Xft Mk K2 UNIVERSITY OF FLORIDA m Center for Aquatic Weeds AQUAPHYTE International Plant Protection Center AQUATIC WEED PROGRAM VOLUME 2, NUMBER 2 GAINESVILLE, FLORIDA/U.S.A. FALL 1982 MECHANICAL CONTROL OF AQUATIC WEEDS Of the various classes of aquatic plant controls, mechanical control is the most en¬ ergy intensive to implement. Heavy duty machines, some large enough to hold tons of collected plants, use sheer force to push pull, rake, stab, lift, pound, squeeze, throw, haul, bundle, load and carry away tons and tons of vegetable matter. Very high growth densities for aquatic "weeds" mean that one acre of fresh plant mass can weigh 150 tons and more. If a mechanical system could re¬ move an average of two acres of high- density plant mass per hour from an infest¬ ed 400 acre lake, the crew would still be there five weeks later. Consider the thou¬ sands of lakes and untold thousands of miles of rivers and drainage systems which require weed control. For example, accord¬ ing to H. Price (1981), the 5.5 million hect¬ ares of agricultural land in England and Wales is drained by a system of channels, the total length of which is estimated to ex¬ ceed 70,000 km. (In his review of current mechanical controls, Price names several European companies which produce weed cutting and harvesting machines used for waterway and bank weed control.) Mechanical control systems have been the subject of recent studies in North Amer¬ ica and in Europe. Some weed specialists at¬ tribute interest in mechanical control to the heightened public concern about the use of chemical controls and their potential ef¬ fects on aquatic ecosystems. Others do not want to rely on biological controls using exotic species which mav compete with na¬ tive species. Other researchers believe care¬ fully integrating all of these controls has the best chance to reduce explosive plant growth to natural and manageable rates. Manipulation of the environment through integrated control (IPM) is in its infancy and is being examined world-wide. How¬ ever, many severe infestations demand the immediate, tangible results provided by the use of mechanical controls. FIRST LARGE MACHINES The first large experimental machinery used to combat aquatic weeds was design¬ ed and built for the Army Corps of Engi¬ neers in 1900. The mechanical control de¬ vice consisted of a pick-up conveyor and sugar cane crusher mounted on a steam¬ boat. Its job was to clear water hyacinth from the waterways of Louisiana. Accord¬ ing to an article written in 1938 by W.E. Wunderlich (with the New Orleans District of the Corps), this slow and cumbersome machine was abandoned after only two years of operation in favor of the quicker and cheaper method of spraying arsenic on the infested waterways. For 35 years, ar¬ senical solutions were the main control of water hyacinths. Wunderlich wrote, the Continued on page 3 UNIVERSITY OF FLORIDA CENTER FOR AQUATIC WEEDS The Center for Aquatic Weeds of the Uni¬ versity of Florida is the State’s lead agency for developing and coordinating research efforts to control noxious plants. Located in Gainesville, Florida, the Center features offices, laboratories and support facilities from which scientists in several disciplines operate. Botanists, hydrologists, biologists, engineers, chemists, agronomists and en¬ tomologists, as well as scientists from other departments, conduct research under the auspices of the Center. Cooperative research with state and fed¬ eral department is also conducted at the Center. In a Cooperative Agreement with the United States Department of Agricul¬ ture, the Center is: 1) evaluating new compounds for aquatic weed control (Dr. W.T. Haller) 2) evaluating the effects of water and substrate on hydrilla growth (Dr. D.E. Can- field) 3) investigating the interrelationships between periphyton, algae and macro¬ phytes (Dr. L.M. Hodgson) 4) surveying aquatic weeds for viral in¬ fections (Dr. J.R. Edwardson) 5) studying competition among aquatic plants (Dr. D.L. Sutton) Jerome V. Shireman 6) using electrophoresis to determine the identity of bio- and ecotypes of aquatic weeds (Dr. R. Wain) 7) investigating