Identification, Biology and Management of Elodea canadensis ...

when the weed will disperse into areas unfavourable to itssurvival.Draining. Hejny and Husák (1978) comment that controlin Czechoslovakia is simply effected by a combination ofsummer and winter drainage. Winter frost also helps in theseclimates. In Australia, control is aided by draining and exposureof sediments to high summer temperatures or winterfrosts, but draining for sufficient time is not always feasible,especially in larger canals.Herbicides. E. canadensis is difficult to control with herbicides.Possible explanations include the protective effect ofheavy coatings of bacteria and aufwuchs (detritus, algae, bacteriaand inorganic particulates) on the leaves of the plants.The role of bacteria in protecting E. canadensis against diquatwas demonstrated by Whitfort (1982) using plants grownaxenically or colonized by Pseudomonas or Bacillus spp. Similarly,Bowmer (1982b) demonstrated that aufwuchs washedfrom the leaves of E. canadensis would contribute to the lossof toxic effect.Another problem is the difficulty of penetrating verydense weed beds with herbicides as described by Bowmer etal. (1985) in their attempts to control E. canadensis with terbutryne.Several herbicides seem to require long contacttimes for effective control, for example, fluridone (1-methyl-3-phenyl-5-[3-(trifluromethyl) phenyl]-4(1H)-pyridinone),endothal (7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid)and terbutryne (2-(tert-butylamine)-4-(ethylamino)-6-(methyl-thio)-s-triazine). This makes management difficultin flowing water. Herbicides preferred for their margins ofsafety for water users and aquatic life (for example the potassiumsalt of endothal) seem to be ineffective.Diquat (6,7-dihydrodipyrido[1,2-∝:2,1-c]pyrazinediium) andcopper sulphate or chelates of copper can be used in static water.The addition of copper is reputed to improve control comparedwith diquat alone, and is also advantageous because algae areinhibited. Paraquat (1,1 1 -dimethyl-4,4 1 -bipyridinium(I)) anddiquat mixtures are used in Czechoslovakia, but these promote thesubsequent growth of filamentous algae. Diquat is ineffective inturbid waters because it is inactivated by adsorption to soil particles(Bowmer 1982a).Elodea canadensis, Egeria densa and Hydrilla verticillata areknown to be sensitive to fluridone (McCorkelle et al. 1992a).But reliable control requires static water and the total treatmentof a pond or lake. In slow-moving water the effectivenessof fluridone is reduced. Label recommendations arethat water bodies should be maintained static for at leastseven days after treatment to enable adequate uptake of herbicideby the plants. Use of fluridone in the irrigation channelsystems of Australia may be limited because of potentialdamage to susceptible crops, especially rice.Terbutryne is used for control of various submergedweeds including E. canadensis in Europe (Murphy 1982), andin Ontario (MacKenzie et al. 1983). For treatment of lakesand storages this compound has many advantages, whichinclude longer-term control of macrophytes, suppression ofalgae, and greater safety for non-target aquatic organismsincluding fish (Aston and Reynaert 1974). It has been consideredfor use in temperate lakes for control of Myriophyllumspicatum, but