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Eurasian Watermilfoil Myiophyllum spicatum

Jennifer Cunningham December 5, 2014 FSH 423

Figure 1: Left picture shows the size and whorl arrangement. Right picture is M. spicatum growing in Liberty Lake, WA. Photos from http://www.nwcb.wa.gov/detail.asp?weed=96 and http://libertylake.org/milfoil/

Classification that will stay upright when out of the water (WA. Dept. of Eco.). Order: Eurasian watermilfoil can grow in fresh water as Family: deep as 20-30 feet. It is a rhizomatous that forms dense mats that can become tangled Genus: underwater. Species: M. spicatum

Common Names: watermilfoil, spiked milfoil, milfoil

Identification Key

Eurasian watermilfoil is a perennial, submersed, . It has dissected that are feather like and arranged in whorls of four. This plant is sometimes confused with the Figure 3: Example of the whorl patter for Eurasian native Northern watermilfoil (Myriophyllum watermilfoil. Photo from Washington State sibericum), and they sometimes are Department of Ecology distinguished using DNA for a positive identification (WA State Dept. of Eco.). Flowering stems can be seen extending above the water’s surface. Tiny pink with either four or no petals grow in the axils of the

floral bracts which look like red spikes. The tips of the stems are tassel-like and often red. The stems branch out near the water’s surface and can easily fragment. Lower flowers are pistillate, and upper flowers are staminate.

Figure 2: Eurasian watermilfoil on the left,

Northern watermilfoil on the right. Photo from Washington State Department of Ecology

Eurasian watermilfoil has leaflets with closely spaced segments of more than twelve pairs. When pulled from the water, the leaflets tend to Figure 4: Examples of the stems of Eurasian watermilfoil collapse around the stem, unlike other milfoils above the water’s surface. Photo from www.nps.gov/plants/alient/pubs/midatlantic/mysp.htm

quickly enough to infest an entire lake within two years (WA State Dept. of Ecology).

In spring, as the temperature reaches 60°F (NOAA), its shoots will quickly grow and breach the water’s surface above a dense canopy. In mid to late July, the shoots will (Dept. of Ecology of WA.).

Feeding Habits

Eurasian Milfoil is a photosynthesizing plant that relies on a supply of sunlight, water, and carbon dioxide. Eurasian Milfoil requires a lot of sunlight so it forms dense mats at the surface of the water that can unfortunately shade out below it, and it can reduce the amount of oxygen in the water by preventing the wind

from mixing fresh oxygen into the water below Figure 5: An illustration of M. spicatum (Britton, the canopy (WA State Dept. of Ecology). 1913) Environmental Optima & Tolerances

M. spicatum prefers still or slow moving Life History and Basic Ecology water that is about 20 feet deep. It can be found Life Cycle & Reproduction in clusters downstream, in small bodies of water, or in coves because reproducing fragments are Eurasian watermilfoil is an aquatic plant carried there by wind and waves (King County with rapid reproduction abilities. While it can Gov., 2010). reproduce sexually, it rarely germinates the A large reason for Milfoil’s success as an hundreds of seeds it can produce. Instead, the invader is due to its adaptability. It can grow in plant will fragment itself in autumn, and those flowing water, in salinity up to 15 parts per fragments can then be carried away by the wind, thousand (1/2 the salinity of the Sound), and in waves, or human activities such as boating to depths up to 32 feet (WA State Dept. of reproduce elsewhere (Dept. of Ecology State of Ecology). WA. and NOAA). M. spicatum can tolerate a wide range of pH The annual growth pattern for Eurasian milfoil is (5.4-11), brackish water, and temperature ranges to fragment down to the crown in the fall, and (WA State Dept. of Ecology and King County then the plant will overwinter with stored Gov., 2010). M. spicatum prefers inorganic carbohydrates. This plant does not produce sediment, but it will grow on organic sediment turions (Benson et al. 2004). There are some also (WA State Dept. of Eco.). cases in which the milfoil will overwinter in an evergreen and maintain its biomass instead of Since it reproduces from fragments, it grows fragmenting to the crown. Milfoil can reproduce well in areas with disturbances like plant management, motor boating, and nutrient Eurasian watermilfoil is known to cross with loading (NOAA). native Northern watermilfoil, creating an invasive hybrid (King County Gov., 2010). M. spicatum is a submerged aquatic plant, but if its water source evaporates, it will develop a Current geographic distribution land form (Jefferson County Gov.). That land form can then return to its aquatic form when the Currently, M. spricatum has spread to water level rises. 44 of US States (Creed, 1998). In Washington State, it can be found in several lakes such as Biotic Associations (Pathogens, Parasites, Lake Washington, Lake Sammamish, Lake Commensalismes) Union, Green Lake, and Liberty Lake (King County Gov.2010). It can also be found from Dense growth of Eurasian milfoil Clallam and Jefferson counties on the western provides an ideal habitat for mosquito larvae most side of Washington to King County around because there are few other invertebrates to the Puget Sound up to Okanogan County by compete for space and few predatory fish to eat and down to Walla Walla County by the larvae (IN Dept. of Natural Resources). Oregon and the Columbia River (Nature Mapping Foundation).

