1. SONAR TREATMENT PROJECT

Herbicide applications were completed on Saratoga Lake to evaluate the potential for use of SONAR (fluridone) to control Eurasian Watermilfoil (EWM). During recent years, SONAR has been frequently used to control EWM in many locations in New York State.

The original proposed plan was to use the pellet formation (SRP) which had been used most frequently in NYS for partial lake treatment. The treatments were carried out on May 10, 2000 and June 1, 2000. This time period corresponds to the period of time when EWM is actively growing and many native species are less active. Selection of this time period for treatment has, in most cases, lead to the control of EWM with high survival of the native species. Preservation of native species may assist in long-term re-establishment of the native species in a natural balance in the lake.

Between May 10^th to June 9^th, record rainfalls occurred resulting in large volumes of water moving through the lake system. The aggregate total water level fluctuation reported from May 10^th through the end of June totaled approximately 4.7 feet. The National Weather Service office in Albany reported that through July the rainfall totals for the year were 9.67 inches above normal.

The size and location of the two 100-acre treatment blocks may also have contributed to lack of EWM control by the use of the SRP formulation. It was not feasible to treat a single location since insufficient data would be collected due to the fact that one location would not be representative of the lake shoreline condition. As an experimental testing of SONAR, it was impractical to treat larger areas at a higher cost.

The SONAR AS treatments did prove to be effective later in the summer. We believe that one reason that these partial-lake SONAR AS treatments were effective is due to the abundant weed growth both within and adjacent to the treatment plots and the fact that subsurface applications were carried out with weighted hoses trailing behind the Airboat. In addition, the high plant biomass restricted water exchange and helped keep this highly soluble liquid formulation of fluridone in contact with the targeted plants. The lack of water movement was clearly shown by the fact that milfoil located just outside the treatment plots showed few, if any, signs of fluridone uptake. Applying the additional 25 ppb of SONAR AS in lower concentrations over four consecutive weeks also helped to insure that the necessary contact time was achieved.

Even though SONAR AS did eventually control the milfoil, it took more than six weeks from the date of the first SONAR AS application. It is doubtful that liquid formulations of fluridone could be used for cost-effective partial-lake treatments in the spring, since there would be insufficient plant biomass to restrict water movement in and out of the treatment areas.

SUMMARY

• SONAR was effective in controlling EWM but control took a prolonged period of time.

• There were problems in sustaining SONAR concentration in the control plots most likely due to dilution by excessive rainfall.

• Larger treatment areas may correct the dilution issues that could include whole lake treatment.

• Use of SONAR AS liquid formulation in July or later may be a means of controlling EWM.

• During the Summer of 2001, the re-growth of EWM in the test plot should be carefully monitored.

• Pending results of the 2001 sampling if future treatment programs are considered larger more extensive areas should be completed.

• Consideration of a July treatment with SONAR AS should be evaluated. It should then be determined whether fluridone is still selective with later season mates.

Overview of 2000-2001 Research Projects

Two very important scientific research projects were initiated last year. Both projects were designed and conducted by the lake management firm, Adirondack Ecologists of Crown Point, NY.

2. Water Quality Monitoring Project:

Study Design

Epilimnetic (surface water) and hypolimnetic (deep water) samples were collected at both the north and south basins of Saratoga Lake in June and August. In addition, water samples were taken at the mouth of the Kayadeross Creek from a site in the lake’s outlet (Fish Creek). All samples were analyzed for total and ortho phosphorus, total nitrogen, nitrate, chloride, conductivity, total dissolved solids, and turbidity. Basin samples were additionally analyzed for pH, alkalinity ammonia, silica, sodium, magnesium, calcium, potassium, and iron. Surface water chlorophyll a levels were also measured. Please refer to the attached "List of Water Quality Parameters Analyzed" for a description of some of the analyte. A dissolved oxygen and temperature profile was performed at both lake basin testing stations in June and August, and secchi disk transparency data were also obtained.

Study Rationale

The primary objective of the monitoring project was to obtain current limnological data, which could be compared with historical data. By comparing this information, we may be able to determine whether any trends in the water quality of Saratoga Lake are noticeable. Secondary objectives of the water quality testing were to: (1) assess whether new management activities initiated in 2000 (i.e., SONAR treatment) would have a significant impact on the water quality of Saratoga Lake; and (2) to obtain anecdotal background data that could supplement information derived from the herbivore experimental release project.