not Elodea canadensis. Treatment of flowingwater would be impractical because of the extensive contactFigure 5. Distribution of Elodea bifoliata (•), Elodea nuttallii (°) and Elodeacanadensis (▲) in North America (modified from Cook and Urmi-König 1985).time required for the herbicide to be effective (Bowmer et al.1985).Acrolein (acrylaldehyde) gives temporary control in flowingwater. It is injected into the water and allowed to flowover the weed beds. Application is restricted to approvedoperators. It is used in several States of North America,mainly in the Pacific Northwest, for treatment of a mixedspectrum of submerged weeds in irrigation distribution systems.In Australia, the sensitivity of different species in a trialwas Vallisneria spp. >Elodea canadensis >Potamogeton tricarinatus.Therefore repeated treatment may disadvantage thedesirable native Vallisneria, and favour the troublesome andobstructive native Potamogeton (Bowmer and Smith 1984).The optimisation of acrolein use, including the economy ofmultiple additions to compensate for rapid loss from flowingwater, is described by Bowmer and Sainty (1977).Bensulfuron methyl (Methyl 2[[[[[(4,6 dimethoxy pyrimidin-2-yl)amine]carbonyl]amino]sulfonyl]methyl]benzoate)showed great potential for control of Hydrilla verticillata byinhibiting tuber formation (Anderson and Dechoretz 1988).In Australia, Elodea canadensis is tolerant to bensulfuronmethyl (McCorkelle et al. 1992b). Bensulfuron methyl is theactive ingredient of both Londax ® , a herbicide used in riceproduction, and Mariner ® , a herbicide that was under evaluationfor use in aquatic environments. In late 1992, work onthe registration of Mariner ® was stopped because it had accumulatedtemporarily in freshwater clams, a monitoringorganism (Anon 1992).Other herbicides reported to be used in managementinclude:(i) for injection into flowing water: aromatic solvent andemulsifier; anhydrous ammonia; copper sulphate (dumpedor continuously fed into the water); and the liquid formulationof endothal alkylamine.(ii) for treatment of ponded water: ametryn (2-ethylamino-4-isopropylamino-6-methyl thio-1,3,5-triazine); anhydrousammonia; copper sulphate; endothal alkylamine (liquid orgranular formulations); hexazinone (3-cyclohexyl-6-(dimeth-J. Aquat. Plant Manage. 33: 1995. 17

ylamino)-1-methyl-1,3,5,triazine-2,4(1H,3H)-dione);simazine (2-chloro-4,6-bis(ethylamino)-s-triazine); and terbutrynegranules.(iii) for use as soil residual herbicides, after channel drainage:chlorfenac (dichlobenil(2,6-dichlorobenzonitrile); andsimazine.Many of these herbicides are no longer permitted for usein most aquatic situations (e.g. chlorfenac, hexazinone).Some are of doubtful efficacy (e.g. dichlobenil used as a soilresidual herbicide) and all are restricted by situation andwater use. The subject was reviewed by Bowmer et al. (1979)and Bowmer (1987).ACKNOWLEDGMENTSWe are grateful to Mike Boulton and Laurie Jackel forinformation on the distribution and importance of Elodeacanadensis.LITERATURE CITEDAnderson, L.W.J. and N. Dechoretz. 1988. Bensulfuron methyl: A new herbicide.In: Proceedings, 22nd Annual Meeting, Aquatic Plant ControlResearch Program, 16-19 November 1987, Portland Oregon, EnvironmentalLaboratory, US Army Engineers Waterways Experiment Station,Vicksburg, MS pp. 224-235.Anonymous. 