the use of an aquatic grasshopper (Parapoynx spp) for hydrilla control (Dr. D. Habeck). Among on-going Center research is that conducted by Dr. Jerome V. Shireman, fish biologist, and his associates, R. Rottmann and R. Aldridge. Shireman is particularly recognized for his work on the grass carp, Ctenopharyngodon idella, and the hybrid cross between the grass carp and the big- head carp. At the Center’s Fish Culture Laboratory, (a complex of buildings, tanks and ponds) Shireman, Rottmann and Al¬ dridge are investigating methods for the artificial spawning and culturing of the hy¬ brids in large numbers. The sterile hybrids have the potential for controlling hydrilla and other problem water plants. Because the hybrids are sterile, there is little chance of tbeir reproductive competition with native fish. Dr. William T. Haller, Acting Director Center for Aquatic Weeds, 8001 N.W. 71st Street, Gainesville, Florida 32606/USA PAGE 2 AQUAPHYTE FALL 1982 FRESHWATER BIOLOGICAL ASSOCIATION The Freshwater Biological Association, grant-aided by the Natural Environment Research Council, is the principal British institute researching the biology of fresh- waters. The FBA has about 2,000 members. It operates two laboratories, a field unit and a technical library which provide re¬ search facilities for its own 120 staff mem¬ bers and a few visiting workers. Labora¬ tories are the Windermere Laboratory, The Ferry House, Ambleside, Cumbria LA22 OLP, and the River Laboratory, East Stoke, Wareham, Dorset BH20 6BB, United King¬ dom. The FBA supports research groups in the following areas: Chemistry, Physics, Microbiology, Protozoology, Mycology, Al¬ gology, Palaeolimnology, Macrophytes, Invertebrates, Fish, Statistics, Electronics, Library and Information Services, as well as the Finance and laboratory staffs. Mac¬ rophyte studies are conducted under the direction of F.H. Dawson and D.F. Westlake. The FBA has published more than 1500 papers by members of its staff and associ¬ ated researchers since its founding in 1929. A monthly library list is also produced for staff and others. According to Miss J.V. Bird, Information Scientist, tbe FBA library staff scans books and journals for items in the field of fresh¬ water studies and classifies the items by sub¬ ject. Among the subjects is "higher plants" which includes about 300 aquatic plant citations per year. The citations are compiled into a list divided into subject sections at the end of each month. At the end of each year the lists are accumulated and produced as separate main subject sections. Annual membership is open to interested parties for ten pounas. Membership infor¬ mation can be obtained from E.D. LeCren, Director of the Association at the Wind¬ ermere Laboratory. Library list information and subscription rates can be obtained from J.E.M. Horne, Librarian, also at the Wind¬ ermere Laboratory. Officers of the Freshwater Biological Association (April 1982) are as follows: President, Sir Edwin Arrowsmith; Chair¬ man of Council, Professor G.E. Fogg; Hon. Treasurer, K.F. Roberts; Chairman, Scientif¬ ic Advisory Committee, Professor W.D.P. Stewart. SALVINIA - POSSIBLE BIOLOGICAL EFFECTS ON FISH IN PAPUA NEW GUINEA? By David Coates, Senior Biologist, Fisheries Research and Survey Branch, Department of Primary Industry, Box 417, Konedobu, Papua New Guinea. Salvirtia moiesta was accidentally or in¬ tentionally introduced into the Sepik River System of Papua New Guinea in the early 1970s. The problems caused by the weed infestation were described in 1980 by Mitchell, Petr and Viner. The Sepik is a huge floodplain river that drains most of the northern part of P.N.G. Very little scientific work has ever been done on the river. In the lower reaches of the floodplain are numerous ox-bow lakes, formed as the river meandered and changed its course, and a small number of depression lakes. Salvinia predom¬ inates in these lotic (still) waters. The weed is reported to have caused many problems but most have yet to be quantified. In 1980 a programme of control was ini¬ tiated. It is led by Mr. P.A. Thomas, De¬ partment of Primary Industry, BMS, We- wak, P.N.G. In addition, Fisheries Research and Surveys Branch of the Department of Primary Industry are directly concerned with the effects of the weed on the fish and Mitchell, D.S.; T. Petr; A.B. Viner. 