Figure 6: Distribution in PNW (USGS)

Figure 6: US distribution of M. spicatum http://enviroscienceinc.com/eurasian -watermilfoil-aquatic-weeds/

Figure 7: M. spicatum distribution in WA State 1996

http://naturemappingfoundation.org/natmap/water1/4mysppic.html

History of invasiveness By 1998, M. spicatum had spread to 44 states M. spricatum is native to , , and three Canadian provinces (Creed, 1998). and North (Eiswerth et. al. 2000).

It was most likely introduced through Chesapeake Bay in the 1880’s, but its first Invasion Process recorded collection was in Washington D.C. in 1942 (Eiswerth et al. 2000). Pathways, Vectors, and Routes

M. spricatum had spread to 33 states by 1985, It is uncertain whether Eurasian and it was first found in Washington State in watermilfoil was first introduced through ballast 1965. The 1965 discovery in Lake Meridan, water or the aquarium trade, but several sources King County, did not generate concern. It site the aquarium trade as the most likely wasn’t until 1974 when M. spicatum was found pathway (University of Connecticut, 2009). It is flowing downriver from Canada’s Okanogan probable that the plant outgrew a tank which Lake into Washington’s Lake Osoyoos that was then dumped outside, and the plant’s management efforts were attempted (WA. Dept. fragments made it to the watershed where it of Eco.). established and spread (WA State Dept. of Eco.). Another pathway was shipping; Once M. spicatum was in Lake Osoyoos, it made Earthworm farmers in Oklahoma used the plant its way to the Columbia River. It was as packing material when they shipped out discovered in Western Washington in 1974 in boxes (WA State Dept. of Eco.) Lake Washington (WA State Dept. of Eco.). The most common current pathway is spread out, they don’t swim in it either (WA recreational boating (WA State Dept. of Eco.). State Dept of Eco. and Aiken et al. 1979). While there are warning signs and some boat cleaning stations, often boaters transport small Since M. spicatum grows earlier and faster than fragments of the plant as they travel between the native plants, it shades out the natives that water sources. grow under its canopy (Smith and Barko 1990). It is a leading cause in the displacement and While boats are the most common vector for M. reduction of diversity of native aquatic plants spicatum, anglers are also to blame for two (Madsen et al. 1991 and USGS). There are less reasons. Some small fragments cling to their macroinvertebrates present in the dense mats equipment, and there are cases in which anglers (Keast, 1984) which has far reaching impacts on have been caught intentionally introducing the the food cycle since the macros are a food plant into open water sources (WA State Dept. source for the native fish which are a food of Eco.). source for the native waterfowl.

An obvious route in Washington State is along While M. spicatum reduces the amount of the I-5 corridor (WA State Dept. of Eco.). This macroinvertebrates in the water (see figure 15), is most likely due to boaters traveling along the it does provide a perfect breeding habitat for highway between water sources. Another route mosquito larvae (IN Dept. of Natural is related to the history of migration of the plant Resources). from Canada. M. spicatum can be found along the Snake River, Okanogan River, and Columbia M. spicatum increases the phosphorous and River (Nature Mapping Foundation). nitrogen in the water, increases the pH, decreases the dissolved oxygen (DO), and Factors Influencing Establishment & Spread increases the temperature (WA state dept. of eco.). It affects the DO in two ways. Since M. Eurasian milfoil is a plant that can live spicatum has so much biomass, it affects the DO for several weeks outside of water, making it as it decomposes because the bacteria needed to possible for it to survive clinging to aquatic break it down causes eutrophication in the water. equipment that is transferred between bodies of The other way it decreases DO in the water is by water (IN Dept. of Natural Resources). Since it preventing wind circulation with the water grows best from fragments and is tolerant of a below its thick canopy at the water’s surface wide range of water temperatures and pHs, it can (EnviroScience, Inc.). Too little DO leads to quickly establish itself in a new area. Its high dead fish and a weak ecosystem. adaptability lends to easy establishment and spread.

