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  •  Najas minor (Photo: E. Gilg and K. Schumann, Das Pflanzenreich. Hausschatz des Wissens,    http://www.biolib.de)
  • Brittle naiad (Photo: Robert H. Molenbrock, http://plants.usda.gov/java/profile?symbol=NAMI )
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Common name
slender-leaved naiad (English), brittle naiad (English), brittle waternymph (English), slender naiad (English), European naiad (English), minor naiad (English), spiny-leaf naiad (English)
Synonym
Caulinia minor , (All) Coss. & Germ.
Similar species
Najas flexilis, Ceratophyllum, Najas gracillima, Najas guadalupensis
Summary
Najas minor is a submerged aquatic herb native to Europe and Asia that has established in eastern United States and Ontario. Initially recorded in the 1930s, it has established populations in 26 states in the US. It creates dense, monospecific stands that may displace native aquatic plants and reduce the recreational and aesthetic value of lakes, ponds, and rivers.
Species Description
Najas minor is a submersed, annual, aquatic herb. Its growth is usually compact and relatively bushy. The stems may reach up to 2.5 m long and are profusely branched near their apex. Leaves are opposite or subopposite, about 1 mm wide and 0.5 to 3.5 cm long, becoming stiff and recurved with age. Leaves have 7 to 15 small, but conspicuous teeth along each side of the leaf. Sheaths at the base of the leaf are truncate to auriculate, with fine teeth along the upper margin. Flowers are small, inconspicuous, and borne in the leaf axils on the same plant. Fruits are single seeded but abundantly produced. Fruits are 1.5 to 3.0 mm long and slightly curved with rectangular areolae arranged in distinct longitudinal rows. (EL-ERDC, 2007; Cao, 2010).
Lifecycle Stages
The reproductive season of Najas minor starts in July, when flowers appear. Seed production peaks in September, and continues into October. During the late summer or early fall, the stems become brittle, and the profusely branched apical portions of the stem break into small fragments. Seeds remain attached in the leaf axils, and the fragments are dispersed by wind and water currents. Seed germination occurs in early spring to late summer (Cao, 2010; DNR, 2007).
Uses
Najas minor is a preferred food source for waterfowl who readily consume its abundant seed supply (DNR, 2007).
Habitat Description
Najas minor prefers calm waters such as ponds, lakes, and reservoirs but may grow in streams and rivers as well. It prefers alkaline environments and is known to inhabit pH levels of 6.0-9.3 with an optimum range of about 6.6-7.2. It occurs of depths of up to 5 m with an ideal optimum of about 0.5-2 m and temperatures down to 8°C. It may inhabit brackish waters with a salinity of up to 0.3 ppt. N. minor is tolerant to turbidity and eutrophic conditions, which may allow it to out compete and replace native species (DNR, 2007; Wentz & Stuckey, 1971; Robinson, 2004)
Reproduction
Najas minor reproduces sexually and asexually. Sexual production of an abundant seed supply and seed banks of up to tens of millions of seeds/ha appears to be its primary means of reproduction. It may also reproduce vegetatively producing clonal populations that may fragment and propogate (DNR, 2007; EL-EDRC, 2007)
Pathway
Najas minor may be introduced through disposal of aquarium species (DNR, 2007).Najas minor or its seeds may cling to boat hulls or boat trailers in inconspicuous places and be transported to other locations where they can establish (Capers et al, 2005).

Principal source: Department of Natural Resources (DNR), Wisconsin., 2007. Aquatic Plant Brittle/Lesser/Bushy/Slender/Spiny/Minor Naiad; Waternymph
Environmental Laboratory (EL) U.S. Army Engineer Research and Development Center (ERDC), 2007. Information Sheet: Najas minor L. (Spiny Naiad)
Ling Cao. 2010. Najas minor. USGS Nonindigenous Aquatic Species Database, Gainesville, FL.