1980. The water-fern Salvinia moiesta in the Sepik River, Papua New Guinea. Environmental Conservation 7:115-122. fisheries of the area. The weed does inter¬ fere with river transport and the setting of nets but it is not clear to what extent. The weed has also been blamed for the decline of the local salted fish industry, based on Tilapia (Oreochromis mossambicus), but any attempts to relate this decline with an increase in Salvinia are conjectural. Research has been undertaken to try to find out exactly what effect the weed has. Full results will be presented shortly. Salvinia does have its usual effect of lowering in-water primary production in permanently infested areas resulting in a reduction in oxygen levels. Benthic fauna is usually obliterated under permanent mats. However, as usual, Salvinia has a consider¬ able in-fauna associated with the plant it¬ self. In the Sepik, Salvinia represents a considerable increase in available fish food (invertebrate fauna) in areas (ox-bows) which anyway are very low in abundance of natural food. Extensive gili-net surveys have been undertaken. There appears to be little difference in catch rates between heavily infested and clear areas. At present the weed is thought to have had little effect on the fish production of the area. The main reason for this is that the weed is usually restricted to areas with naturally low pro¬ ductivity. For example, T.A. Redding- Coates has been studying the biology of Sepik tilapia. It is thought that the majority of fish production occurs on the floodplain during the flood. Salvinia does not norm¬ ally predominate in this environment. However, the situation is certainly com¬ plex and efforts are hampered by an almost complete lack of previous research in the area. The Aquatic Weed Program database has proved invaluable in obtaining references to similar or related work but it is clear that much more is known about the effects of fish on weeds than the effects of weeds on fish! We would certainly like to hear from anybody who has worked on similar prob¬ lems. AQUATICS Magazine is an informative, four-color quarterly magazine, the official publication of the Florida Aquatic Plant Management Society. It features articles on aquatic plants and their control, particularly in Florida. Special features deal with tech¬ niques of controls, new developments from industry, articles from regulatory agencies, discussions of legislative and administrative actions which affect aquatic weed control and progress reports from the resarch com¬ munity. AQUATICS is edited by Paul C. Myers. Membership/subscriptions cost only $5.00 (U.S.) per year. According to Myers, orders should be sent to Mr. Jim McGehee, Treasurer, Florida Aquatic Plant Manage¬ ment Society, P.O. Box 212, Maclenny, Flor¬ ida 32063. In addition to other news items and announcements, the June, 1982 issue of AQUATICS features the following articles: 1) The Watermilfoils of Florida by Anita Tiller. A review of the six Myriophyllum species now found in Florida. 2) Hydrilla - Miracle or Migraine for Florida’s Sportfish by Douglas E. Colie. Documents three sportfish populations in the presence of hydrilla. 3) The Waterhyacinth Weevils by Ted D. Center. Reviews the taxonomy and identi¬ fication, the biology and life bistories, the pathological effects and population con¬ servation of these biological controls. 