Recent Submissions

  • Panel Discussion - Management of Eurasian watermilfoil in the United States using native insects: State regulatory and management issues

    Madsen, John D.; Crosson, H. A.; Hamel, K. S.; Hilovsky, M. A.; Welling, C. H. (2000)
    While researchers have evaluated the potential of nativeinsect herbivores to manage nonindigenous aquatic plantspecies such as Eurasian watermilfoil (Myriophyllum spicatumL.), the practical matters of regulatory compliance and implementationhave been neglected. A panel of aquatic nuisancespecies program managers from three state naturalresource management agencies (Minnesota, Vermont andWashington) discussed their regulatory and policy concerns.In addition, one ecological consultant attempting to marketone of the native insects to manage Eurasian watermilfoiladded his perspective on the special challenges of distributinga native biological control agent for management of Eurasianwatermilfoil.
  • Relationship between water quality, watermilfoil frequency, and weevil distribution in the State of Washington

    Tamayo, Mariana; Grue, Christian E.; Hamel, Kathy (2000)
    During the summer of 1997, we surveyed 50 waterbodiesin Washington State to determine the distribution of theaquatic weevilEuhrychiopsis leconteiDietz. We collected dataon water quality and the frequency of occurrence of watermilfoilspecies within selected watermilfoil beds to comparethe waterbodies and determine if they were related to thedistribution E. lecontei. We foundE. leconteiin 14 waterbodies,most of which were in eastern Washington. Only one lakewith weevils was located in western Washington. Weevils wereassociated with both Eurasian (Myriophyllum spicatumL.) andnorthern watermilfoil (M. sibiricumK.). Waterbodies withE.leconteihad significantly higher (P< 0.05) pH (8.7±0.2)(mean±2SE), specific conductance (0.3±0.08 mS cm-1) andtotal alkalinity (132.4±30.8 mg CaCO3L-1). We also foundthat weevil presence was related to surface water temperatureand waterbody location ( = 24.3,P≤0.001) and of allthe models tested, this model provided the best fit (Hosmer-Lemeshow goodness-of-fit = 4.0,P= 0.9). Our results suggestthat in Washington StateE. leconteioccurs primarily ineastern Washington in waterbodies with pH≥8.2 and specificconductance≥0.2 mS cm-1. Furthermore, weevil distributionappears to be correlated with waterbody location (easternversus western Washington) and surface water temperature.
  • Factors to consider when using native biological control organisms to manage exotic plants

    Cofrancesco, Alfred F. (2000)
    Biological control of exotic plant populations with nativeorganisms appears to be increasing, even though its successto date has been limited. Although many researchers andmanagers feel that native organisms are easier to use andpresent less risk to the environment this may not be true.Developing a successful management program with a nativeinsect is dependent on a number of critical factors that needto be considered. Information is needed on the feeding preferenceof the agent, agent effectiveness, environmental regulationof the agent, unique requirements of the agent,population maintenance of the agent, and time to desiredimpact. By understanding these factors, researchers andmanagers can develop a detailed protocol for using the nativebiological control agent for a specific target plant.. We foundE. leconteiin 14 waterbodies,most of which were in eastern Washington. Only one lakewith weevils was located in western Washington. Weevils wereassociated with both Eurasian (Myriophyllum spicatumL.) andnorthern watermilfoil (M. sibiricumK.). Waterbodies withE.leconteihad significantly higher (P< 0.05) pH (8.7±0.2)(mean±2SE), specific conductance (0.3±0.08 mS cm-1) andtotal alkalinity (132.4±30.8 mg CaCO3L-1). We also foundthat weevil presence was related to surface water temperatureand waterbody location ( = 24.3,P≤0.001) and of allthe models tested, this model provided the best fit (Hosmer-Lemeshow goodness-of-fit = 4.0,P= 0.9). Our results suggestthat in Washington StateE. leconteioccurs primarily ineastern Washington in waterbodies with pH≥8.2 and specificconductance≥0.2 mS cm-1. Furthermore, weevil distributionappears to be correlated with waterbody location (easternversus western Washington) and surface water temperature.
  • Euhrychiopsis lecontei distribution, abundance, and experimental augmentations for Eurasian watermilfoil control in Wisconsin lakes

    Jester, Laura L.; Bozek, Michael A.; Helsel, Daniel R.; Sheldon, Sallie P. (2000)
    The specialist aquatic herbivore Euhrychiopsis lecontei (Dietz)is currently being researched as a potential biological controlagent for Eurasian watermilfoil (Myriophyllum spicatum L.).Our research in Wisconsin focused on 1) determining milfoilweevil distribution across lakes, 2) assessing limnologicalcharacteristics associated with their abundance, and 3) evaluatingmilfoil weevil augmentation as a practical managementtool for controlling Eurasian watermilfoil.
  • A decline of Eurasian watermilfoil in Minnesota associated with the milfoil weevil, Euhrychiopsis lecontei