Compiler: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)

Review: Robert S. Capers, plant collections manager, George Safford Torrey Herbarium, Department of Ecology and Evolutionary Biology, University of Connecticut

Publication date: 2013-01-04

Recommended citation: Global Invasive Species Database (2018) Species profile: Najas minor. Downloaded from http://www.iucngisd.org/gisd/species.php?sc=1560 on 16-12-2018.

General Impacts
Najas minor establishes dense monocultures that may exclude other native aquatic plants and replaces native Najas species. Unlike some of the other invasive aquatic plants N. minor does not produce long stems that spread on the surface of the water; it grows very densely under the surface producing shoots upto a meter long that shade out other plants and interfere with recreational activity such as swimming, boating, and fishing and reduce the aesthetic value of waters. It is also believed to induce conditions that are adverse to fish and waterfowl. N. minor may reduce the discharge capacity of channels as well. Its negative effects are typically amplified in enriched, low-energy systems (DNR, 2007; Hellquist & Straub, 2002; Cao, 2010; Capers et al, 2005).
Management Info
Preventative measures: Najas minor is reported as noxious and is regulated in Alabama, Connecticut, Maine, Massachusetts, New Hampshire, South Carolina, Washington. It is illegal to possess, import, purchase, sell, propogate, transport, or introduce N. minor in Minnesota. N. minor was included on a Washington Department of Agriculture list of quarantined species in 2000, and it is illegal to sell, trade, or transport in the state of Washington. Education and population monitoring are recommended to help prevent its establishment (DNR, 2007; Hamel & Parsons, 2001).

Chemical: Small scale herbicide treatments of endothall, dipotassium, and endothall mono have been conducted in hopes to provide “nuisance relief.” However, it has been reported that some non-target plant species have been affected as well. The following herbicides and brands were reported to yield excellent control for N. minor by the US army Corp of Engineers: diquat: Reward, Weedtrine-D; fluridone: Sonar AS, Sonar SRP, Sonar PR, Sonar Q, and Avast!; and endothall Aquathol K, Aquathol Super K, Hydrothol 191. N. minor was found to be completely unaffected by the herbicide butachlor (DNR, 2007; EL-EDRC, undated; Chattopadhyay et al, 2006).

Mechanical: The use of aquatic plant harvesters, large boats that cut and remove vegetation, has been recommended as a means to remove large quantities of Najas minor. Similarly, rotovators, basically large underwater rototillers that remove aquatic plant tissue and root crowns, are another recommended mechanical control. The use of hand cutters may be effective for smaller populations (EL-ERDC, undated).

Countries (or multi-country features) with distribution records for Najas minor
ALIEN RANGE
NATIVE RANGE
  • austria
  • belgium
  • bulgaria
  • czech republic
  • france
  • germany
  • hungary
  • india
  • italy
  • japan
  • morocco
  • poland
  • portugal
  • romania
  • russian federation
  • serbia and montenegro
  • turkey
  • ukraine
Informations on Najas minor has been recorded for the following locations. Click on the name for additional informations.
Lorem Ipsum
Location Status Invasiveness Occurrence Source
Details of Najas minor in information
Status
Invasiveness
Arrival date
Occurrence
Source
Introduction
Species notes for this location
Location note
Management notes for this location
Impact
Mechanism:
Outcome:
Ecosystem services:
Impact information
Najas minor establishes dense monocultures that may exclude other native aquatic plants and replaces native Najas species. Unlike some of the other invasive aquatic plants N. minor does not produce long stems that spread on the surface of the water; it grows very densely under the surface producing shoots upto a meter long that shade out other plants and interfere with recreational activity such as swimming, boating, and fishing and reduce the aesthetic value of waters. It is also believed to induce conditions that are adverse to fish and waterfowl. N. minor may reduce the discharge capacity of channels as well. Its negative effects are typically amplified in enriched, low-energy systems (DNR, 2007; Hellquist & Straub, 2002; Cao, 2010; Capers et al, 2005).
Red List assessed species 0:
Locations
CANADA
UNITED STATES
Mechanism
[1] Competition
Outcomes
[4] Environmental Ecosystem - Habitat
  • [1] Modification of nutrient pool and fluxes
  • [2] Reduction in native biodiversity
  • [1] Physical disturbance
[1] Environmental Species - Population
  • [1] Reduces/inhibits the growth of other species
[3] Socio-Economic
  • [1] Human nuisance 
  • [1] Alteration of recreational use and tourism
  • [1] Limited access to water, land and other
Management information
Preventative measures: Najas minor is reported as noxious and is regulated in Alabama, Connecticut, Maine, Massachusetts, New Hampshire, South Carolina, Washington. It is illegal to possess, import, purchase, sell, propogate, transport, or introduce N. minor in Minnesota. N. minor was included on a Washington Department of Agriculture list of quarantined species in 2000, and it is illegal to sell, trade, or transport in the state of Washington. Education and population monitoring are recommended to help prevent its establishment (DNR, 2007; Hamel & Parsons, 2001).