4) Herbicides vs. Grass Carp by John A. Osborne. Compares the short- and long¬ term economics of two hydrilla controls. L 0 1 - UNIVERSITY OF FLORIDA - Center for Aquatic Weeds //ihi AQUAPHYTE Mi International Plant Protection Center '<])/ (( - — AQUATIC WEED PROGRAM - SI MBER 2 GAINESVILLE. FLORIDA I S A FALL 1MZ Newsletter of the Center for Aquatic Weeds and the IPPC Aquatic Weed Program of the University of Florida. The Center for Aquatic Weeds is in the Institute of Food and Agri¬ cultural Sciences (IFASj. The International Plant Protection Center (IPPC] is a unit of Oregon State University and is funded by the United States Agency for International De¬ velopment. Editor: Victor Ramey AQUAPHYTE is distributed to three thousand aquatic biologists and agen¬ cies world-wide. Comments, announce¬ ments, news items and other informa¬ tion relevant to aquatic plant research are solicited. We gladly permit free republication of AQUAPHYTE items when accompanied by full acknowledgement. Views and interpreta¬ tions in this publication are not attributable to the U.S. Agency for International Develop¬ ment nor any individual acting in their behalf. Inclusion in AQUAPHYTE does not consti¬ tute enforsement, nor should exclusion be interpreted as criticism of any item, firm or institution by IPPC, the University of Florida or AID. FALL 1982 AQUAPHYTE PAGE 3 MECHANICAL CONTROL OF AQUATIC PLANTS Continued from page 1 "deadly poison" was a "hazard to the oper¬ ating personnel of the sprayboat, the resid¬ ents living along the streams which were sprayed, and animal life in general ... the loss of livestock from time to time and the physical inconveniences experienced by the personnel of the sprayboat only served to emphasize the necessity for some effective means of combating this aquatic growth which would not entail the use of poisonous materials." According to Wunderlich, nei¬ ther did arsenic have effect on a newly ar¬ rived aquatic weed, alligatorweed (Alter- manthera philoxeroides). So, after 35 years, the Corps of Engineers was again authorized to conduct the neces¬ sary tests to design a machine for the con¬ trol of aquatic weeds. The result was the construction in 1937 of the "Kenny", a motorized steel barge fit¬ ted with a conveyor which scooped up the hyacinth and conveyed the plants to on¬ board machinery which crushed the plants. The mangled hyacinths were then washed overboard to decompose in the water. The 80 X 24 foot barge employed a crew of five. Several other workers were employed in the raking and feeding of plants to the barge. According to Wunderlich, the Kenny was operated around the clock and had a capacity of more than 200 acres of surface vegetation per month. A detailed descrip¬ tion of the Kenny is found in The Military Engineer 30:5-10 (1938). Wunderlich con¬ cluded, "Mechanical destruction machines of this type ... will prove to be entirely satis¬ factory ... and will definitely supplant the older and more hazardous method of de¬ struction by spraying with poison." Between 1937 and 1950 the development and use of smaller boats ("saw boats") for the clearance of canals and small rivers in¬ creased. Submerged blades cut the plants and left them to decompose in the water. With the advent of a new generation of chemical controls such as 2, 4-D, the Kenny was retired in 1951. These chemicals and the improved techniques for their safer use began to replace mechanical devices. In another article in 1967, Wunderlich re¬ viewed the history of mechanical controls and concluded, "It would appear that a well planned combined mechanical/chemical approach is the most satisfactory method of keeping our waterways open at a reason¬ able cost ... caution is advised against the mistaken belief that either chemicals or machinery will produce a one-time cleanup operation that can be walked away from and forgotten." MODERN MACHINES Several mechanical control systems and sizes are now manufactured. However, none can perform all of the tasks necessary to control all problem species. Most devices which are suitable for canal maintenance are too small for large river or lake mainte¬ nance. Systems which only cut below the water cannot be used to collect floating plants. A system which cuts to a maximum depth of 2.5 feet may not effectively control plants which grow in water deeper than 2.5 feet. Some aquatic plants reach several feet above the surface of the water, while others form thick mats on the surface requiring a multiplicity of machine capabilities. Most harvesting operations require at least the cutting, collecting and loading, transporting to shore, unloading and then conveying to other locations for the de¬ composition and/or utilization