FAQ’s To Solitude

Question by Sara to Solitude Lake Management:

What are your recommendations for Bungay weed management following your weed survey?

  • Dom and I sat together and game planned for Bungay Lake based on our vegetation maps. 
  • We do not feel as if hydro-raking is a great fit given the species assemblage.  Both fanwort and milfoil spread through fragmentation, meaning that a high powered piece of equipment like a hydro-rake is likely spreading these invasives.
  • Additionally, there is a large amount of acreage of both fanwort and milfoil, so the cost to manage these large areas with the hydro-rake would be tremendously expensive. 
  • For this reason, we recommend the use of an herbicide called Sonar (fluridone).  Sonar is effective on fanwort and milfoil and should bang up the tape grass as well as the lilies.  Sonar is a systemic herbicide that provides multi-year nuisance level control in the treated areas.  It works by building up a concentration of the herbicide and maintaining that concentration for a period of 30 days and potentially up to 90 days.  It is added through a series of multiple applications throughout the season, starting early in the growing season (usually May for fanwort). 
  • Dom and I priced out treating your priority areas, which is about 40 – acres of treatment and essentially includes all the marked areas on the map, except for the green area in the southern portion of the Lake.  A Sonar treatment program for these areas came out at $39,975 and includes pre- and post-treatment monitoring, the Sonar treatment program (including all product and labor), herbicide residue testing, as well as year-end-report. It would be possible to treat just some of the priority areas if the cost is high, but the actual cost per acre would go up, as we’d have to achieve a higher concentration. 
  • Additionally, we could likely include the lower half of the Lake (the green area on the map) for not too much more, with the way the concentrations work.  We figured the priority areas would be a good starting point.  Once we get the invasive managed, we could discuss hydro-raking to clean up individual shorelines for organic matter, leaves, etc. Hopefully this gives you something and some pricing to start with and we can work towards finalizing something soon.

Follow-up Questions by Sara to Solitude Lake Management:

Is this a one-year application?

  • The treatment itself would be over the course of the 2019 season.  The product, Sonar (fluridone), is a systemic herbicide that works by maintaining a concentration throughout the season.  We achieve this through multiple applications all conducted during the same season.

How long does it work for?

  • Typically you will expect two to three years of nuisance level control of the fanwort and two years of nuisance level control of the milfoil; unfortunately tapegrass is a wildcard, it will likely be banged up during the year of treatment but will bounce back in subsequent years, you could potentially see some benefit in the tape grass control in the year after the treatment.  Tapegrass is likely helping limit fanwort and milfoil growth in some of the areas on the eastern and western shorelines.

How much would it cost for all the areas on the map?

  • A whole pond Sonar application for would be $54,160.

How many years do you think we would need to continue the treatment?

  • The proposed Sonar treatment should be thought of as almost a “reset.”  It will achieve great control of the target invasive species, but eradication is impossible.  We recommend this “Sonar reset” to get the system under control and recommend an annual management program after the 2019 season to “maintain desirable conditions.” 
  • Following the Sonar treatment program, management of regrowth of the target invasive species (fanwort and milfoil) can be conducted at a significantly lower cost.  We recommend budgeting $12,500 per year to manage regrowth starting in 2020 and we should be able to stay at that cost for the next several years after the initial treatment in 2019. 
  • Tapegrass is a bit of a different issue and would be managed separately from that scope/cost.

Are there and other lakes in the area that you have treated with the herbicide before, References of other lakes?

Billington Sea


Plymouth, MA

Billington Sea Association


Contact: Mike Leary


Bartlett Pond


Northborough, MA

Town of Northborough


Contact: Kathy Joubert


Turkey Hill Pond


Rutland/Paxton, MA

Turkey Hill Pond Association


Contact: Judy Savage


  • Above are just three that I could think of off the top of my head from this past season.  Billington Sea and Bartlett are long time clients that conduct the Sonar program every 3-4 years or so and can attest to multi-year control.  Turkey Hill Pond was a new application for us in 2018 and was very successful.  All three were Sonar treatment programs for control of milfoil and fanwort.  If you need more, I can definitely send more along as we’ve conducted hundreds of Sonar treatment programs over the last several decades.

Are there any restrictions on swimming?

  • No, there are no label restrictions on recreational activities such as swimming, boating or fishing.  It is customary that we close down the waterbody during the day of treatment simply as our own company protocol, however this is not required by the product manufacturer and we can work with you on this.  The only restriction to note in regards to Sonar is an irrigation restriction (meaning if residents are actively drawing water out of Bungay Lake to water their lawn or gardens, this would be restricted while the product has an active concentration in the water).

Is it harmful to fish or pets?

  • Absolutely not.  Sonar is actually approved for use in drinking water.  This product is approved for aquatics use by the EPA, as well as the State of Massachusetts and has undergone a strict review.  It has been in use for decades.

Additionally we did decide to do a full draw down this year of 4 feet to try and freeze out some of the weeds along the shoreline. There is some question among the board on what weeds are affected by the freezing would you mind clarifying for us which weeds it works on in particular Milfoil, Tape grass, Fanwort and Cattail .

  • Drawdowns are definitely a roll of the dice as you will need several consecutive days of sub-zero temperatures without having the prior insulation of snow cover to insulate the plants.  Only one in every 5+ years of drawdowns is a successful drawn down year.  If the ideal conditions are observed you may see some impact to the milfoil and fanwort.  You may see some minimal impact to the tape grass and no effect on cattails.