Eurasian water-milfoil (Myriophyllum spicatum)

By: Melissa Negron

What we learned in class

An aquatic perennial weed Introduced in Chesapeake bay in the 1880’s is now

widespread throughout the U.S. Spreads primarily by plants fragments Economic Impacts

– Decrease in recreational activities Ex.) Fishing– Clog irrigation, carrals, gates– Decrease in hydroelectric generation by clogging intake pipes

Where did it come from?

- Native to Europe and Asia and Northern Africa.

- Accidentally introduced to the United States between the 1800’s &1940’s.

- 40 species of Myriophyllum in the world.- Presently found in 44 of the 50 states.

Where does it grow?

Found in aquatic habitats; reservoirs, rivers, natural lakes, freshwater and brackish estuaries.

Identification

Feather-like leaves found in whorls around the stem.

Mature leafs have 12 or more pairs of leaflets.

Native milfoil have less than 12

pairs of leaflets. If the water is clear root plants

grow 25-30 feet. If removed from water the

leaves collapse around the stem.

Reproduction

Able to reproduce rapidly and successfully through the form of plant fragments.

During late summer and fall the plant becomes brittle and breaks apart.

The distribution of these fragments float into new areas and establish as a new plant.

According to Couch and Nelson the first documentation of Eurasian water-milfoil was collected in October 1942 from a pond in Washington D.C.

Easily spread by fragmentation Water bodies of boats &

boating activities Commonly sold an aquarium

plant Accidentally Introduced

Colombia River

Introduction

Map (cont.)

First reported from Nevada, September 1995, from marinas along the northern shore of Lake Tahoe (Anderson and Ryan 1996). Uncommon in ditches and at lake margins in regions surrounding San Francisco Bay and San Joaquin Valley, California (Hickman 1993).

Problems

Upon invasion of new territories this plant reduces the species diversity.

Alters water body ecology Forms dense mats of

vegetation on surfaces of water which interfere with recreational activities.

Provides poor habitats for fish and other wildlife

Not on the U.S. Federal Noxious Weeds List– Widely Distributed & Difficult to control

Considered one of the worst weeds in the West

Category A Weed in Nevada– Limited in Distribution– Codes & Statutes will do whatever possible to

eradicate.

Management & Prevention

If invasion occurs almost impossible to remove.

Herbicides such as Sonar, 2,4-D & triclopyr-TEA are used in small bodies of water to manage infestation.

– Herbicides for aquatic weeds are questionable but triclopyr and 2,4-D appear to be effective.

Other Methods– Harvesting – Diver Dredging – Installation of Bottom Barriers– Rotovation – Sterile grass carp– Milfoil weevil

Limited situations

Identifying natives and invasive non-native.

Remove plant matter from boats.

Predicting Invasion Success of Eurasian Water milfoil

J. Aquat. Plant Manage 36: 28-32 (1998) John D. Madsen Goal: To correlate limnological parameters to Eurasian milfoil

dominance & from those relationships develop estimates predicting invasion success.

Tool in identifying & managing the spread of Eurasian water milfoil.

Predicting Invasion Success of Eurasian Water milfoil

300 lakes, 30 published, 14 unpublished Lakes in Vermont, New York, Michigan, Wisconsin,

Minnesota, Washington, Oregon, Alabama, Ontario, and British Columbia

1 year of data was collected for each lake Plant Communities; aquatic plant species presence

and/or abundance, Eurasian water milfoil biomass, Eurasian water milfoil percent cover, native plant percent cover, Eurasian water milfoil cover area littoral zone), native plant cover area (littoral zone).

Predicting Invasion Success of Eurasian Water milfoil

Results:– Lakes with more than 50%

Eurasian water milfoil dominance were found to have less than 60% cumulative native plant cover.

– Lakes with a Total Phosphorus of 20-60(μgL-1) or a Carlson’s Trophic State Index of 45-65 were most at risk of dominance by Eurasian water milfoil.

Results

Citations

Madsen JD (1998) Predicting Invasion Success of Eurasian Water milfoil J. Aquat. Plant Manage.36: 28-32

Mechanical Controls; (2003); Plant Management in Florida Waters; http://plants.ifas.ufl.edu/guide/mechcons.html; April 17, 2010.

Stevens County Cooperative Extension; (2001); Stevens County Noxious Weed Control Board http://www.co.stevens.wa.us/weedboard, April 13, 2010.

Washington State Department of Ecology; (2010); Non-native Invasive Freshwater Plants http://www.ecy.wa.gov/programs/wq/plants/weeds/milfoil.html April 13, 2010.

Question????????