of the nui¬ sance plants. Because the bulk of plants such as water hyacinth is so great, on¬ board processing of the plant to reduce its mass is sometimes an additional operation. Effectiveness of mechanical systems is measured in terms of acres per hour har¬ vested and/or average tons per hour harvest¬ ed. Biomass per acre varies substantially be¬ tween target species: hydrilla, 20 tons/acre; water hyacinth, 150 tons/ acre; and water- milfoil two tons/acre. Nutrient availability, temperature, time of year and other conditions can cause wide var¬ iation in the biomass data of a single species. A system might perform with twice the effi¬ ciency on one species than on another. And, of course, weather conditions, water velo¬ city and the condition of the system and crew all contribute to the system’s efficien¬ cy. "Downtime" for maintenance and repair is also figured into a system’s efficiency. Some systems show a 25% downtime under field conditions, possibly raising the sys¬ tem's real cost to unacceptable levels. Questions as to the desire for small or large area control must be considered in choosing systems. Other basic questions to consider might be: can the system outstrip the growth of the weed, will the harvest have retardant effects on the re-establish¬ ment and growth of the target plant, will harvesting reduce the nutrient load of the water column, and does the actual problem justify the actual financial and environ¬ mental costs of mechanical control. The U.S. Army Corps of Engineers con¬ siders a system which can harvest and dis¬ pose of 80 to 100 tons/hr to be efficient enough to control the known growth rates of water hyacinth and hydrilla (M.M. Culpepper; J.L. Decell. 1978. Mechanical harvesting of aquatic plants. Tech. Rep. A- 78-3. Rep.l V.l). In 1975, the Jacksonville district of the Army Corps requested a thorough evaluation of the most advanced off-the-shelf large-scale mechanical control system. According to the report, "local opposition to the use of chemicals to control water hyacinths and the lack of a federally registered chemical to control hydrilla" prompted the request. Consequently, the Corps' Waterways Ex¬ periment Station in Vicksburg, Mississippi chose the three part system known as the Aqua-Trio (manufactured by Aquamarine Corporation) for detailed operational tests. After tests under many conditions, their major findings were that even the most ad¬ vanced off-the-shelf system does not meet the Corps' fundamental efficiency require¬ ment to be able to harvest and dispose of 80 to 100 tons/hr." Among their conclusions: (a): total Aqua-Trio system productivity was less than 10 tons/hr with the pacing component being the transport in water hyacinth and the harvester in hydrilla; (b) of the three components of the Aqua-Trio, only the onshore conveyor had production rates that demonstrated a potential for reaching 80 tons/hr; the other components involved excessive mechanical handling of the plants; and (c) transporting the har¬ vested material over water appeared to be the major pacing problem in developing a high-production mechanical harvesting system." The two-volume report by Culpepper and Decell includes detailed time charts of tasks performed by each component of this system. The Army Corps' "first totally operation¬ al test of a mechanical system for hydrilla control" was conducted by J.T. McGehee in 1977. Using an Aqua-Trio System, 65 hectares of Orange Lake, Florida were maintained during June-October. During this period, 1100 loads of hydrilla were cut and disposed of in the water and on land. Total control costs per hectare for the peri¬ od was approximately $1,125.00. One of McGehee's conclusions, "Trails for naviga¬ tion from access points in the lake to natural open water fishing areas and cut fishing areas were maintained useably free of hy¬ drilla at a cost that was competitive with chemical methods of control." In another Corps test (1980), I1. A. Smith reported the mechanical removal efficiency of water hyacinths and hydrilla in two Florida locations. In the riverine test, the system harvested an average 1.94 acre/hr, but demonstrated