    Newman, Raymond M.; Biesboer, David D. (2000)
    Euhrychiopsis leconteiRAYMOND M. NEWMAN1AND DAVID D. BIESBOER2ABSTRACTThe native milfoil weevil,Euhrychiopsis leconteiDietz, is acandidate biological control agent for the exotic Eurasianwatermilfoil (Myriophyllum spicatumL.) in northern NorthAmerica. Declines of Eurasian watermilfoil populations havebeen associated with the weevil but many of these examplesare poorly documented. We report the first documented declineof Eurasian watermilfoil in Minnesota due to the milfoilweevil.
  • Eurasian watermilfoil biomass associated with insect herbivores in New York

    Johnson, Robert L.; Van Dusen, Peter J.; Toner, Jason A.; Hairston, Nelson G. (2000)
    A study of aquatic plant biomass within Cayuga Lake, NewYork spans twelve years from 1987-1998. The exotic Eurasianwatermilfoil(Myriophyllum spicatumL.) decreased in thenorthwest end of the lake from 55% of the total biomass in1987 to 0.4% in 1998 and within the southwest end from50% in 1987 to 11% in 1998. Concurrent with the watermilfoildecline was the resurgence of native species of submersedmacrophytes. During this time we recorded for thefirst time in Cayuga Lake two herbivorous insect species: theaquatic mothAcentria ephemerella, first observed in 1991, andthe aquatic weevilEuhrychiopsis lecontei, first found in 1996.Densities ofAcentriain southwest Cayuga Lake averaged 1.04individuals per apical meristem of Eurasian watermilfoil forthe three-year period 1996-1998. These same meristems hadEuhrychiopsisdensities on average of only 0.02 individuals perapical meristem over the same three-year period. A comparisonof herbivore densities and lake sizes from five lakes in1997 shows thatAcentriadensities correlate positively withlake surface area and mean depth, whileEuhrychiopsisdensitiescorrelate negatively with lake surface area and meandepth. In these five lakes,Acentriadensities correlate negativelywith percent composition and dry mass of watermilfoil.However,Euhrychiopsisdensities correlate positively with percentcomposition and dry mass of watermilfoil. Finally,Acentriadensities correlate negatively withEuhrychiopsisdensitiessuggesting interspecific competition.
  • Temporal and spatial changes in milfoil distribution and biomass associated with weevils in Fish Lake, WI

    Jester, Laura L.; Bozek, Michael A.; Helsel, Daniel R.; Sheldon, Sallie P. (2000)
    During the course of an eight year monitoring effort, theWisconsin Department of Natural Resources documented asignificant decline in milfoil biomass and distribution in FishLake, Wisconsin. Average milfoil biomass declined by 40-50% from 374-524 g dw m-2during 1991-93 to 265 g dw m-2during both 1994 and 1995. Milfoil recovered fully in 1996-98 to 446- 564 g dw m-2. The size of the milfoil bed, as discernedfrom aerial photographs, shrank from a maximumcoverage of 40 ha in 1991 to less than 20 ha during 1995.During the “crash” of 1994-95, milfoil plants exhibited typicalsigns of weevil-induced damage, including darkened, brittle,hollowed-out growing tips, and the arching and collapseof stems associated with loss of buoyancy. Monitoring of weevilsand stem damage during 1995-98 showed highest densitiesand heaviest damage occurred near shore and subsequentlyfanned out into deeper water from core infestationsites each spring. The extent of milfoil stem damage was positivelycorrelated with weevil densities (monthly sampling).However, weevil densities and stem damage were lower during1995 (when milfoil biomass was in decline) than during1996-98 (when milfoil biomass was fully recovered).
  • Herbicide evaluation for the control of wild taro

    Nelson, Linda A.; Getsinger, Kurt D. (2000)
    Wild taro (Colocasia esculenta (L.) Schott), is an exotic, emergentperennial that has established in many shallow-waterwetlands throughout the southern United States. Althoughwild taro is a cultivated crop in many tropical and subtropicalareas of the world, its invasion in riverine and lacustrine wetlandsin the U.S. has resulted in the loss of habitat for nativeplant species. Once established, wild taro forms dense, monotypicstands that reduce the diversity of native vegetation, ashas occurred in Louisiana, Florida, and Texas (Akridge andFonteyn 1981, Simberloff et al. 1997). Akridge and Fonteyn(1981) reported that although wild taro is considered naturalizedin south-central Texas, its present dominance alongthe San Marcos River has altered the native vegetationalstructure and dynamics of this river system. Theobjective of this study was to evaluate the efficacy of fouraquatic herbicides for control of wild taro.
  • Relative tolerance of mat-forming algae to copper

