I've had many conversations on this subject with people who live around the lake. Some people dislike the aesthetics of the large patches, especially in the coves. Certainly, heavy concentrations can make boating or fishing difficult or impossible so some people would like to see the lilies brought under control if not eliminated. Others love the lilies just as they are or don't think they are a problem that warrants expenditure staff time or money right now.
According to the water quality consultants who monitor Reston's lakes and ponds, the lilies do not pose an ecological problem at this time. They provide good habitats for fish and can improve water quality. On the other hand, they are very aggressive and can push out other species or create stagnant areas with low oxygen levels. Therefore, at some uknown point in the future, depending on weather and other factors affecting their growth, they must be controlled.
The most effective control method is application of an herbicide called glyphosate, which is sprayed or swabbed directly on the leaves. It is considered very safe and has little or no effect on submerged plants. Harvesting is also an option, but is more expensive, less effective and less practical. Still some people may prefer it over herbicides for ecological reasons. (For more than you ever wanted to know about controlling water lilies see: http://pubs.ext.vt.edu/420/420-251/420-251.html or http://www.dec.ny.gov/docs/water_pdf/ch6apr05.pdf or http://www.ecy.wa.gov/programs/wq/plants/management/aqua028.html or http://www.ecy.wa.gov/programs/wq/plants/weeds/aqua005.html)
Full eradication (or close) with herbicide would cost around $5000 and will probably result in mats of decomposing lilies floating around the lake for a while. Some mitigation in key areas, such as around docks, could be done for less money, but would need to be repeated every few years.
Again, our consultant does not believe treatment is necessary this year and RA has not budgeted for it. If we are going to do something in 2012, however, September is the best time. Because this is still a judgement call, I feel community input is essential. Please use the form below to let me know your opinion or contact me with any questions.
Mike CollinsNorth Point RepresentativeReston Association Board of Directorsmike4ra@gmail.commobile: 571-969-4903
NOTE: This survey was not authorized by RA or the Board of Directors. Any opinions expressed above are mine.