peak production rates in excess of 2.3 acre/hr (approximately 18 tons/hr). This 121 page report also reviews many problems of mechanical control sys¬ tems in general and makes recommenda¬ tions as to appropriate areas of systems re¬ search and development. Smith concluded that the major limiting component for mechanical systems was not their cutting but their conveying components: "No com¬ plete conveying system exists that ade¬ quately fulfills the requirements of remov¬ ing plants from on- water storage areas. The major problem with conveying is maintain¬ ing the proper feed of plants to the convey¬ or." In a second part of this study, Smith collected data on the on-shore decomposi- ton of harvested hydrilla and water hya¬ cinths. In test hydrilla stockpiles, only 17 percent of the original volume remained af¬ ter 30 days. J.L. Smith performed hydrilla control tests in 1979-80 using the Limnos Harvest¬ er. This system cuts and collects plants and moves them to an on-board hammermill where the harvested hydrilla is chopped in¬ to quarter-inch fragments. The plant frag¬ ment/slurry is pumped to barges for trans¬ portation to on-shore disposal sites. Based on numerous tests in the Withlacoochee River and Orange Lake (Florida), the cutter by itself averaged 4.26 acres/hr. When the hammermill and barge components were figured into the system, the overall har¬ vesting average was 1.79 acres/hr. Smith recommends specific improvements to in¬ crease harvesting productivity. Test results of the Aquamarine highball- er and H-650 Harvester were reported by L. J. Touzeau of the Florida Game and Fresh¬ water Commission in 1972. Tests were con¬ ducted on the wide St. John's river (Flor¬ ida). The Milfoil Harvesting Program Report (1982), prepared by METRO, Seattle, Washington, reports this city's mechanical control program of Myriophyllum spica- tum. It details their experiences with two MUDCAT harvesters over a two-year period in several Seattle area lakes. Re¬ cords of costs incurred (machines, person¬ nel, hours, repairs, etc.), problems and suc¬ cesses are presented. Data on acres har¬ vested and cubic yards handled are includ¬ ed in graph form. ContinuecJ on page 4 PAGE 4 AQUAPHYTE FALL 1982 MECHANICAL CONTROL OF AQUATIC PLANTS Continued from page 3 Results of operational tests of a variety of mechanical weed control devices on Myrio- phyllum spicatum was reported by G.D. Armour in 1980. His is one of many reports by the government of British Columbia on controls of watermilfoil. In their attempt to eradicate watermilfoil from their lakes, nine devices were used and evaluated. Technical design specifications and operat¬ ing statistics for rotavators, H-650 harvest¬ ers, a diving system, a dredge, fragment containment booms and a diver dredge are presented. REVIEWS The most recent review (Nov. 1981) of off-the-shelf mechanical control systems is by G.Canellos of the MITRE Corporation. An exhaustive review of the literature, this report features a section on the current status of dredging, cutting and harvesting equipment. Technical specifications and costs of several systems, as well as user re¬ sults, are presented in this 140-page report. Other reports include S.A. Nichols’ sur¬ vey of harvesting experiences in Wisconsin before 1974 and A.V. Kozloff's (1973) com¬ parison between chemical and mechanical controls. Because chemically treated plants are left to decompose in the water, adding to the lake's fertility, Kozloff concluded, "Harvesting is the only current method that solves the problems of excessive nutrient content in a body of water." A catalogue of surface-operating aquatic weed equipment was compiled by A.E. Deutsch and published in 1974 by IPPC- Oregon State University. Aquatic weed cutters, rakes, harvesters and barriers built by twelve companies were described. HARVESTING EFFECTS The Aquatic Weed Database has few re¬ ports of the short- and long-term effects of mechanical controls on the ecosystem or on regrowth of the target plant. A conference at the University of Wis¬ consin in 1979 did address the effects of harvesting. The Proceedings of the Aquatic Plants, Lake