What is Eurasian Watermilfoil?
Eurasian watermilfoil is a non-native aquatic plant that is present in most U.S. states and much of Canada. This plant is known for its rapid growth and ability to spread, which can lead to significant problems within a lake. Milfoil forms dense beds that can seriously impair the recreational use of a lake, reduce the availability of fish spawning grounds, outcompete beneficial native plants, and otherwise alter a lake’s natural environment.
Eurasian watermilfoil originates from Europe, Asia and northern Africa. As an introduced aquatic plant species to this continent, Eurasian watermilfoil has no natural controls (insects, bacteria, fungi) to keep its growth in check. Milfoil stems can reach the surface in up to 20 feet of water, growing up from the lake bottom each year from a fibrous root system. Milfoil grows and spreads extremely quickly, forming dense surface mats. Eurasian watermilfoil will grow readily in many types of water bodies, as well as in almost any bottom type: silty, sandy, or rocky.
Eurasian watermilfoil reproduces almost exclusively by the breaking off of stem pieces which can drift away, sink, develop roots, and grow into new plants. A stem fragment just a few inches long can start a new plant. This fragmentation occurs both naturally and as a result of human activity. Within a lake, wind and waves may break plants loose, allowing them to drift into new locations and become established. Boating activity through dense milfoil beds also contributes to the fragmenting and spread of milfoil plants.
Removal and Control
Eurasian watermilfoil was introduced to Lake Fairlee over two decades ago, likely by fragments from a boat or trailer. The Lake Fairlee Association was established in part to organize activities to control milfoil and prevent the introduction of other invasive species to Lake Fairlee. There are several methods to remove milfoil, many of which have been used over the years on Lake Fairlee.
Hand-Pulling & Fragment Cleanup
Milfoil can be hand-pulled at any time during the season and does not require a permit as long as no mechanical methods are used. When hand-pulling, it is very important to be sure to remove the whole plant, including the roots, and to also remove any plant fragments that may occur during the removal. While fragments can occur any time, milfoil plants naturally become brittle in the fall and fragment more easily. If diving or snorkeling when hand-pulling, a mesh bag should be used to collect the milfoil to be able to bring it to the surface, remove it from the lake and reduce escaping fragments. It is also beneficial to remove floating milfoil fragments from the waterbody so they do not grow into new plants.
Diver-Assisted Suction Harvesting (DASH)
DASH crews hand-pull milfoil by the roots from the lakebed and place the plant into a suction tube. This tube pulls the plant up to the surface to a boat with a collection basin where a team member will load the milfoil into buckets for transport from the lake. In areas where milfoil is present among native plants, divers are selective and only remove the milfoil while leaving native plants alone. DASH require a permit from the Vermont DEC and typically can’t begin before July 1st to protect fish spawning. In 2020, the Lake Fairlee Association obtained the necessary permit and have been conducting DASH to augment other control measures.
Eurasian watermilfoil originates from Europe, Asia and northern Africa. As an introduced aquatic plant species to this continent, Eurasian watermilfoil has no natural controls (insects, bacteria, fungi) to keep its growth in check. Milfoil stems can reach the surface in up to 20 feet of water, growing up from the lake bottom each year from a fibrous root system. Milfoil grows and spreads extremely quickly, forming dense surface mats. Eurasian watermilfoil will grow readily in many types of water bodies, as well as in almost any bottom type: silty, sandy, or rocky.
Eurasian watermilfoil reproduces almost exclusively by the breaking off of stem pieces which can drift away, sink, develop roots, and grow into new plants. A stem fragment just a few inches long can start a new plant. This fragmentation occurs both naturally and as a result of human activity. Within a lake, wind and waves may break plants loose, allowing them to drift into new locations and become established. Boating activity through dense milfoil beds also contributes to the fragmenting and spread of milfoil plants.
Removal and Control
Eurasian watermilfoil was introduced to Lake Fairlee over two decades ago, likely by fragments from a boat or trailer. The Lake Fairlee Association was established in part to organize activities to control milfoil and prevent the introduction of other invasive species to Lake Fairlee. There are several methods to remove milfoil, many of which have been used over the years on Lake Fairlee.
Hand-Pulling & Fragment Cleanup
Milfoil can be hand-pulled at any time during the season and does not require a permit as long as no mechanical methods are used. When hand-pulling, it is very important to be sure to remove the whole plant, including the roots, and to also remove any plant fragments that may occur during the removal. While fragments can occur any time, milfoil plants naturally become brittle in the fall and fragment more easily. If diving or snorkeling when hand-pulling, a mesh bag should be used to collect the milfoil to be able to bring it to the surface, remove it from the lake and reduce escaping fragments. It is also beneficial to remove floating milfoil fragments from the waterbody so they do not grow into new plants.
