14 Preventive, Manual, and Mechanical Methods 14.1 INTRODUCTION Preventive, manual, and mechanical methods form a continuum of plant management options. Avoiding aquatic nuisance problems is the most desirable so preventive measures are needed. If new infestations of nuisance plants are found or if only small areas of aquatic plants need to be managed, manual methods may be appropriate. If a nuisance is already large and can’t be managed manually, then mechanized plant removal is an option or can become part of an integrated aquatic plant management program. Contingency planning cannot be overemphasized. To paraphrase Benjamin Franklin — a gram of foresight prevents a metric ton of milfoil. Typically, aquatic plant invasions have been unnoticed or overlooked until they become problematic. Contingency planning for exotic invasions is similar to planning for other natural disasters. The threat is identified and the resources for dealing with it including people, equipment, and finances are known and can be deployed quickly and easily. Barriers to rapid action, such as the need for permits or legislative approval, are taken care of ahead of time. Preventive, manual, and mechanical approaches form part of the armory of techniques available to manage aquatic plants. 14.2 PREVENTIVE APPROACHES Many aquatic plants have large ranges and are spread naturally by birds, wind, and water current (Johnstone et al., 1985). Many exotic and nuisance aquatic plants spread vegetatively. Natural dispersal of whole plants or long-stemmed fragments long distances is unlikely (Johnstone et al., 1985). As examples, whole plants of water hyacinth (Eichornia crassipes) were found in a waste- water treatment pond and waterlettuce (Pistia stratiotes) was found in a stream in northern Wis- consin, during the summer of 2002 (Frank Koshere, Wisconsin Department of Natural Resources (WDNR), personal communication, 2002). It is unlikely that birds, wind, or water current carried these plants all the way from the southern United States where they are common. Human transport, either knowingly or by accident, is the probable explanation. Human activities that transport plants can be grouped into: (1) equipment related dispersal such as attachment of plant fragments onto boats, boat trailers, float-planes, and fishing gear such as nets; (2) plant- or animal-related dispersal where exotic plants are introduced from aquarium discards, fish stocking, or use of aquatic plants as packaging material for fishing bait or packing in nursery stock of ornamental plants such as water lilies; and (3) deliberate dispersal as a means of habitat enhancement or water gardening (see aquascaping in Chapters 5 and 12), scientific transplant experiments, agriculture (e.g., rice seeds), or anti-social behavior (Johnstone et al., 1985). The magnitude of this problem should not be underestimated. Schmitz (1990) reported that at least 22 species of exotic aquatic and wetland plants have been introduced into Florida. Of the 17 species of aquatic plants that Les and Mehrhoff (1999) identified as non-indigenous to southern New England, 13 escaped from cultivation, two were natural dispersal or accidental introductions, and the mode of introduction for two species was uncertain. Even a location as remote as New Copyright © 2005 by Taylor & Francis Zealand is plagued with aquatic nuisances caused by the introduction of the exotics coontail (Ceratophyllum demersum), egeria (Egeria densa), elodea (Elodea canadensis), hydrilla (Hydrilla verticillata), and Lagarosiphon major (Johnstone et al., 1985). 14.2.1 THE PROBABILITIES OF INVASION Johnstone et al. (1985) found that exotic plant distribution was significantly associated with boating and fishing activities in New Zealand. They expressed the probability of a species dispersing from an infested lake to an uncolonized lake in given time period as the product of the frequency of lakes uncolonized by the species, the frequency of the species being transported by interlake boat traffic, the frequency of interlake boat traffic traveling a defined range of interlake distances; and the number of fragments arriving (all species) at all lakes per unit of time. In addition the propagule must be viable when it reaches the lake, it must find suitable habitat for growth, and it must compete with other species to become successfully established. It must then propagate and spread to become invasive. Waters most at risk for invasion are those with suitable habitat found along the pathway of expansion. Lack of success at dispersal, survival, or reproduction prevents a species from expanding its range. Johnstone et al. (1985) also found that the probability of interlake plant dispersal by boats decreased rapidly as the distance between lakes