Potential Ecological and Economical Impacts

M. spricatum has several negative impacts on the national, regional, and local scales. At the water source, M. spicatum provides a poor habitat for water fowl, fish, and wildlife. The local waterfowl and fish do not eat the plant, and since the plant is so dense and Figure8: A dead fish in a tangle of M. Spicatum (WA State Dept. of Eco.) M. spicatum poses a significant economical the amount of fish available in the water since it threat to Washington State. Every year, the state negatively impacts biodiversity. spends around $1 million to control this weed (Jefferson County Weed Control Board). Management Strategies & Control Uncontrolled, it clogs drains and dams causing Methods problems for power generation and irrigation (WA State Dept. of Eco.). Risk minimization and early detection are the best means of stopping the spread of M. On a recreational level, M. spicatum negatively spicatum to new bodies of water. This means impacts swimming, fishing, and boating (IN thoroughly rinsing and cleaning all aquatic Dept. of Natural Resources). The plants are equipment like boats, fishing rods, boots, and commonly stuck in boat props and difficult to trailers after exiting the water (Jeffereson detangle. County Weed Council).

Some methods of control promoted by many counties in Washington are covering the plant, hand pulling, raking, lowering the water level, rototilling, biological control, and

(Jefferson County Weed Council).

Covering the plant is useful with small quantities of M. spricatum. It involves blocking the sun with an opaque fabric to prevent photosynthesis (Jefferson County Weed Council).

Figure9: M. spricatum caught in a boat prop

(EviroScience, Inc)

Swimming can be impossible and dangerous in areas covered in M. spricatum. Between 1992 and 2003, there have been seven drowning incidents where people became tangled in the milfoil (Seattle Community Network). Several triathlon competitors became tangled in milfoil in the Columbia River in 2003 during a race Figure10: 2008 Oswego graduate student pulling (Seattle Community Network). This has an Eurasian milfoil from Skaneateles Lake. (syracuse economic component because cities must close parks and spend money to remove the plant for news) public safety. Hand pulling is similar to pulling weeds on land, Recreational fishing is affected by the presence but the plants must be disposed of away from the of milfoil because it can be impossible to fish water source since the plant propagates from through the canopy, and M. spricatum reduces fragments (Clallam County Weed Board). This method is only useful in small bodies of water but impractical in large bodies (King County spread further. Raking is ideal for maintaining Gov., 2010). open water in areas around docks (King County Gov., 2010). Lowering the water level can be done in the winter for several weeks which would expose Rototilling (rotovation) is a method that can help the M. spicatum to freezing temperatures. This the plant spread if not done correctly (Clallam method must be carefully considered because it County Weed Board). The British Columbia would affect the whole ecosystem (IN Dept. of Ministry of Environment has a barge with a Natural Resources). The other potential problem mounted rototilling machine that can churn is that M. spicatum can develop a land form for down 8 inches into the sediment. The Eurasian survival which can transition back to an aquatic milfoil floats to the surface where it is collected form once the water table rises (WA State Dept. and disposed of (WA State Dept. of Eco.). of Eco.). For the water drawback to be most Harvesting is a method similar to rototilling, it effective, the crown of the plant should be involves cutting the plant several feet below the exposed to the coldest temperatures (IL Dept. of water’s surface and collecting the plant parts that Natural Resources). The most effective float to the top (WA State Dept. of Eco.). drawbacks occur when the environment allows Harvesting is only a temporary fix for the for the milfoil to dry out, and this can be problem since the plant grows back. Cutting, difficult in Western Washington since it often harvesting, and tilling in King County requires a rains through the year (WA State Dept. of Eco.). permit since these mechanical procedures have the potential to spread the plant further.