Chemical: Small scale herbicide treatments of endothall, dipotassium, and endothall mono have been conducted in hopes to provide “nuisance relief.” However, it has been reported that some non-target plant species have been affected as well. The following herbicides and brands were reported to yield excellent control for N. minor by the US army Corp of Engineers: diquat: Reward, Weedtrine-D; fluridone: Sonar AS, Sonar SRP, Sonar PR, Sonar Q, and Avast!; and endothall Aquathol K, Aquathol Super K, Hydrothol 191. N. minor was found to be completely unaffected by the herbicide butachlor (DNR, 2007; EL-EDRC, undated; Chattopadhyay et al, 2006).

Mechanical: The use of aquatic plant harvesters, large boats that cut and remove vegetation, has been recommended as a means to remove large quantities of Najas minor. Similarly, rotovators, basically large underwater rototillers that remove aquatic plant tissue and root crowns, are another recommended mechanical control. The use of hand cutters may be effective for smaller populations (EL-ERDC, undated).

Bibliography
32 references found for Najas minor

Managment information
Department of Natural Resources (DNR), Wisconsin, 2007. Aquatic Plant Brittle/Lesser/Bushy/Slender/Spiny/Minor Naiad; Waternymph
Environmental Laboratory (EL) U.S. Army Engineer Research and Development Center (ERDC), 2007. Najas minor All. (Slender Naiad) Herbicide Information
Environmental Laboratory (EL) U.S. Army Engineer Research and Development Center (ERDC), 2007. Najas minor All. (Slender Naiad) Mechanical Control Information
Environmental Laboratory (EL) U.S. Army Engineer Research and Development Center (ERDC), 2007. Information Sheet: Najas minor L. (Spiny Naiad)
National Agricultural Pest Information System (NAPIS), 2010. Pest Tracker Reported Status of Brittle Naiad - Najas minor
Summary: Available from: http://pest.ceris.purdue.edu/searchmap.php?selectName=PDJABBE [Accessed November 16 2009]
Richardson, Robert J., 2008. Aquatic Plant Management and the Impact of Emerging Herbicide Resistance Issues. Weed Technology 2008 22:8�15
The Nature Conservancy (TNC), 2009. Invasive Plant Distribution Map Ohio: Najas minor Lesser naiad
Vermont Invasive Exotic Plant Committee, February 18, 2005. Vermont�s Wildlife Action Plan: Invasive Species Watch List for Vermont. Appendix K Exotic Invasive & Pest Species
Summary: Available from: http://www.vtfishandwildlife.com/library/Reports_and_Documents/Vermonts_Wildlife_Action_plan/_/_report/7_Appendix/K_Invasive_Exotic_and_Pest_Species.pdf [Accessed November 16 2009]
General information
Alan, W. Wentz and Ronald L. Stuckey., 1971. The Changing Distribution of the Genus Najas (Najadaceae) in Ohio. The Ohio Journal of Science 71(5): 292, September 1971
Bruinsma, J.H.P. 1994. The occurrence of Najas minor All. in the Eindhovenkanaal in 1992 and 1993 [Het voorkomen van Najas minor All. (Klein nimfkruid) in het Eindhovens Kanaal in 1992 en 1993]. Gorteria: Tijdschrift voor Onderzoek aan de Wilde Flora Volume 20, Issue 1, 1994, Pages 18-27 .