increased and in New Zealand it was extremely small beyond distances of 125 km. Dispersal distances by boats vary by region and are likely longer in North America (although for Wisconsin, Buchan and Padilla (2000) reported that the average distance traveled by recreational boaters was 45 km) but these distances are usually short and are probably unintentional. This type of dispersal is considerably different than the dispersal that concerns Les and Mehrhoff (1999) where plants are intentionally introduced into an area. Intentional introductions can spread plants long distances because of the care given to insure survival. For purposes of unintentional invasions, lakes can be viewed as islands in a sea of unfavorable aquatic plant habitat (i.e., land). To successfully invade a new lake, aquatic plant viability depends upon surviving desiccation as it crosses the land barrier. The degree of desiccation depends on the time out of water and the desiccation rate. For coontail, hydrilla, elodea, egeria, and L. major, survivorship dropped off dramatically with a 75% or greater weight loss (Johnstone et al., 1985). Viability of desiccated fragments was not obvious from visual inspection. After about 50% weight loss, all the leaves on plant fragments die, but the fragment retained the ability to grow from lateral buds (Johnstone et al., 1985). Coontail was the most desiccation resistant followed by L. major, egeria, elodea, and finally hydrilla. Under laboratory conditions, coontail remained viable for up to 35 hours when dried at 20°C and 50% relative humidity (Johnstone et al., 1985). Studies from British Columbia indicate that Eurasian watermilfoil (Myriophyllum spicatum) lost viability in 7 to 9 hours when dried in the shade in still air (Anonymous, 1981). Desiccation rate depends on the time of day; weather conditions; degree of protections from drying factors such as wind, sun, and vehicle speed; and the species. While laboratory studies of survival rates are informative, they may bear little reality to conditions where invasive plants are found in live wells, bilge water, minnow buckets, the bottom of leaky boats, or in moist gobs wrapped around trailer axles (Figure 14.1). Johnstone et al. (1985) suggest that dispersal, rather than habitat type, are responsible for the distribution patterns of exotic aquatic plants, and Cook (1985) concluded that the establishment of introduced aquatic plants was more dependent on human disturbance of the environment than on plant mobility. The species Johnstone et al. (1985) studied are able to occupy a wide range of habitats and they found that lake trophic status and species distribution patterns were unrelated. This may also be typical of other invasive species. However, if resources are limited, it is prudent to first search for invasives in habitats where they are most likely to occur or become a problem. Knowing preferred habitats informs riparian property owners, lake managers, and government officials of the potential for future lake invasions. Copyright © 2005 by Taylor & Francis Using limnological data from over 300 lakes in the United States and southern Canada, Madsen (1998) found that total phosphorus (TP) and Carlson’s Trophic State Index (TSI) were the best predictors of Eurasian water-milfoil dominance in a lake. Lakes with a TP of 20–60 μg/L or a TSI of 45–65 were most at risk of M. spicatum dominance. Crowell et al. (1994) compared total plant biomass and Eurasian water-milfoil biomass to water clarity and sediment character- istics in Lake Minnetonka, Minnesota, as a means of identifying habitat conditions conducive to producing nuisance biomass conditions. Using habitat information as a tool, monitoring and management resources can first be allocated to the lakes or areas of a lake most likely to develop substantial nuisances. Buchan and Padilla (2000) also developed models to predict the likelihood of Eurasian water- milfoil presence in lakes. They found that the most important factors affecting the presence or absence of M. spicatum were those that influenced water quality factors known to impact milfoil growth, rather than factors associated with human activity and dispersal potential. Their models do not consider dispersal probability to the lake so their concluding remark is, “Lakes with the greatest risk of being invaded will be those with the highest likelihood of both providing suitable milfoil habitat and being recipients of the greatest frequency of recreational boat traffic.” An advantage of some of their models is they are based on data that usually exists in publicly available databases so it is inexpensive to collect and use. Using bioindicators as a quick and inexpensive way of determining habitat suitability, Nichols and Buchan (1997) found that