Study Results – 1^st. year;

The scope of the water quality monitoring project was limited due to limited funding. However, enough limnological information was obtained to maintain the database already established and to provide valuable comparison data. For example, a seasonal comparison of north basin historical total phosphorus (TP), secchi disk transparency (SDT), and chlorophyll a (Chl a) data obtained via the CSLAP (Citizen’s Statewide Lake Assessment Program) from 1993-1997 and data collected by Adirondack Ecologists this past summer is as follows:

According to these data, both the June and August 2000 samples possessed lower TP and chlorophyll a levels than were measured, on average, from 1993 to 1997. In addition, SDT levels observed in June and August of this year were higher than the 5-year (1993-97) calculated mean. Since only one epilimnetic sample in June and one epilimnetic sample in August were taken in 2000 at the north basin testing site, caution must be employed when comparing these data with the CSLAP dataset - which possesses significantly more data points. Additional data collected in 2001 will assist in better understanding long-term water quality trends in Saratoga Lake surface water, but more testing could and should be performed.

The results of the dissolved oxygen/temperature profiles performed at the north and south lake basin testing sites on June 21 indicated that the respective water columns of both basins were well-oxygenated down almost entirely to the lake bottom. The August 28 profile indicated that Saratoga Lake was stratified, with the thermocline starting between 11 and 12 meters. The hypolimnetic waters of both basins were anaerobic, with profound oxygen depletion present in the north basin beneath 8 meters depth.

3. Herbivore (Experimental Release) Project:

Two trips to Saratoga Lake were made in the spring (April and June) of 2000 to perform reconnaissance inspections. An inspection of Manning Cove, an embayment situated on the western side of the lake that was originally viewed as a good potential site, yielded little hope as a site due to the absence of adequate milfoil stem densities. Heavily milfoil-infested areas located at the northern and southern ends of the lake were also deemed as being inappropriate sites due to their close proximity to planned SONAR applications. The only other site discovered that offered the qualities sought by the research team - high densities of milfoil situated just offshore of undeveloped land that possessed a satisfactory cover of leaf litter - was just north of Snake Hill.

What are weevils and what do they do?

The milfoil weevil (Euhrychiopsis lecontei) is a native North American beetle that has received a lot of attention by researchers lately as a potential biological control agent for Eurasian water milfoil (Myriophyllum spicatum). Euhrychiopsis can usually be seen in the water from late May to September. The adults live for about one or two months. During any given year, a weevil population may produce up to three generations during the course of the summer. Females lay eggs (2 per day on average) on the tips of apical meristems and these eggs can be as big as one-fifth of the size of the adult. These eggs can hatch in about three days, and after about two weeks, the larvae burrow into the stems of the host milfoil plant. Over the course of about 11 days, the larvae pupate into adults. (Note: Water temperature can dramatically influence development from egg to adult, e.g., 23 to 26 days at 25⁰ C vs. 38 to 41 days at 19⁰ C). In the fall, the adults either "raft" (on milfoil leaves or other floating debris) or swim into shore and overwinter just under the leaf litter near shore. Adults on shore are normally found within the first or second meter of the shoreline.

Adults feed primarily on the leaves located near the apical meristem of the plant. Larvae feed on lateral shoots after hatching, then they burrow into the stem of the plant. This activity is the most destructive to the milfoil plant. A loss of stem buoyancy may occur; causing the plant to drop out of the upper region of the photic or light-intensive zone (this is sometimes referred to as a "crash" by lake managers). In addition, damage caused by larval "mining" may introduce bacteria and other disease-causing vectors into the vascular system of the plant, potentially weakening or even killing it.

Study Design

In order to assess the effects of stocked weevils on milfoil plants in the research plots, the research team obtained pre-stocking and post-stocking data relative to the species of plants present within the research plots and their relative abundance. In addition, aquatic plant biomass (dry weight) data was obtained in June (pre- stocking) and August (two months post-stocking), along with an estimate of milfoil stem density. Surveys for weevils and other herbivorous insects (e.g., aquatic moth, milfoil midge, etc.) were also performed before and after stocking.