    Lembi, Carole A. (2000)
    This study documents the relative tolerance of the common,weedy mat-forming green algaeHydrodictyon,Oedogonium,Pithophora,Rhizoclonium, andSpirogyrato copper. In addition,the copper tolerance of the cyanobacterial (blue-green algal)mat-formingOscillatoriawas assessed.
  • The weevil-watermilfoil interaction at different spatial scales: what we know and what we need to know

    Creed, Robert P. (2000)
    The North American weevil (Euhrychiopsis lecontei(Dietz))is being considered as a biological control agent for Eurasianwatermilfoil (Myriophyllum spicatumL.). This native insectdamages watermilfoil plants and is frequently associated withdeclining watermilfoil populations
  • Influence of Sediment Nutrients on Growth of Emergent Hygrophila

    Hanlon, David L.; Dingler, Peter M. (2000)
    Hygrophila (Hygrophilapolysperma(Roxb.) T. Anderson) isa plants which forms serious aquatic weed problems. Bothsubmerged and emergent growth forms occur. Nutritionalstudies with a controlled release fertilizer and sediments collectedfrom hygrophila-infested areas were conducted withthe emergent growth habit to provide insights into growth ofthis introduced plant. Plant dry weights for experimental 16-week culture periods with low average temperatures were associatedwith low amounts of hygrophila biomass as comparedto culture periods with high average temperatures.Hygrophila cultured in sand rooting media with the controlledrelease fertilizer produced as much as 20 times moredry weight than plants cultured in sediments only. First-degreelinear regression statistics showed hygrophila dryweights were highly related to ammonia nitrogen, magnesium,sodium, and pH values in the sediments. These findingsshow the close relationship of the emergent growthhabit of hygrophila to sediment nutrients. Analyses for certainsediment characteristics may provide an indication ofthe potential growth that may be expected for weed infestationsof this plant. Hygrophila grows year round in southFlorida; however, visual observations of canals and other bodiesof water indicate that lower amounts of hygrophila plantsoccur during the cooler months of year than during the summerseason. These findings show the seasonal growth ofemergent hygrophila occurs with biomass dependent onboth sediment nutrients and temperature.
  • Evaluation of macrophyte control in 38 Florida lakes using triploid grass carp

    Hanlon, Sandra G.; Hoyer, Mark V.; Cichra, Charles E.; Canfield, Daniel E. (2000)
    Florida’s large number of shallow lakes, warm climate andlong growing season have contributed to the development ofexcessive growths of aquatic macrophytes that have seriouslyinterfered with many water use activities. The introductionof exotic aquatic macrophyte species such as hydrilla (Hydrillaverticillata) have added significantly to aquatic plant problemsin Florida lakes. The use of grass carp (Ctenopharyngodonidella) can be an effective and economical control for aquaticvegetation such as hydrilla. Early stocking rates (24 to 74grass carp per hectare of lake area) resulted in grass carpconsumption rates that vastly exceeded the growth rates ofthe aquatic plants and often resulted in the total loss of allsubmersed vegetation. This study looked at 38 Florida lakesthat had been stocked with grass carp for 3 to 10 years withstocking rates ranging from < 1 to 59 grass carp per hectareof lake and 1 to 207 grass carp per hectare of vegetation todetermine the long term effects of grass carp on aquatic macrophytecommunities. The median PAC (percent area coverage)value of aquatic macrophytes for the study lakes afterthey were stocked with grass carp was 14% and the medianPVI (percent volume infested) value of aquatic macrophyteswas 2%. Only lakes stocked with less than 25 to 30 fish perhectare of vegetation tended to have higher than medianPAC and PVI values. When grass carp are stocked at levels of> 25 to 30 fish per hectare of vegetation the complete controlof aquatic vegetation can be achieved, with the exception ofa few species of plants that grass carp have extreme difficultyconsuming. If the management goal for a lake is to controlsome of the problem aquatic plants while maintaining asmall population of predominately unpalatable aquaticplants, grass carp can be stocked at approximately 25 to 30fish per hectare of vegetation.
  • Comparison of Experimental Strategies to Control Torpedograss

    Hanlon, Charles G.; Langeland, Ken (2000)
    Studies were conducted to evaluate whether the herbicideimazapyr or a combination of imazapyr and fluridone couldbe used effectively to control torpedograss (Panicum repensL.), an exotic perennial plant that has replaced more than6,000 ha of native vegetation and degraded quality wildlifehabitat in Lake Okeechobee, Florida. Torpedograss was controlledfor more than one year in some areas following a singleaerial treatment using 0.56, 0.84, or 1.12 kg acidequivalents (ae) imazapyr/ha. Combining imazapyr and fluridonedid not increase the level of torpedograss control. Inareas where plant biomass was reduced by fire prior to beingtreated with 0.84 or 1.12 kg ae imazapyr/ha, torpedograsswas controlled for more than two years and native plant species,including duck potato (Sagittaria lancifoliaL.) and pickerelweed(Pontederia cordataL.) became the dominantvegetation in less than one year. Although torpedograss wascontrolled in some areas, little or no long-term control wasobserved at 16 of the 26 treatment locations. To reduce theuncertainty associated with predicting long-term treatmentaffects, additional studies are needed to determine whetherenvironmental factors such as periphyton mats, plant thatch,hydroperiod and water depth affect treatment efficacy., he
  • Estimating above-ground biomass of Melaleuca quinquenervia in Florida, USA