Potamogeton illinoensis, P. pectinatus, P. gramineus, and Najas flexilis were native Wisconsin species that commonly occurred with Eurasian watermilfoil. Their presence should indicate lakes with good milfoil habitat. The preferred depth, pH, alkalinity, and conductivity ranges for P. illinoensis and P. pectinatus are very similar to milfoil. Sparganium angustifolium was negatively associated with milfoil and its preferred water chemistries were quite different. It is a good indicator of lakes where Eurasian watermilfoil is not likely to flourish. FIGURE 14.1 Boat and trailer leaving a boat launching area showing exotic plants (mainly Myriophyllum spicatum) “hitch hiking” on trailer parts. All plant material should be removed before launching in a different lake. Copyright © 2005 by Taylor & Francis The U.S. Army Corps of Engineers (USCAOE) is developing a simulation model (CLIMEX) for analyzing species ranges to determine climate compatibility of potential invasion locations with those of the species home range or known distribution (Madsen, 2000a). It is a promising tool to identify potentially problematic plants for prevention efforts and regulatory exclusion. It requires more information on species life histories, growth potential, distributions, and habitat requirements to become fully useable (Madsen, 2000a). However, using preliminary information, Madsen (2000a) assessed the potential for Cabomba caroliniana, E. densa, H. verticillata (monoecious and dioecious biotypes), Hydrocharis morsus-ranae, Ludwigia uruguayensis, Marsilea quadrifolia, Myriophyllum heterophyllum, Najas marina, N. minor, Nymphoides peltata, and Trapa natans to pose realistic nuisance threats to ecosystems in Minnesota, C. caroliniana, H. verticillata (monoecious biotype), N. peltata, M. heterophyllum, H. morsus-ranae, and T. natans showed the highest probability for success in Minnesota. T. natans, M. heterophyllum, H. verticillata, and C. caroliniana were likely to cause the most severe problems if they successfully invaded. Habitat, the time of year a viable plant propagule arrives at a lake, and stored energy in the propagule determine colonization success. Kimbel (1982) found for Eurasian watermilfoil that low propagule (stem fragments in this case) mortality occurred during late summer, in shallow water. Mortality increased during early autumn, in deep water. Substrate type did not affect mortality. Low total nonstructural carbohydrate (TNC) content was linked to increased mortality. 14.2.2 EDUCATION, ENFORCEMENT, AND MONITORING AS P REVENTIVE APPROACHES Preventive approaches delay or negate nuisance species introductions into uninfested lakes. They depend primarily on regulation, education, monitoring, and mechanical barriers. They are not fail- safe. Public cooperation and the full support of lakeshore residents at uninfested locations are essential. Education, monitoring, and enforcement is most cost effective and practical where there are limited access points to uninfested waters because they are most easily monitored. Education usually involves public information campaigns involving pamphlet distribution, use of news media, and warnings posted at infested locations (Figure 14.2). Minnesota state statutes prohibit a person from possessing, importing, purchasing, selling, propagating, transporting, or introducing a prohibited exotic species and prohibit transporting any aquatic macrophyte on a highway (MDNR, 1998). Other states, Canadian provinces, New Zealand, Australia, and probably others have developed or are developing similar legislation (Clayton, 1996). Citations, usually issued by conservation officers, can result from violating regulations. Often, citations are a very effective educational tool. Whether state regulations are enough to tackle a national or global issue of exotic species is questionable. A review of the broader aspects of non- indigenous species, aquatics included, and suggested technologies for preventing and managing problems on a nationwide basis are provided by USOTA (1993). Lake monitoring by trained volunteers, especially at boat launches is another effective preven- tion tool. The Volunteer Monitor (Smagula et al., 2002) reported locations in New Hampshire, Wisconsin, Massachusetts, and Vermont where volunteers discovered exotic aquatic plant invasions in time for swift management action. The web site http://www.invasivespecies.gov provides a lot of information about the vectors and pathways of aquatic plant species invasions. Also included are a variety of educational and monitoring resources. 