Managment, and Ecosystem Consequences of Lake Harvesting Confer¬ ence, edited by J.E. Breck, R.T. Prentki and O.L. Loucks includes 27 papers divided into sections titled macrophyte biology, nut¬ rient loading and flux of phosphorus from sediment, effects of harvesting on the con¬ sumer community, mechanical harvesting options, institutional settings and an over¬ view. Most of the papers have to do with Myriophyllum spicatum. Short-term effectiveness of a multiple cut strategy and the seasonal variation in carbohydrate translocation and accumula¬ tion in M. spicatum were evaluated by Perkins and Sytsma (1981) to determine long-term biomass reductions and changes in community composition following har¬ vest operations of watermilfoil. Among their conclusions : "Harvesting had a very definite impact upon carbohydrate ac¬ cumulation by eurasian watermilfoil and, if we assume that reserve carbohydrates are significant in terms of overwinter survival and subsequent spring growth flush, proper timing of the harvest may lead to substantial long-term reductions in biomass ... Tentatively, a multiple cut harvesting program would seem necessary in order to provide short term reduction in aquatic plant biomass with a mandatory late season cutting if longer term benefits are desired." ).C. Kimbel and S.R. Carpenter (1981), in a study of the non-structural carbohydrate content and extent of regrowth of M. spica¬ tum in harvested and control plots con¬ cluded: "Harvesting, even once per grow¬ ing season, can reduce Myriophyllum spi¬ catum growth" in following seasons. L.C. Collett, A.J. Collins, P.J. Gibbs and R.J. West in 1981 reported on the dredging control of Zostera and Ruppia in New South Wales: "All species of macrophytes had re-established in the shallowest (1.0M) plot withing four months but had failed to colonize the deeper plots up to twelve months after dredging. Recolonization of dredged plots by most of the 63 zoobenthic species present in control plots had occured within eight months of treatment." S.R. Carpenter and M.S. Adams of the University of Wisconsin's Center for Biotic Systems reported (1977) the environmental impacts of mechanical harvesting of sub¬ mersed vascular plants. Immediate and long-term effects of harvesting on the phys¬ ical and chemical aspects of lakes and ef¬ fects on the biota and ecosystmes of lakes are proposed. Among their conclusions: "Although current information on macro¬ phyte harvesting is limited, harvesting of¬ fers unique opportunities for experimental manipulation of lake ecosystems. As a management tool, harvesting appears to of¬ fer a good deal of unexplored potential al¬ though its environmental impacts are not well-known." B. Sabol wrote in 1980, "If barging could be eliminated as a necessary step in harvest¬ ing operations, operational cost could be cut by up to 50 percent." In a later report to the 16th Annual APCRP meeting (1981), Sabol reported on the predicted and actual results of aquatic disposal of chopped hy- drilla in Orange Lake, Florida. He reported the "lack of a detectable oxygen sag," no problem algal bloom, and very little hy- drilla fragment regrowth in the lake dispo¬ sal test. However, in a 1978 report discussing the acceptability of disposing of weed slurry directly into New Zealand lake water, B.T. Coffey, G.W. Coulter, and J.S. Clayton wrote, "The case against disposal of har¬ vested weed in wateris sufficiently clear to be accepted as a principle where further en¬ richment of a water body is not desired." COMPUTER MODELS Mathematical and computer models of control technologies and their effects help users and engineers in the development of more efficient systems. A computer simu¬ lation model was described by E.R. Perrier and A.C. Gibson in 1982. This updated ver¬ sion of the Winfrey Model (developed by Dr. Sam Winfrey) is entitled "Simulation for Harvesting of Aquatic Plants (SHAP)". The publication is actually a manual for the use of the SHAP program. SHAP requires no prior computer programming experience for its use. Another mathematical model was used by M.]