As part of a comprehensive Watershed Management Plan, an innovative and experimental technology to control the growth and spread of Eurasian water milfoil (Myriophyllum spicatum) has been implemented on Saratoga Lake since June of 2000. CLICK HERE to view the first year study results.

A weevil species native to North America, Euhrychiopsis lecontei (commonly referred to as the milfoil weevil), has been introduced into Saratoga Lake on an experimental basis. For the past decade, researchers have been evaluating this organism as a potential biological control agent for the exotic plant Eurasian water milfoil (hereafter, referred to as EWM). The weevil, which is a small (adults are roughly 2mm in size) herbivorous insect of the beetle family Circulionidae, has been associated with significant declines in EWM populations in lakes, such as Brownington Pond in Orleans County, Vermont, Fish Lake in Dane County, Wisconsin, and McCollum Lake in McHenry County, Illinois.

Steven A. LaMere, a Certified Lake Manager and Certified Fisheries Professional, and owner of Adirondack Ecologists (AE), a lake management consulting firm located in Crown Point, New York, has been retained to design, implement, and oversee the research project. The primary objective of the bio-control project will be to determine the efficacy of the milfoil weevil in controlling EWM in Saratoga Lake. This will be accomplished by assessing the aquatic plant and herbivore communities of Saratoga Lake prior to and after stocking roughly 20,000 weevils into the lake.

A larva in chamber (before pupation - click to enlarge)

The research protocol calls for an investigation of the aquatic plants and herbivores currently present in Saratoga Lake in June of 2000. The investigation will take place in a number of permanent research sites selected and established by AE, and the weevils will be stocked shortly after the initial investigation is complete. Follow-up investigations in July and August of 2000 and June, July, and August of 2001 will hopefully allow AE the opportunity to evaluate the “initial” impact of the weevil stocking. It will likely take a minimum of five years, however, to assess the full impact of the project.

Based on some of the research that has been conducted around the country (e.g., Minnesota and Vermont), there is reason for optimism. We know a considerable amount about the lifecycle of the weevil and its herbivorous effects on EWM. Adult weevils spend the winter in the leaf litter and mud near the shoreline of a lake or pond. In May or June, they return to the lake to spend the summer in EWM “beds”. The female, which is capable of laying 30 to 100 tiny yellow eggs throughout her lifespan on the apical meristems (“growing tip”) of EWM plants, usually lives for about one month. After hatching (which normally takes about three days), the weevil larvae feed on the lateral shoots of EWM and then burrow into the stems of the plants.

It is this burrowing behavior that is particularly damaging to EWM plants. The larvae, in the process of entering into the stem, destroys the vascular tissue of the plant, thus exposing the plant to a potential loss of stem buoyancy. If and once this occurs, the EWM plant falls out of the water column where light may not be able to reach it, resulting in a loss of the plant’s ability to photosynthesize. In addition, it is theorized, that bacteria and other disease-causing vectors may become introduced into the EWM plant through the hole burrowed by the weevil, and this may also play a role in the plant’s demise.

Over the course of about 11 days, the larvae pupate into adults. The adult females mate and lay more eggs, and the cycle begins anew. In the late summer or early fall, the adults either fly into shore or “raft” in on EWM fragments. Natural (undeveloped) shoreline areas which possess a significant amount of leaf litter make good over-wintering habitat for the milfoil weevil. They normally are found buried underneath the leaf litter within 1 or 2 meters of the shoreline or in the shoreline mud.

The Saratoga Lake bio-control project is the first research project of its kind in New York. It promises to be a very high-profile undertaking, with a tremendous amount of interest expected on the behalf of state regulatory agency personnel, local and state government officials, academicians, and of course, Saratoga Lake residents and other riparian shoreowners from all over the northeastern U.S.

In order for the Saratoga Lake bio-control research project to be successful, AE is selecting research sites in areas where no other EWM management techniques will be employed during the lifespan of the program. Mechanical harvesting activity, which cuts the tops of the plants (apical meristems), removes the food source for the weevils and removes the weevils themselves, thus eliminating any chance of success that they might have of controlling the EWM. Chemical use (e.g., SONAR) would have much the same effect.

The research team is equally concerned about the effects of boating traffic within the confines of the established research sites, which will measure about 100 square meters each. To prevent boat propellers from destroying the growing tips of the EWM plants, and thus disrupting the weevils before they have a chance to exert control, AE has installed surface markers (buoys) around the research plots to delineate their position. Also, educational signs have been posted near launch sites to the lake, which describe the project and its scope.

With the cooperation and consideration of all stakeholders and users of the lake, this will prove to be a very interesting and valuable research effort.

[Photos reprinted with permission of Robert L. Johnson.]