14.2.3 BARRIERS AND SANITATION Physical barriers can be used to reduce or eliminate free-floating species or floating plant fragments from spreading to downstream locations (Deutsch, 1974; Cooke et al., 1993). The barriers must be Copyright © 2005 by Taylor & Francis constantly maintained and they are usually not 100% effective. With some species, like water hyacinth, the shear mass of plants makes using barriers problematic (Deutsch, 1974). In British Columbia barriers of welded mesh were placed at selected lake outlets and cleaned regularly to prevent the downstream spread of Eurasian watermilfoil. Generally, barriers were effective in reducing the volume of fragments moving downstream, but some fragments were not retained and milfoil became established downstream (Cooke et al., 1993). Removing floating plant rafts at the water intake was the most cost effective means of plant control at New Zealand hydropower stations (Clayton, 1996). Barriers and nets were an efficient means of removing cut aquatic plants that were concentrated by wind and current in Weyauwega and Buffalo Lakes, Wisconsin (Livermore and Koegel, 1979). Log booms were used in Lake Cidra, Puerto Rico to contain floating mats of water hyacinth after they were broken apart and pushed to a take-out point (Smith, 1998). Once captured, the mats were removed with a bucket excavator. FIGURE 14.2 Sign at a boat-launching area warning users that those waters contain exotic species and that it is illegal to place a boat or trailer in navigable water with exotics attached. Copyright © 2005 by Taylor & Francis Removing nuisance plants at boat launch sites is important for preventing species spread from lake to lake. In New Zealand, Johnstone et al. (1985) found that if the area near the boat ramp was plant-free, even if the lake contained nuisance exotics, no plants were found on boats or trailers. 14.3 MANUAL METHODS AND SOFT TECHNOLOGIES Manually pulling or using hand tools such as cutters, rakes, forks, and hooks are the most common mechanical type of aquatic plant management in the world (Madsen, 2000b). It is the method most widely used by lakeshore property owners in the United States. Inexpensive equipment, very selective methods, rapidly deployed techniques, few use restrictions, no foreign substances added to the water, and immediately useable areas are the advantages of manual methods (i.e., soft technologies). However, the methods are labor intensive and hard work. Fatigue often results before management is complete. The areas treated are small and productivity is limited. The methods are usually inexpensive unless labor costs are high. Therefore, manual treatments make good volunteer projects. A local SCUBA club, for example, annually removes Eurasian watermilfoil from Devils Lake, Wisconsin as a service project (Jeff Bode, WDNR personal communication, 2002). The techniques do little environmental harm; mainly because treatment areas are small. There are safety issues while wading or swimming in dense plant beds and when wielding sharp tools, under- water, with limited visibility. Many tools used in manual techniques are available from local hardware or farm supply stores. Some can be found in “junk” piles of outdated farm equipment (McComas 1989). To increase efficacy and efficiency it is important to match the tool to the task (Table 14.1, McComas, 1993). Manual uprooting was used to reduce Eurasian watermilfoil biomass and change plant com- munity structure in high use areas (e.g., swimming beaches) of Chautauqua Lake, New York (Nicholson, 1981a). Two treatments were tested; one where only Eurasian watermilfoil was removed and another where all plants were removed. One year after treatment, milfoil biomass was between 25% and 29% less in the treated areas than in untreated areas. Total plant biomass was between 21% and 29% less (Nicholson, 1981a). Even in the complete removal areas, revegetation was noticeable within a few weeks after treatment. In University Bay of Lake Mendota, Wisconsin, Eurasian watermilfoil was cut as close to the bottom as possible using SCUBA and a sickle or divers knife (Nichols and Cottam, 1972). One FIGURE 14.3 Percentage of constituents by weight (a) and volume (b) of harvested Myriophyllum spicatum. (After Livermore, D.F. and R.G. Koegel. 1979. In: J. Breck, R. Prentki and O. Loucks (Eds.), Aquatic Plants, Lake Management, and Ecosystem Consequences of Lake Harvesting. Inst. Environ. Stud., University Wis- consin, Madison. pp. 307–328.) ( b )( a ) Surface water 44.5% Cellular water 45.5% Air between plants 72.5% 10% solids 1.6% solid 4.3% air within plants 10.7% Surface water 10.9% Cellular water Copyright © 2005 by Taylor & Francis harvest reduced regrowth by at least 50%, two harvests by 75%, and three harvests virtually eliminated plant material during the year of treatment. Harvesting one year reduced the biomass the following year, especially in deep water. Three harvests during the previous year were most effective in controlling biomass the second year. Root removal significantly reduced milfoil biomass in Cayuga Lake, New York 1 year after treatment (Peverly et al., 1974). 