Our 2020 post-treatment plant survey showed 25 species inhabited the lake which is greater than any of our previous survey years. State listed Vasey’s pondweed (Potamogeton vaseyi) remained robust near transect 14. Fanwort was found in a small patch just north of the cove with the state boat launch by transect 3 and most was covered with a benthic barrier.
Our 2022 survey found an expansion of the fanwort, a few variable-leaf watermilfoil plants that were hand-pulled, and 25 native species. Vasey’s pondweed was not observed; however, we would expect a resurgence if the future. Charophyte was common at depths from 6-20 feet. A few very sparse patches of invasive phragmites (Phragmites australis) were also observed. The most common native species were purple bladderwort (Utricularia purpurea), common bladderwort (Utricularia macrorhiza), humped bladderwort (Utricularia gibba), arrowhead (Sagittaria species), snailseed pondweed (Potamogeton bicupulatus), waterwort (Elatine species), spikerush (Eleocharis species), coontail (Ceratophyllum demersum), and sevenangle pipewort (Eriocaulon aquaticum).
Addressing the expanding fanwort is a primary goal and the Bashan Lake Association is working with CAES to formulate a plan that prioritizes protection of state listed species and the native plant community.