From 2009 to 2016, CAES IAPP surveyed Fence Rock Lake in Guilford, CT to track the invasive plant Brazilian waterweed (Egeria densa). The plant was first detected in 2009 and continued to spread. In 2012, the western cove had several separate patches of Brazilian waterweed. In 2013, these patches coalesced across nearly the entire cove. The increase in the coverage found the plant growing in deeper water than all previous years. Brazilian waterweed was found on 60 percent of the transect points in 2013, compared to only 40 percent in 2012.

In 2014, the lake was treated with the herbicide Reward® using a bottom injection technique. In the summer of 2015 a small population of Brazilian waterweed remained so the lake was retreated. Our 2016 survey found no Brazilian waterweed and 13 native species: watershield (Brasenia schreberi), waterwort (Elatine species), spikerush (Eleocharis species), quillwort (Isoetes species), primrose-willow (Ludwigia species), low watermilfoil (Myriophyllum humile), slender naiad (Najas flexilis), yellow water lily (Nuphar variegata), white water lily (Nymphaea odorata), pickerelweed (Pontederia cordata), small pondweed (Potamogeton pusillus), cattail (Typha species), and humped bladderwort (Utricularia gibba). Slender naiad and small pondweed were the dominant species found.

In 2017, CAES IAPP performed another survey of Fence Rock Lake. For the second year in a row, no Brazilian waterweed was found. The 13 native species found in 2016 were found again as well as two additional native species: snailseed pondweed (Potamogeton bicupulatus) and arrowhead (Sagittaria species). Slender naiad and small pondweed were still the dominant species found, however the large patches found in 2016 were smaller in 2017. Waterwort, spikerush, primrose-willow, quillwort, low watermilfoil, and slender naiad were abundant along the majority of the shoreline. The southern shore was less populated than the rest of the shoreline. Overall, in 2017, the abundance of native species stayed roughly the same and the species richness increased.