1992. Du Pont halts work on Mariner, Aquaphyte, University ofFlorida, Gainesville, p. 2.Aston, H.I. 1973. Aquatic Plants of Australia. Melbourne University Press,pp. 216-217.Aston, J.L. and J. Reynaert, J. 1974. The current and potential use of the triazineherbicides in water. Proceedings of the EWRS 4th Symposium onAquatic Weeds, pp. 244-252.Bonar, S.A., G.L. Thomas, and G.B. Pauley. 1987. Estimation of triploidWhite Amur stocking densities for aquatic plant control for Devils Lake,Oregon, Proceedings 21st Annual Meeting Aquatic Plant controlResearch Program, Miscellaneous Paper A-87-2, US Army EngineerWaterways Experiment Station, Vicksburg, Mississippi, pp. 122-132.Bowes, G. and M.E. Salvucci. 1989. Plasticity in the photosynthetic carbonmetabolism of submersed aquatic macrophytes. Aquat. Bot. 34:233-266.Bowers, K.L., G.B. Pauley, and G.L. Thomas. 1987. Feeding preference onPacific Northwest aquatic plant species by diploid and triploid GrassCarp (Ctenopharyngodon idella). Proceedings 21st annual Meeting AquaticPlant Control Research Program, Miscellaneous Paper A-87-2, US ArmyEngineer Waterways Experiment Station, Vicksburg, Mississippi, pp. 133-140.Bowmer, K.H. 1982a. Adsorption characteristics of seston in irrigation water:implication for the use of aquatic herbicides. Aust J Mar Freshwater Res,33:443-458.Bowmer, K.H. 1982b. Aggregates of particulate matter and aufwuchs on Elodeacanadensis in irrigation waters, and inactivation of diquat. Aust J MarFreshwater Res, 33:589-593.Bowmer, K.H. 1987. Herbicides in surface water. In: Herbicides, D.H. Hutsonand T.R. Roberts, eds., John Wiley & Sons Ltd, Chichester, pp. 271-355.Bowmer, K.H., D.S. Mitchell, and D.L. Short. 1984. Biology of Elodeacanadensis Mich. and its management in Australian irrigation systems.Aquat. Bot. 18:231-238.Bowmer, K.H. and G.R. Sainty. 1977. Management of aquatic plants withacrolein. J. Aquat. Plant Manage. 15:40-46.Bowmer, K.H., G.R. Sainty, G. Smith and K. Shaw 1979. Management of Elodeain Australian irrigation systems. J. Aquat. Plant Manage. 17:4-12.Bowmer, K.H., K. Shaw and J.A. Adeney. 1985. Management of submergedaquatic macrophytes with terbutryne: availance, phytotoxicity and persistence.Weed Res. 25:449-459.Bowmer, K.H. and G.H. Smith. 1984. Herbicides for injection into flowingwater: acrolein and endothal-amine. Weed Res. 24:201-211.Brown, J.M.A., F.I. Dromgoole, M.W. Towsey, and J. Browse. 1974. Photosynthesisand photorespiration in aquatic macrophytes. In: Mechanisms ofRegulation of Plant Growth, R.L. Bieliski, A.R. Ferguson, and M.M.Cresswell, eds., The Royal Society of New Zealand, Wellington, pp. 243-249.Burrows, D. 1993. ASL Newsletter 31(1),58.Cook, C.D.K. 1982. Pollination mechanisms in the Hydrocharitaceae. In:Studies on Aquatic Vascular Plants, J.J Symoen, S.S. Hooper and P. Compère,eds., Royal Botanical Society of Belgium, Brussels, pp. 1-15.Cook, C.D.K. and K. Urmi-König. 1985. A revision of the genus Elodea(Hydrocharitaceae). Aquat. Bot. 21:111-156.Correll, D.S. and H.B Correll. 1975. Aquatic and Wetland Plants of SouthwesternUnited States, University Press, Stanford, California, pp. 163-167.Fowler, M.C. and T.O. Robson. 1978. The effects of the food preferencesand stocking rates of grass carp (C. idella) on mixed plant communities.Aquat. Bot. 5:261-276.Godshalk, G.L., J.W. Barko, and W.F. James. 