2009 Aquatic Technology End of Year Report

Aquatic Control Technology, Inc.

11 John Road ● Sutton, MA 01590-2509 ● (508) 865-1000 ● Fax (508) 865-1220 ● info@aquaticcontroltech.com

February 4, 2010

Lake Mishnock Preservation Association, Inc.

c/o Dan Albro, President

P.O. Box 240

Coventry, RI 02816

Re: 2009 Year‐End Report for Nuisance Aquatic Plant Management Program at Lake Mishnock

Dear Dan:

The invasive aquatic plant management program continued at Lake Mishnock for the fifth consecutive

season in 2009. The program continued to focus on control of invasive variable milfoil (Myriophylum heterophyllum) growth throughout the lake. Results of the 2009 program and ongoing management
recommendations are provided in the following report.
2009 TREATMENT PROGRAM SUMMARY
The major change effected during the 2009 season was the switch to Navigate herbicide (2,4‐D BEE

granular). Navigate was proven to be the most effective herbicide to control variable milfoil from New

Hampshire in a study completed by the U.S. Army Engineer Research and Development Center

(USAERDC) in 2007. 2,4‐D was not originally approved for use in Lake Mishnock due to the public wells

located downstream. Treatments with Reward herbicide (diquat) during the 2005 and 2006 season

were initially effective, but diquat is contact‐acting herbicide that only kills the foliage and stem tissue of

milfoil and significant regrowth was seen by the end of each summer. In 2007, pilot treatments with

Renovate OTF herbicide (triclopyr granular) were performed. Triclopyr is very similar to 2,4‐D and it did

effectively control variable milfoil (after the second, higher‐dose application), but it was determined notto be a cost

‐effective alternative for milfoil control at Lake Mishnock. Maintenance spot‐treatments

were performed in 2008 with diquat.

Navigate herbicide was permitted for use at Lake Mishnock in 2009, provided that a no‐treatment setback

was maintained around the Community Wellhead Protection Area.

Chronological Summary of 2009 Management Activities

• Prepared and submitted Pesticide Permit Application with RI DEM ............................................. February 23rd

• Received approved Permit from RI DEM ................................................................................................ May 6th

• Pre‐treatment inspection..................................................................................................................... May 11th

• Navigate herbicide spot treatment in Big and Little Mishnock............................................................. June 15th

• Post‐treatment inspection ...........................................................................................................September 3rd

• Final late season survey ................................................................................................................. October 26th

Following the pre‐treatment survey, we recommended proceeding with treatment of approximately 10 acres in 5 distinct areas to control milfoil growth. A treatment date of June 15th was selected. We

recommended delaying treatment until the first or second week of June to allow for more active milfoil

Lake Mishnock – Year‐End Report 2009 2 ACT, Inc.

Final 2009 Treatment Map; 10 acres total

Preliminary 2010 Treatment Map; 5‐6 acres total

growth to develop in order to

maximize herbicide uptake.

Navigate herbicide was applied at

100 pounds per acre, which is the

standard application rate used for

variable milfoil control. The

treatment was performed using

one of Aquatic Control’s Airboats

equipped with a calibrated

cyclone spreader. The treatment

proceeded smoothly and without

incident.

We conducted a post‐treatmentinspection on September 3rd. A

significant reduction of milfoil was

observed throughout the

treatment areas, but some small

patches of regrowth were seen in

the south‐central and southeast coves of Big Mishnock. Non‐target, native plants were scattered

throughout the lake at low to moderate densities. The dominant plants were submersed bladderwort

(Utricularia spp.) and ribbon‐leaf pondweed (Potamogeton epihydrus) and floating‐leaf white waterlily

(Nymphaea sp.) and watershield (Brasenia schreberi).A final late

‐season survey occurredon October 26th. By that time,

more noticeable milfoil regrowth

was seen in portions of Big and

Little Mishnock. The native plant

community still appeared to be

healthy.

The map depicted to the right

shows the GPS recordings (yellow

points) of milfoil plants seen

during the survey. Preliminary

treatment or management areas

were drawn around the most

abundant milfoil growth. The total

area requiring treatment appears

to be in the range of 5‐6 acres.

RECOMMENDATIONS AND EXPECTATIONS FOR 2010
Variable milfoil is a persistent invasive aquatic weed. The Navigate (2,4‐D) herbicide treatment

performed in 2009 achieved more effective milfoil control than the previous Reward (diquat) treatments

Lake Mishnock – Year‐End Report 2009 3 ACT, Inc.

and were considerably less expensive on a cost per acre treated basis than Renovate OTF (triclopyr)

herbicide. Still milfoil regrowth was seen in the areas that have historically harbored the most prolific

milfoil growth (south‐central and southeast cove of Big Mishnock and the south‐central portion of Little

Mishnock). Scattered regrowth was also seen in portions of the lake that were not treated in 2009.

We have been involved in several projects in New Hampshire in recent years that have been targeting

milfoil‐eradication, and we were contracted by the NH Department of Environmental Services to

conduct a field‐research project in 2009 that evaluated the efficacy and non‐target impacts of twodifferent application rates of 2,4

‐D. What we have learned from these projects is that re‐treatment is

necessary for effective milfoil control programs. Milfoil plants cannot absorb enough 2,4‐D herbicide tocompletely destroy their root structures. Even if a 90

‐95% reduction of milfoil biomass is achieved,regrowth will rapidly attempt to re‐colonize suitable areas. Usually areas with thick deposits of mucky

sediment are most prone to immediate milfoil regrowth. We have performed repeat treatments during

consecutive years at a couple of sites that have yielded significant reductions in milfoil. One lake was

treated for three consecutive years (2007, 2008 and 2009) and is not expecting that any treatment will

be required in 2010, but the lake association plans to continue with a vigilant diver hand‐pulling

program.

During the 2010 season, we recommend that LMPA continue with some area‐selective, spot‐treatmentusing Navigate (2,4‐D) herbicide. We would expect that 5‐6 acres (as depicted in the preliminary 2010

treatment map) may require treatment, but we would plan to finalize treatment areas with LMPA

following a pre‐treatment inspection. The estimated cost for spot‐treatment of 5‐6 acres inclusive offiling the DEM permit and performing pre and post

‐treatment surveys is approximately $3500. Should

additional areas require treatment, the per‐acre unit cost would be reduced accordingly. For example a10

‐acre treatment program would cost in the range of $5000. Treatment should continue to bescheduled for the early‐mid June period to maximize herbicide efficacy.

We also understand that there has been some concern raised over the growth of emergent plants and

waterlilies along developed shoreline swim and dock access areas. These plants can be effectively spottreated

with topical applications of Glyphosate herbicide, which was used at the lake in prior years. If

the plants are mature at the time of the milfoil treatment in early‐mid June, we would spot‐treat with

Glyphosate for no additional cost. Should a separate spot‐treatment with Glyphosate herbicide berequested or required later in the summer, the cost would range from $500

‐$1250 depending on the

size of the area being treated.

We trust that this report will assist LMPA in formulating management plans for the 2010 season. We do

believe that performing repeat treatments with Navigate (2,4‐D) herbicide in consecutive years is themost effective way to achieve longer‐lasting control of nuisance variable milfoil growth in Lake

Mishnock. As always, we value our relationship and look forward to working with you, Ken Brown and

the rest of the Lake Mishnock Preservation Association in 2010.

Sincerely,

AQUATIC CONTROL TECHNOLOGY, INC.

Marc Bellaud

Senior Biologist