Study Rationale

The research site selected was divided into two equal-sized "zones", each measuring approximately 150 m². These zones, which were located roughly 50 meters offshore, were oriented east-west and measured 15 meters long and 10 meters wide. The water depth of the western zone, Zone A, was roughly 10 to 11 feet, whereas the depth of the eastern zone, Zone B, was roughly 8 feet. Zone B had a higher average milfoil stem density (24 stems per .1 m²) than did Zone A (17 stems per .1 m²).

Each zone was further divided into three 50 m² "plots". Two adjacently located plots in each zone were buoyed and one plot was unbuoyed. Each plot received the same level of research attention, as described above, throughout the entire lifespan of the project.

Adult weevils were stocked into one of the plots in Zone B at a rate of roughly 2 weevils per stem (23,950 weevils per 12,000 milfoil stems). Two separate stockings were planned within two weeks of each other to purposely avoid "putting all of our weevils in one basket."

The primary objective of the experimental project was to determine and document whether the weevils would damage and perhaps even control the milfoil within the stocked, and possibly adjacent, plots. A secondary objective was to determine and document the behavior (e.g., migration direction, reproductive success, etc.) of the weevils once stocked.

The research sites were delineated by marker buoys to alert users of the lake as to the presence of the weevils. On each buoy, a cautionary sticker was placed requesting that people not disturb the research site.

Study Schedule;

June 23 - Pre-stocking data collection (stem density, species composition, biomass, and herbivore community information)

June 29 - 10,000 weevils stocked and temporary marker buoys installed

July 12 - 13,950 weevils stocked

July 22 - herbivore survey

August 11 - herbivore survey

August 31 - herbivore survey and biomass data collection

October 10 - temporary marker buoys picked up

Study Results – 1^st. year

Intensive angler activity within and around the study plots (particularly those in Zone A) posed a significant challenge to researchers. In addition, mechanical harvesting activities in areas immediately contiguous to the stocked area (in Zone B) likely removed a significant amount of weevils as they migrated out of the stocked area. Despite these disruptive influences, some interesting and valuable data was collected during the first year of the project.

Species of aquatic plants observed within the research site included: Eurasian water milfoil, curly-leaf pondweed, coontail, water stargrass, eel grass or duck celery, flat-stem pondweed, and common waterweed or elodea. Eurasian watermilfoil was clearly the dominant species present in Zone B. Milfoil was not as abundant in Zone A, and in some biomass samples collected, curly-leaf pondweed was the dominant species.

During the field reconnaissance inspection, nesting bluegills were spotted in the immediate vicinity of the research site, and a small group of black ducks consistently used this area for feeding. The research team feared potential predation by these fish and ducks on stocked weevils, but realized that this type of predation would occur naturally in other locations around the lake and that predation was a variable that would affect the outcome of an experimental release in the lake regardless of the particular site chosen.

Stocked weevils appeared to do quite well early on in the project. Significant damage to apical meristems (tips of the plants) of milfoil from larval weevil "mining" was documented as early as July 12, and by July 22, we estimated that roughly 95%+ of the apical meristems in two of the Zone B plots were damaged. Unfortunately, this extensive damage did not precipitate a "crash" of the milfoil plants in this area, and the plants remained green right into October.

The research team was able to document the movement of the stocked weevils. They appeared to express an interest in migrating roughly southeast into shallower water and milfoil beds possessing thicker stem densities. This chosen course of migration unfortunately put them into areas that were harvested throughout the summer. We were also able to document the successful reproduction of stocked weevils; as empty pupae chambers were found on tip samples collected during post-stocking herbivore surveys.

It is also clear that weevils were already present in Saratoga Lake prior to our augmentation experiment. Very low densities of weevil larvae were discovered in our control plot on July 22 during a routine herbivore survey. Because of the large distance between the stocked area on the eastern side of the lake and the control plot on the western side of the lake, it is obvious that these weevils were not our stocked weevils. It is likely, however, that intensive mechanical harvesting efforts around the lake are artificially depressing the native population.

It will be interesting to observe what level of recruitment occurs this summer from stocked weevils. Additional data collected this summer should help us to better understand the fate of these weevils and of the experimental project.