Figure 11: A Lake Placid Shore Owner raking Milfoil http://www.adirondackdailyenterprise.com/page/content.d Figure 12: Harvesting Eurasian milfoil in etail/id/507278.html Washington (WA State Dept. of Ecology)

Raking involves a rake attached to a rope that is Three types of biological controls have been pulled through the water. This can help remove used for management: insects, Grass Carp, and plant density, but it does not pull up the root of plant pathogens (WA State Dept. of Eco.). the plant. In many lakes, this method is not The native milfoil (Euhrychiopsis allowed due to its negative impact on the lecontei) has had some success controlling Sockeye Salmon Spawning areas (Jefferson Eurasian milfoil, but it prefers the native County Weed Council). This method creates northern watermilfoil (). another potential problem in that it causes There are three challenges for using the fragmentation which can actually help the plant for control: large numbers of weevils are In the late 1960’s there was a mass dying of difficult to obtain, it takes years for them to have Eurasian milfoil in Lake Venice in Maryland an impact, and they can only minimize rather which sparked interest in using plant pathogens than eradicate the milfoil (King County Gov. 2010).

Figure 13: An adult milfoil weevil. Photo from EPA. http://water.epa.gov/type/lakes/images/bug.gif

The midge (Cricoptopus myriophylli) and as a form of biological control (WA State Dept. pyralid moth (Acetria ephemerella) are two of Eco.). No pathogen was isolated, but a other biological insect controls (IL Dept. of fungus (Mycoleptodiscus terrestris) has shown a Natural Resources). The pyralid moth, while it strong ability to reduce M. spricatum in a has a preference for Eurasian milfoil, is not laboratory setup (NOAA). generally used as a control because it is a 2, 4-D, Diquat, diquat with copper, endothall generalist feeder with the potential for collateral dipotassium salt, endothall with copper, and damage to the ecosystem (IL Dept. of Natural fluridone are used in Washington to Resources). This species also has low survival control M. spricatum (WA State Dept. of Eco.). rates. Herbicides have shown positive results in In 1963, the Grass Carp (Ctenopharyngodon reducing milfoil presence. idella) was introduced to control the M. Application is followed by diver surveillance spricatum (IL Dept. of Natural Resources). In and hand pulling. Herbicides with copper can multiple states, the carp has only eaten the M. only be used in irrigation ditches (WA State spicatum once the other sources of food have Dept. of Eco.). Herbicides application requires a been depleted, making carp a viable option only permit and must be applied by a licensed in bodies of water with M. spicatum pesticide applicator (Clallam County Weed monocultures (WA State Dept. of Eco.). Grass Board, 2000). Carp are not allowed in Lake Washington, Lake Sammamish or any body of water where the Endothall and diquat are temporary controls inlet or outlet can’t be screened to prevent the because they do not kill the roots (King County escape of fish (King County Gov., 2010). Gov., 2010). Application of herbicides can be beneficial when done to an area that has had the water level lowered or when the water has recently been dredged (King County Gov., 2010). Herbicide is best applied in spring before the plant is fully grown and in still water (NOAA).

Figure 14: Aquatic plant sampling took place at irregular time intervals at Kohlman Lake. Dates without bars

indicates an absence of Eurasian water milfoil from the sampling locations. (Ramsey-Washington Metro Watershed District 2012)

Expert Contact Information Current Research & Management Efforts Jenifer Parsons, WA State Dept. of Ecology's botanist, [email protected] A researcher at the University of Washington is conducting an evaluation of whether the milfoil King County Noxious Weed Control Program 206- weevil will be a suitable control for Eurasian 296-0290 watermilfoil in Washington. (WA State Dept. of

Eco.) Bellevue Manager [email protected]

Sammamish Manger [email protected] The US Army Corps of Engineers is continuing An “Aquatic Plants and Fish” pamphlet is research on plant pathogens for use on Eurasian published and distributed by the Washington milfoil (WA State Dept. of Eco.). State Department of Fish and Wildlife to educate the public (King County Gov., 2010). There are Current management in Washington State is also signs posted by infested water bodies to multifaceted and depends on the area in need of inform the public about the plant and what to work. Multiple approaches discussed earlier are do. considered and selected (King County Gov., 2010). Of those methods, the most common is a Bellevue closed the swimming areas at combination of herbicides and mechanical Meydenbauer, Clyde, and Newcastle Beach Park removal (MN Dept. of Natural Resources). in July 2014 to apply herbicide to reduce the Eurasian milfoil presence (Seattle Times News).