14.4 MECHANICAL METHODS 14.4.1 T HE MATERIALS HANDLING PROBLEM Mechanical control of aquatic plants is both a biological and a materials handling problem. Somewhat depressing is the fact that a pile of harvested plants (Eurasian watermilfoil in this case) is approximately 90% water by weight and 75% air by volume (Livermore and Koegel, 1979/ Figure 14.3). A great deal of effort and money is spent on removing and transporting water and air. There are a variety of ways to mechanically remove aquatic plants and every step involves materials handling (Figure 14.4). Understanding and enhancing materials handling increases har- vesting efficiency. It is wise to enlist someone with materials-handling experience (engineer, public works department director) to work with a lake consultant or biologist on a harvesting program. TABLE 14.1 Recommended Manual Methods for Removing Aquatic Plants Based on Rooting Strength a Method Non-Rooted, Free Floating b Weakly Rooted Strongly Rooted Very Strongly Rooted Cutters Straight-edge weed cutter X X X Electric weed cutter X X Scythe, machete, corn knife, diver’s knife, sickle c X- emergent species only X-emergent species only Rakes Garden rake X Modified silage fork X X Landscape rake X X Hand pulling X X X Hay or pulp hook X Drag X X Garden cultivator X Skimmers Modified fish net or seine X a X-rated by McComas (1993) as an excellent or good technique; assumes the user is wading or working from shore, a pier, or boat. b Non-rooted, free floating include free-floating species, plant fragments, and species like Ceratophyllum demersum and Chara sp.; weakly rooted species are plants that can be easily pulled out by the roots like some Potamogeton spp., Elodea spp., and Najas spp.; strongly rooted species are hard to pull by hand, the stems often break before the roots are pulled out, an example is Myriophyllum spicatum; strongly rooted plants are very difficult to uprooted by hand, they are often floating-leaf species like Nymphaea spp. and Nuphar spp. and emergents like Typha spp. and Scirpus spp. Sometimes rooting strength depends on bottom sediments. If in doubt, give a “pull” test. c Recommended for emergents only for safety reasons. Divers knives and sickles are safer when used in conjunction with SCUBA. Copyright © 2005 by Taylor & Francis 14.4.2 MACHINERY AND EQUIPMENT “The diversity of machines devised to cut, shred, crush, suck, or roll aquatic plants would be large enough to fill a museum” (Wade, 1990). Aquatic cutters and harvesters evolved from agricultural equipment. Over the years there have been numerous designs to make machinery more efficient, less costly, safer, more reliable, or to use in special circumstances (Deutsch, 1974; Dauffenbach, 1998). The two basic designs are those with a bow reciprocating cutter or a bow rotary cutter (Livermore and Koegel, 1979). “Sawfish,” “Waterbug,” “Chub,” “Cookie Cutter,” “Sawboat” and “Swamp Devil” were some colorful names given to these machines. Bow rotary cutting machines are used primarily on emergent or floating-leaved plants. They chop plants into small pieces and return them to the water, “blow” them on to the bank, or “blow” them into transport equipment. Bow reciprocating cutters are the industry standard (Figure 14.5). Some machines only cut plants, others are harvesters that elevate cut plant from the water and load them for transport. Sizes range from small, boat mounted cutters to large harvesters with up to 3 m wide cutters that can cut to a 2-m depth, and can transport 30 m 3 of harvested material. A transport barge, shoreline conveyor, a trailer or wheels to transport the harvester on land, and dump trucks are additional equipment often used in a harvesting operation (Figure 14.5). Diver-operated suction dredges, FIGURE 14.4 Flow chart of alternative harvesting options. (From Livermore, D.F. and R.G. Koegel. 1979. In: J. Breck, R. Prentki and O. Loucks (Eds.), Aquatic Plants, Lake Management, and Ecosystem Consequences of Lake Harvesting. Inst. Environ. Stud., University of Wisconsin, Madison, WI. pp. 307–328.) Immediate pickup via conveyor behind cutter bar On-board processing to remove excess moisture and improve handling characteristics Transport on-board to shore removal site Transport floating vegetation in water using current, wind or towing in floating enclosure Pick up from water and transfer to shore at stationary take-out points Transfer to shore Cut plants (in lake) Pick up floating vegetation after horizontal concentration Transfer to utilization site Process to give desired characteristics for intended use Permit cut plants to rise to