    Van, T.K.; Rayachhetry, M. B.; Center, T. D. (2000)
    One hundred and thirty-eightMelaleuca quinquenervia(Cav.) S. T. Blake (broad-leaved paperbark) trees were harvestedfrom six sites in South Florida to formulate regressionequations for estimating tree above-ground dry weight.
  • Influence of Water Depth on the Rate of Expansion of Giant Cutgrass Populations and Management Implications

    Fox, Alison M.; Haller, William T. (2000)
    Giant cutgrass (Zizaniopsis miliacea(Michx.) Doell. &Asch.), a tall emergent grass native to the southeastern UnitedStates, was studied in Lake Seminole where it formedlarge expanding stands, and Lake Alice where it was confinedto a stable narrow fringe.
  • Monitoring hydrilla using two RAPD procedures and the Nonindigenous Aquatic Species database

    Madeira, Paul T.; Jacono, Collete C.; Van, Thai K. (2000)
    Hydrilla (Hydrilla verticillata(L.f.) Royle), an invasiveaquatic weed, continues to spread to new regions in the UnitedStates. Two biotypes, one a female dioecious and the othermonoecious have been identified. Management of thespread of hydrilla requires understanding the mechanisms ofintroduction and transport, an ability to map and make availableinformation on distribution, and tools to distinguish theknown U.S. biotypes as well as potential new introductions.Review of the literature and discussions with aquatic scientistsand resource managers point to the aquarium and watergarden plant trades as the primary past mechanism for theregional dispersal of hydrilla while local dispersal is primarilycarried out by other mechanisms such as boat traffic, intentionalintroductions, and waterfowl. The NonindigenousAquatic Species (NAS) database is presented as a tool for assembling,geo-referencing, and making available informationon the distribution of hydrilla. A map of the currentrange of dioecious and monoecious hydrilla by drainage ispresented. Four hydrilla samples, taken from three discrete,non-contiguous regions (Pennsylvania, Connecticut, andWashington State) were examined using two RAPD assays.The first, generated using primer Operon G17, and capableof distinguishing the dioecious and monoecious U.S. biotypes,indicated all four samples were of the monoecious biotype.Results of the second assay using the Stoffel fragmentand 5 primers, produced 111 markers, indicated that thesesamples do not represent new foreign introductions. The differencesin the monoecious and dioecious growth habits andmanagement are discussed.
  • Interactions between American pondweed and monoecious hydrilla grown in mixtures

    Spencer, David F.; Ksander, Gregory G. (2000)
    To assess the potential for monoecious hydrilla (Hydrillaverticillata(L.f.) Royle) to invade existing aquatic plant communities,monoecious hydrilla was grown in mixtures withAmerican pondweed (Potamogeton nodosusPoiret). Whengrown with hydrillafrom axillary turions, American pondweedwas a stronger competitor. When grown with hydrillafrom tubers, American pondweed was equally as strong acompetitor as hydrilla.
  • Population response of triploid grass carp to declining levels of hydrilla in the Santee Cooper Reservoirs, South Carolina

    Kirk, James P.; Morrow, James V.; Killgore, K. Jack; Kozlowski, Steven J. De; Preacher, James W. (2000)
    Approximately 768,500 triploid grass carp (CtenopharyngodonidellaValenciennes) were stocked into the Santee Cooperreservoirs, South Carolina between 1989 and 1996 tocontrol hydrilla (Hydrilla verticillata(L.f.) Royle). Hydrillacoverage was reduced from a high of 17,272 ha during 1994to a few ha by 1998. During 1997, 1998 and 1999, at least 98triploid grass carp were collected yearly for population monitoring.Estimates of age, growth, and mortality, as well aspopulation models, were used in the study to monitor triploidgrass carp and predict population trends. Condition declinedfrom that measured during a previous study in 1994.The annual mortality rate was estimated at 28% in 1997, 32%in 1998 and 39% in 1999; however, only the 1999 mortalityrate was significantly different. Few (2 out of 98) of the triploidgrass carp collected during 1999 were older than age 9.We expect increased mortality due to an aging populationand sparse hydrilla coverage. During 1999, we estimated about63,000 triploid grass carp system wide and project less than3,000 fish by 2004, assuming no future, population sizeCtenopharyngodon idella, Hydrilla

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