1987. Effects of submersedaquatic plants on their environment. Proceedings 21st Annual MeetingAquatic Plant Control Research Program, Miscellaneous Paper A-87-2,US Army Engineer Waterways Experiment Station, Vicksburg, Mississippi,pp. 215-224.Haramoto, T. and Ikusima, I. 1988. Life cycle of Egeria densa Planch., anaquatic plant naturalized in Japan. Aquat. Bot. 30:389-403.Hejny, S. and S. Husák. 1978. In: Pond Littoral Ecosystems Structure andFunctioning, D. Dykyjová and J. Kvet, eds. Springer-Verlag, Berlin, pp.36-37.Howard-Williams, C. and W.F. Vincent. 1983. Plants of the littoral zone. InLake Taupo: ecology of a New Zealand lake, D.J. Forsyth and C. Howard-Williams, eds., Science Information Publishing Centre, Department ofScientific and Industrial Research, Wellington, New Zealand. pp.73-84.Hughes, H.R. 1976. Research into aquatic weeds in New Zealand waterways:a review. DSIR Information Series No. 116, N.Z. Department of Scientificand Industrial Research, 34pp.Keeley, J.E. 1990. Photsynthetic pathways in freshwater aquatic plants.Trends in Ecology and Evolution 5:330-333.Kelly, G.J. and E. Latzko. 1982. IV. Photosynthesis. Carbon metabolism: theprofound effects of illumination on the metabolism of photosyntheticcells. Prog Bot 44:103-131.Maberly, S.C. 1983. The interdependence of photon irradiance and free carbondioxide or bicarbonate concentration on the photosynthetic compensationpoints of freshwater plants. New Phytol. 93:1-12.Maberly, S.C. and D.H.N. Spence. 1983. Photosynthetic inorganic carbonuse by freshwater plants. J. Ecol. 77:705-724.Mason, R. 1975. The Macrophytes. In: New Zealand Lakes V.H. Jolly andJ.M.A. Brown, eds., Auckland University Press; Oxford University Press,pp. 239-240.Mackenzie, D., R. Frank, and G.J. Sirons. 1983. Aquatic plant control anddisappearance of terbutryne from treated waters in Ontario, Canada1974-1977. J. Aquat. Plant Manage. 21:11-16.McCorkelle, G., G.R. Sainty and K.H. Bowmer. 1992a. Evaluation of Sonar(Fluridone) for aquatic plant management in Australia. Final report forDow Elanco Australia Ltd, Consultancy Report No 92/2. CSIRO Divisionof Water Resources, Griffith NSW. 58pp.McCorkelle, G., G.R. Sainty and K.H. Bowmer. 1992b. Use of Bensulfuron inirrigation supply systems in Australia. Report for Du Pont (Australia)Ltd, Consultancy report No 93/43. CSIRO Division of Water Resources,Griffith NSW. 20pp.Mues, R. 1983. Species specific flavone glucoronides in Elodea species. BiochemSyst Ecol 11:261-265.Murphy, K.J. 1982. The use of methylthiotriazines in fresh-water systems: areview. Proceedings of the EWRS 6th Symposium on Aquatic Weeds, pp.263-277.Olsen, C. 1954. Mvilke betingelser ma voere opfyldte for at Elodea canadensiskan opna den optimale udvikling, der er arsag til dens masseviseoptraeden in naturen? [What are the conditions of optimum developmentenabling Elodea canadensis to grow profusely in nature?] BotaniskTidsskrift 51: 271-273.Pauley, G.B., G.L. Thomas, S.L. Thiesfeld. S.A. Bonar, and K.L. Bowers.1987. An overview of the use of triploid Grass Carp (Ctenopharyngodonidella) as a biological control of aquatic macrophytes in Devils Lake, Oregon,Proceedings 21st Annual Meeting Aquatic Plant Control Research18 J. Aquat. Plant Manage. 33: 1995.