Figure 15: Rarefaction curves for invertebrate taxa on native and exotic milfoils in Saranac Lake (Wilson and Ricciardi, 2009)

Figure 16: Samples from various lakes in 2005 (Wilson and Ricciardi, 2009)

Literature Cited

Benson, A. J., C.C. Jacono, P.L. Fuller, Creed, R. P. 1998. A biogeographic E. R. McKercher., and M. M. Richerson. 2004. perspective on Eurasian watermilfoil declines: Summary Report of Nonindigenous Aquatic additional evidence for the role of herbivorous Species in U.S. Fish and Wildlife Service weevils in promoting declines. Journal of Region 5. U.S. Fish and Wildlife Service, Aquatic Plant Management 36: 16-22. Arlington, Va. 145 pp. University of Connecticut. 2009. Eiswerth, M.E., S.G. Donaldson, and Invasive Plant Atlas of New England. Eurasian W.S. Johnson. 2000.Potential environmental watermilfoil. impacts and economic damages of Eurasian Madsen, J.D., J.W. Sutherland, J.A. watermilfoil () in Bloomfield, L.W. Eichler, and C.W. Boylen. western Nevada and northeastern California. 1991. The decline of native vegetation under Weed Technology 14(3):511-518. dense Eurasian watermilfoil canopies. J. Aquatic Britton, N.L., and A. Brown. 1913. An Plant Management 29:94-99. illustrated flora of the northern United States, Aiken, S.G., P.R. Newroth and I. Wile. Canada and the British Possessions. 3 1979. The biology of Canadian weeds. vols. Charles Scribner's Sons, New York. Vol. 2: 34. Myriophyllum spicatum L. Canadian Journal 614. Courtesy of Kentucky Native Plant Society. of Plant Science 59:201-215. Scanned by Omnitek Inc.

Keast, A. 1984. The introduced aquatic Indiana Department of Natural Resources macrophyte Myriophyllum spicatum as habitat http://www.in.gov/dnr/files/EURASIAN_WAT for fish and their invertebrate prey. Canadian ERMILFOIL.pdf Journal of Zoology 62: 1289-1303. Bugwood Wiki Smith CG, Barko JW. 1990. Ecology of http://wiki.bugwood.org/Archive:BCIPEUS/Eur Eurasian watermilfoil). Journal of Aquatic Plant asian_Watermilfoil#History_of_Biological_Con Management 28:55-64 trol_Efforts_in_the_Eastern_United_States

Wilson, Sara J. and Anthony Ricciardi. NOAA 2009. Epiphytic macroinvertebrate communities http://nas.er.usgs.gov/queries/greatlakes/FactShe on Eurasian watermilfoil (Myriophyllum et.aspx?SpeciesID=237 spicatum) and native milfoils Myriophyllum sibericum and Myriophyllum alterniflorum in Seattle Community Network eastern . Canadian Journal of http://www.scn.org/earth/savelake/You.htm Fisheries and Aquatic Sciences 66: 21-24. Nature Mapping Foundation Key Sources of information http://naturemappingfoundation.org/natmap/wat er1/4spfrnox.html#eurmildist Department of Ecology for State of Washington http://www.ecy.wa.gov/programs/wq/plants/wee EnviroScience, Inc ds/aqua004.html http://enviroscienceinc.com/eurasian- watermilfoil-aquatic-weeds/ USDA National Agricultural Library http://www.invasivespeciesinfo.gov/aquatics/wa Minnesota Dept. Of Natural Resource termilfoil.shtml#cit http://www.dnr.state.mn.us/invasives/aquaticpla nts/milfoil/program.html King County Noxious Weed Control Program http://your.kingcounty.gov/dnrp/library/water- The Adirondack Almanack and- http://www.adirondackalmanack.com/2012/06/ land/weeds/BMPs/Milfoil_Myriophyllum_contr meet-the-invasive-milfoils.html ol.pdf Ramsey-Washington Metro Watershed Liberty Lake Sewer & Water District 1 http://www.rwmwd.org/index.asp?Type=B_BA http://libertylake.org/milfoil/ SIC&SEC=%7B845198F3-D798-42DF-92BD- 7F0683DFA82A%7D Jefferson County Noxious Weed Control Board http://www.co.jefferson.wa.us/WeedBoard/pdfs/ FactSheets/EurasianWatermilfoil.pdf

Clallam County Noxious Weed Council Board http://www.clallam.net/weed/documents/eurasia nwatermilfoil.pdf

Illinois Department of Natural Resources https://dnr.state.il.us/Stewardship/cd/biocontrol/ 6EurasianMilfoil.html