Cao, Ling, 2010. Najas minor. USGS Nonindigenous Aquatic Species Database, Gainesville, FL.
Capers, Robert S., Gregory J. Bugbee, Roslyn Selsky and Jason C. White, 2005. A Guide to Invasive Aquatic Plants of Connecticut. The Connecticut Agricultural Experiment Station Bulletin 997 January 2005
Capers, Robert S., Roslyn Selsky, Gregory J. Bugbee, Jason C. White, 2007. Aquatic Plant Community Invasibility and Scale Dependent Patterns in Native and Invasive Species Richness. Ecology: Vol. 88, No. 12, pp. 3135-3143.
Global Compendium of Weeds (GCW), 2007. Najas minor (Najadaceae)
Summary: Available from: http://www.hear.org/gcw/species/najas_minor/ [Accessed November 16 2009]
Hamel, Kathy, S & Jenifer K. Parsons, 2001. Washington s Aquatic Plant Quarantine. J. Aquat. Plant Manage. 39: 72-75
Summary: Available from: http://www.sgnis.org/publicat/papers/hamepars.pdf [Accessed November 16 2009]
Hellquist, C. Barre & James Straub, 2002. A Guide to Selected Invasive Non-native Aquatic Species in Massachusetts
Summary: Available from: http://www.fosterspond.com/aquatic_species.pdf [Accessed November 16 2009]
Integrated Taxonomic Information System (ITIS), 2010. Najas minor All.
Summary: Available from: http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=39002 [Accessed November 16 2009]
Les, D.H. and Mehrhoff, L. J. 1999. Introduction of nonindigenous aquatic vascular plants in southern New England: a historical perspective. Biological Invasions 1: 281�300, 1999.
Lowden, Richard M. 1986. Taxonomy of the genus Najas L. (Najadaceae) in the Neotropics. Aquatic Botany, 24 (1986) 147-184.
Maryland Department of Natural Resources (MDNR), Undated. Naiads Najas spp.
Summary: Available from: http://www.dnr.state.md.us/bay/SAV/key/naiads.pdf [Accessed November 16 2009]
Rybicki, Nancy B; Landwehr, Jurate M., 2007. Long-term changes in abundance and diversity of macrophyte and waterfowl populations in an estuary with exotic macrophytes and improving water quality. Limnology & Oceanography. 52(3). MAY 2007. 1195-1207.
Trebitz, Anett S; Taylor, Debra L., 2007. Exotic and invasive aquatic plants in Great Lakes coastal wetlands: Distribution and relation to watershed land use and plant richness and cover. Journal of Great Lakes Research. 33(4). DEC 2007. 705-721.
Trebitz, A.S., Taylor, D.L. 2007. Exotic and invasive aquatic plants in Great Lakes coastal wetlands: Distribution and relation to watershed land use and plant richness and cover. Journal of Great Lakes Research 33 (4), pp. 705-721.
Zalewska, Joanna. 1999. The genus Najas (Najadaceae) in Poland: Remarks on taxonomy, ecology, distribution and conservation. Fragmenta Floristica et Geobotanica. 44(2). 1999. 401-422.
Contact
The following 1 contacts offer information an advice on Najas minor
Capers,
Robert S.
Organization:
Plant collections manager, George Safford Torrey Herbarium, Department of Ecology and Evolutionary Biology, University of Connecticut
Address:
75 N. Eagleville Road, Unit 3043, Storrs, CT 06269-3043, U.S.A.
Phone:
860-486-1889
Fax:
860-486-6364