Program, Miscellaneous Paper A-87-2, US Army Engineer WaterwaysExperiment Station, Vicksburg, Mississippi, pp. 115-121.Prins, H.B.A., J.F.H. Snel, and P.E. Zanstra. 1982. The mechanism of photosyntheticbicarbonate utilization. In: Studies on Aquatic Vascular Plants,J.J. Symoens and S.S. Hoor, eds., Royal Botanical Society of Belgium, pp.120-126.Rørslett, B., D. Berge, and S.W. Johansen. 1985. Mass invasion of Elodeacanadensis in a mesotrophic, South Norwegian lake - impact on waterquality. Verh. Internat. Verein. Limnol. 22:2920-2926.Sainty, G.R. and S.W.L. Jacobs. 1981. Waterplants of New South Wales. WaterResources Commission of New South Wales. 550pp.Sainty, G.R. and S.W.L. Jacobs. 1988. Waterplants in Australia, Sainty & Associates.Sydney, pp. 65-71.Sculthorpe, C.D. 1967. The Biology of Aquatic Vascular Plants, EdwardArnold, London, 610 pp.Simpson, D.A. 1984. A short history of the introduction and spread of ElodeaMichx in the British Isles. Watsonia 15:1-9.Taylor, M.E.U. 1971. A study of elodea growth in some low-nutrient lakes. In:Symposium on Natural Water Quality and Waste Treatment Technology,Massey University, New Zealand, pp. 27-38.US Army Corps of Engineers. 1987. Proceedings 21st Annual MeetingAquatic Plant Control Research Program, Miscellaneous Paper A-87-2,US Army Engineer Waterways Experiment Station, Vicksburg, Mississippi,pp. 5-30.Whitfort, L.A. 1982. Investigations into the composition of epiphytic communitiesand their influence on the uptake of diquat by Elodea canadensisRich. MSc. Thesis, University of New South Wales; CSIRO Division ofIrrigation Research, Griffith, New South Wales, 132 pp.J. Aquat. Plant Manage. 33: 19-22Waterbird Abundance and Activity onWaterhyacinth and Egeriain the St. Marks River, FloridaABSTRACTWaterbird densities and activities were quantified on twononnative plant species, waterhyacinth and egeria, in a northFlorida coastal plain river. Individual waterhyacinth mats andegeria plots were marked in three successive river sections,and birds were viewed weekly from 7 July to 20 September1991. Total bird densities and counts for individual specieswere similar between plant species on all observation dates(P>0.05). The Little blue heron, Common moorhen, and theTricolored heron were the most common species and foragingwas the primary activity on both plant species. Birds stalkingin waterhyacinth most often obtained prey located nearthe perimeter of mats, and rarely hunted for food in the interiorof mats.Key words: coastal river, nonnative plant, Little blue heron,Tricolored heron, Common moorhen, bird foraging.INTRODUCTIONBird distributions within water-bodies are often related toprey densities and the ability of individual species, through1 Florida Department of Environmental Protection, Bureau of AquaticPlant Management, 3917 Commonwealth Boulevard, Tallahassee, Florida32399, USA. Received for publication March 28, 1994 and in revised formJanuary 4, 1995.2 Collopy, M. W. and H. L. Jelks. 1989. Distribution of foraging wadingbirds in relation to the physical and biological characteristics of freshwaterwetlands in southwest Florida. Florida Game and Fresh Water Fish Comm.Nongame Wildl. Prog. Final Rep. Tallahassee, FL. 102pp.WILLIAM BARTODZIEJ AND G. WEYMOUTH 1specialized adaptations, to efficiently capture prey (Jenni1969, Kushlan 1973, Willard 1977, Kushlan 1978). Aquaticvegetation, which commonly harbors invertebrate and vertebrateprey, is generally considered a more favorable foraginghabitat than deep, open-water areas. In terms of waterbirdforaging success, certain vegetation communities may providebetter hunting grounds than others (Zaffke 1984) 2 .Little if any data exists on waterbird abundance andbehavior on river plants found in Florida. The purpose ofthis study was to quantify bird densities and record bird activitieson the nonnative egeria (Egeria densa Planchon) andwaterhyacinth [Eichhornia crassipes (Mart.) Solms].STUDY SITEThe St. Marks River (30° 16'N, 84° 08'W), located in akarst area of Wakulla County, Florida, is spring-fed and flowsfor approximately 30 km through flat coastal woodlands. In1988, the Florida Legislature passed a moratorium on herbicideapplications to control aquatic vegetation, primarilywaterhyacinth, in this river. That action resulted in ananthropogenically undisturbed, but naturally dynamic plantcommunity in which to observe bird abundance and behavior.Since 1988, the waterhyacinth population has expanded,with frequency-of-occurrence estimates varying from 5 to 15percent during the 1989-1992 growing seasons 3 . Althoughwaterhyacinth has the ability to double its biomass (wetweight) in 14 days in unshaded parts of the river, weobserved that floods act as a natural control mechanismJ. Aquat. Plant Manage. 33: 1995. 19

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