Diver-Assisted Suction Harvesting (DASH)
DASH crews hand-pull milfoil by the roots from the lakebed and place the plant into a suction tube. This tube pulls the plant up to the surface to a boat with a collection basin where a team member will load the milfoil into buckets for transport from the lake. In areas where milfoil is present among native plants, divers are selective and only remove the milfoil while leaving native plants alone. DASH require a permit from the Vermont DEC and typically can’t begin before July 1st to protect fish spawning. In 2020, the Lake Fairlee Association obtained the necessary permit and have been conducting DASH to augment other control measures.
Benthic Barriers
Benthic barriers are mats (which can be made of various materials) that are weighted and placed on the lakebed to prevent sunlight from reaching covered plants. These bottom barriers can be effective but are not selective. All plants under the mat will die, and the mats can also have a negative impact on invertebrates and slow moving organisms like mussels. The use of benthic barriers requires a permit from the Vermont DEC, and they may be installed on July 1st and must be removed on October 1st. The Lake Fairlee Association used benthic barriers to control milfoil for several years. However, it is a labor intensive and costly solution and was eventually abandoned for other, more targeted solutions.
Herbicides
Aquatic herbicides are another tool that can be used to control milfoil. Over the past several years, the herbicide ProcellaCOR has been successful in controlling milfoil in lakes in Vermont and around the country as part of an integrated control plan. Vermont DEC has a rigorous process for applicants seeking to obtain an Aquatic Nuisance Control (ANC) permit to use an herbicide in waters of Vermont. In 2022, the Lake Fairlee Associaiton obtained a permit and used ProcellaCOR for the first time for milfoil control.
ProcellaCOR is highly selective to milfoil, but some native plants found in some Vermont lakes may be impacted by a treatment. A recent statistical analysis by the Vermont DEC of lakes treated with ProcellaCOR saw a statistically significant increase in frequency of occurrence of native plants, and a decrease in milfoil. The Lake Fairlee Association continues to work with the Vermont DEC and lake management professionals to plan the use of ProcellaCOR to continue to reduce the levels of milfoil in Lake Fairlee.
Watershed Management (Phosphorus Reduction)
Aquatic plant growth is fueled by phosphorus in the water, so working to mitigate sources of phosphorus entering a lake can help to limit excessive plant growth, and improve water quality. Phosphorus can be carried into the lake by runoff from stormwater events and malfunctioning septic systems.
The Lake Fairlee Association actively promotes Vermont DEC initiatives like Lake Wise, Stormwater Master Plans, Lake Watershed Action Plans, and Wastewater Workshops as ways to reduce phosphorus levels in Lake Fairlee.
Benthic barriers are mats (which can be made of various materials) that are weighted and placed on the lakebed to prevent sunlight from reaching covered plants. These bottom barriers can be effective but are not selective. All plants under the mat will die, and the mats can also have a negative impact on invertebrates and slow moving organisms like mussels. The use of benthic barriers requires a permit from the Vermont DEC, and they may be installed on July 1st and must be removed on October 1st. The Lake Fairlee Association used benthic barriers to control milfoil for several years. However, it is a labor intensive and costly solution and was eventually abandoned for other, more targeted solutions.
Herbicides
Aquatic herbicides are another tool that can be used to control milfoil. Over the past several years, the herbicide ProcellaCOR has been successful in controlling milfoil in lakes in Vermont and around the country as part of an integrated control plan. Vermont DEC has a rigorous process for applicants seeking to obtain an Aquatic Nuisance Control (ANC) permit to use an herbicide in waters of Vermont. In 2022, the Lake Fairlee Associaiton obtained a permit and used ProcellaCOR for the first time for milfoil control.
ProcellaCOR is highly selective to milfoil, but some native plants found in some Vermont lakes may be impacted by a treatment. A recent statistical analysis by the Vermont DEC of lakes treated with ProcellaCOR saw a statistically significant increase in frequency of occurrence of native plants, and a decrease in milfoil. The Lake Fairlee Association continues to work with the Vermont DEC and lake management professionals to plan the use of ProcellaCOR to continue to reduce the levels of milfoil in Lake Fairlee.
Watershed Management (Phosphorus Reduction)
Aquatic plant growth is fueled by phosphorus in the water, so working to mitigate sources of phosphorus entering a lake can help to limit excessive plant growth, and improve water quality. Phosphorus can be carried into the lake by runoff from stormwater events and malfunctioning septic systems.
The Lake Fairlee Association actively promotes Vermont DEC initiatives like Lake Wise, Stormwater Master Plans, Lake Watershed Action Plans, and Wastewater Workshops as ways to reduce phosphorus levels in Lake Fairlee.