surface Path 1 Path 2 Path 2a Path 2b Copyright © 2005 by Taylor & Francis machines that use water pressure to “wash” plants out of the bottom, and cultivating and rototilling machines are also used for aquatic plant management. Harvesters are somewhat awkward to maneuver, have a limited cutting depth, and, because of the large conveyor, have a limited forward speed (Figure 14.5). Efforts to overcome these limitations have led to numerous innovations including two stage harvesting where plants are cut in one stage FIGURE 14.5 Mechanical harvester (a) and shoreline unloading equipment (b) operating in Lake Monona, Wisconsin. (a) (b) Copyright © 2005 by Taylor & Francis and removed in a secondary operation (Livermore and Koegel, 1979). Therefore, the distinction cannot always be made between a cutter and a harvester based solely on the machinery used. Harvesting means that the plants are removed from the water but it may not be done in a single operation. There is a continuum of options between cutting and harvesting. 14.4.3 CUTTING Cutting is more rapid than harvesting, the machinery is usually less costly, it may be the most appropriate method for managing annual and emergent species in shallow water, it can be done in deeper water than harvesting, small cutters can operate in areas harvesters can not, and efficiency might be increased by cutting and removing plants in separate operations. However, cutting may spread the aquatic plant nuisance, a secondary operation may be needed to remove plants, and floating plants may become a health, safety, or environmental problem. 14.4.3.1 Case Study: Water chestnut (Trapa natans) Management in New York, Maryland, and Vermont Water chestnut is a floating-leaf aquatic plant introduced into the United States from Eurasia by at least the late 1800s. It is found in the northeastern United States as far south as northern Virginia. Water chestnut is a true annual that over winters entirely by seeds that germinate in late May. By early June a dense canopy of rosettes form on the water surface. Flowering occurs in early July, the first fruits reach maturity in August, and seed production continues until the plant dies in the fall. The seeds sink when released. Water chestnut grows aggressively, lacks food or shelter value to most fish and waterfowl, impedes boat traffic, and its spiny fruits cause painful wounds to swimmers. However, because it is an annual, populations can be controlled if the plant is eliminated before seed set. Because some seeds may remain viable in sediments for at least 12 years (Elser, 1966) a plant infestation will not be eliminated in a single year. The USACOE started cutting water chestnut in the Potomac River in the 1920s and 10 years of annual cutting reduced infestations to very low levels. Tidal currents carried cut plants to salt water where they were apparently killed. Water chestnut was not eliminated but could be maintained by annual hand pulling of plants (Elser, 1966). In 1955 large patches of water chestnut were found in the Bird River, Maryland. After seven seasons of cutting and the use of chemicals (2,4,-D, see Chapter 16) the species appeared to be exterminated and the project was terminated (Elser, 1966). This assessment proved to be premature and several large patches were discovered in 1964 along with patches in the Sassafras River system, Maryland. These areas were harvested but the infestations grew so rapidly they could not be managed by harvesting alone in 1964. In 1965 about 73 ha were harvested and rosettes on the remaining plants turned brown and fell off — possibly from saltwater intrusion (Elser, 1966). No results were reported after 1965 but it is obvious that continued vigilance is needed to manage water chestnut by cutting or chemicals but management efforts can be reduced to low levels once plants are under control (see section on maintenance management in Chapter 16). In Watervliet Reservoir, New York (175 ha, 3.5 m mean depth) water chestnuts were cut 10 cm below the water surface with a sharp, V-shaped metal blade mounted on the front of an air boat (Methe et al., 1993). In an uncut area of the reservoir water-chestnut seeds were recruited to the seed bank while in the cut areas the seed bank declined (Madsen, 1993). Rosettes were not removed after cutting and Methe et al. (1993) found that rosette fragments containing buds or flowers at the time of cutting were capable of producing mature seeds. The cutting experiment at Watervliet Reservoir apparently was not continued long enough to determine whether cutting could eliminate the water-chestnut problem. However, the lesson learned is that cutting early and often is needed to eliminate water chestnut and vigilance is needed for a number of years so an area is not reinfested from a seed bank. Copyright © 2005 by Taylor & Francis [...]... Immediate effects of littoral water chemistry and metabolism Water Res 12: 55–57 Clayton, J.S 1996 Aquatic weeds and their control in New Zealand Lakes Lake and Reservoir Manage 12(4): 477–486 Conyers, D.L and G.D Cooke 1982 A comparison of the costs of harvesting and herbicides and their effectiveness in nutrient removal and control of macrophyte biomass In: J Taggart and L Moore (Eds.), Lake Restoration, ... to the Restoration of Nutrient-enriched Shallow Lakes Broads Authority, Norwich, Norfolk, U.K Neel, J.K., S.A Peterson and W.L Smith 1973 Weed Harvest and Lake Nutrient Dynamics Ecol Res Series, USEPA-660/ 3-7 3-0 01 Newroth, P.R 1980 Case study of aquatic plant management for lake restoration and preservation in British Columbia, In: Anonymous (Ed.), Proceedings of an International Symposium on Restoration. .. Symposium on Restoration of Lakes and Inland Waters USEPA-440/ 5-8 1-0 10 pp 146 –152 Nichols, S.A 1974 Mechanical and Habitat Manipulation for Aquatic Plant Management Tech Bull 77 Wisconsin Dept Nat Res., Madison, WI Nichols, S.A and L Buchan 1997 Use of native macrophytes as indicators of suitable Eurasian watermilfoil habitat in Wisconsin lakes J Aquatic Plant Manage 35: 21–24 Nichols, S.A and G Cottam 1972... objectives were to: (1) provide long-term milfoil control, (2) remove root systems, and (3) permit treatment where no other methods were practical Depending on local FIGURE 14. 9 A diver operated dredge designed by the British Columbia Ministry of Environment, Lands, and Parks (From Cooke, G.D et al 1993 Restoration and Management of Lakes and Reservoirs, 2nd ed Lewis Publishers and CRC Press, Boca Raton, FL... areas of chronic plant problems Non-selective, length of treatment dependent on number of time cut Heavy mats of floating or emergent plants Volume reduction for easier transport of submergent species Non-selective, length of treatment dependent on the timing and number of cuts Slow and expensive, labor intensive Best suited for small areas of moderate density nuisance plants Minimal regrowth of Eurasian... water-milfoil decline of the mid-1970s In assessing the long-term impact of plant management methodologies on Eurasian watermilfoil in southeast Wisconsin, Helsel et al (1999) found that in seven out of nine lakes studied, native aquatic plant species increased or remained the same and in eight out of nine lakes, Eurasian watermilfoil remained the same or declined regardless of the aquatic plant management. .. (Dauffenbach, 1998) This design is most commonly used on free-floating and emergent species and can often work in very shallow water The efficacy of shredding and crushing is not reported but it should be similar to conventional harvesting The major concerns with shredding and crushing are returning viable plant fragments and nutrient-containing and oxygen-demanding materials to the water The changes in water... Peterson and P.R Newroth 1993 Restoration and Management of Lakes and Reservoirs, 2nd ed Lewis Publishers and CRC Press, Boca Raton, FL Copyright © 2005 by Taylor & Francis Crowell, W., N Troelstrup, L Queen and J Perry 1994 Effects of harvesting on plant communities dominated by Eurasian watermilfoil in Lake Minnetonka, MN J Aquatic Plant Manage 32: 56–60 Dauffenbach, G 1998 Part I: Past, present, and. .. Champlain (Vermont-New York) Aquatic Plant Cont Res Prog., Tech Notes, ERDC TN-APCRP-MI-05 U.S Army Corps of Engineers, Vicksburg, MS Johnson, R.E and M.R Bagwell 1979 Effects of mechanical cutting on submersed vegetation in a Louisana lake J Aquatic Plant Manage 17: 54–57 Johnstone, I.M., B.T Coffey and C Howard-Williams 1985 The role of recreational boat traffic in the interlake dispersal of macrophytes:... effectiveness of harvesting in Chemung Lake, Ontario depended upon the time of year of harvesting and the number of harvests per season Harvests in June and July were least effective in lowering the regrowth rate and plant density Two harvests and three harvests per season were most effective in reducing stem number and height (Cooke et al., 1986) The results of multiple hand cuttings of milfoil in . species of exotic aquatic and wetland plants have been introduced into Florida. Of the 17 species of aquatic plants that Les and Mehrhoff (1999) identified as non-indigenous to southern New England,. annual hand pulling of plants (Elser, 1966). In 1955 large patches of water chestnut were found in the Bird River, Maryland. After seven seasons of cutting and the use of chemicals (2,4,-D, see Chapter. the 1 5- and 20-node stage. Volunteers were organized to cut curly-leaf on French, Alimagnet, Diamond, and Weaver lakes, Minnesota in May or early June of 1996, 1997, and 1998 (McComas and Stuckert,