. Mara in predicting the annual costs of mechanical control of water hyacinths on a 400 acre lake under specified condi¬ tions to be $13,500 or $33. 75/acre in 1976. Mara suggests: "The high cost of mechani¬ cal harvesting in comparison to the cost of chemical control suggests that a combina¬ tion of mechanical and chemical methods may be optimal from society’s point of view. Mechanical methods could be used to rid the water body of most of the infestation. Hya¬ cinths remaining could then be spot sprayed with chemicals to further cut the infestation." J.H. Neil of Limnos Ltd. (1979) used a computer model "to predict the overall cap acity of the harvesting system for a specific set of (up to 14) conditions." The model was applied to a test of the Limnos Harvester, but, according to Neil, the model can be ap¬ plied to other mechanical equipment as well. T.D. Hutto (1981) discussed computer models which aid in the evaluation and de¬ sign of existing and proposed mechanical harvesting systems. He particularly de¬ scribed HARVEST, a first-generation com¬ puter model being developed by the Army Corps Waterways Experiment Station in Vicksburg, Mississippi. He presented per¬ formance predictions tor two equipment mixes for each of three existing mechanical control systems. According to Hutto, the predictive model can be applied to several makes and models of harvesting systems. The Aquatic Weed Database has 450 arti¬ cles catalogued under the catagory "Mech¬ anical control". Selected articles, including those cited above, are listed on page 6. The manufacturers: Air-Lec Industries, Inc., 3300 Commercial Avenue, Madison, Wisconsin 53714/USA (608) 244-4754 Allied Aquatics International, Inc., 5029 Flournoy Lucas Road, Shreveport, Louis¬ iana 77129/USA (318) 688-0545 Aquamarine Corporation, Box 616, Wau¬ kesha, Wisconsin 53186/USA (414) 547-0211 Aztec Development Company, P.O. Box 3348, Orlando, Florida 32802/USA (305) 849- 6420 Hockney Company, 913 Cogswell Drive, Silver Lake, Wisconsin 53170/USA (414) 889-4581 Lantana Boatyards, Inc., 808 N. Dixie High¬ way, Lantana, Florida 33462/USA (305) 585- 9311 Limnos Ltd., 22 Roe Avenue, Toronto, On¬ tario, CANADA (416) 487-8874 Mudcat Division, National Car Rental Company, P.O. Box 16247, St. Louis Park, Minnesota 55416/USA (612) 893-6400 Rolba Limited, Charlwoods Road, East Grinstead, East Sussex RH19 2HU, ENG¬ LAND John Wilder Engineering Ltd., Hithercroft Works, Wollingford, Oxon, 0X10 9 AR, ENGLAND. FALL 1982 AQUAPHYTE PAGE 5 HOCKNEY Hockney produces an underwater bar weed cutter barge. The HC-10 has a cutller width of 10 feet and can operate down to 5 feet. The HP-7 is a bar-type portable cutter which can be purchased separately and mounted on small boats. Its cutter width is 7 feet and it can operate to depths of 4 feet. LIMNOS This company pro¬ duces an aquatic weed harvesting system. The system consists of a cut¬ ter, a harvester and two barges. The cutter can clean an 18 foot path to depths of 8 feet. The cut plants are harvested and sent to an on-board grinder which can produce 30 tons/hour ot plant slurry. The slurry is transported to shore in 15-ton capacity barges which then pump it to waiting tanker trucks for disposal. JOHN WILDER ENGINEERING The WATER WARRIOR has a twelve foot cutter bar which can work to a maximum depth of 5’6". It also features a moveable paddle propulsion system and a twelve foot weed rake. AZTEC This company produces the WATER VAC and the WATER WEEDER. The WATER VAC is a system which can dredge plants and hydrosoil in an 8 foot swath to a depth of 15 feet 6 inches. It can penetrate one foot into the hydrosoft remov¬ ing rooted plants and muck and pump or airhlast the dredged material to shore. The WATER WEEDER collects floating or rooted plants, grinds them and then air-blasts the slurry up to 125 feet away. It has a working width of 12 feet and can work to a depth of 13 MUDCAT This company offers several models of cutters, harvesters and shore conveyors. The top-of-the-line model cuts a path 11 feet wide and works to depths of over 6 feet. ALLIED AQUATICS INTERNATL. Allied produces the WATER BUG cutter and the ALPHA I harvester. The WATER BUG cuts a 12 foot path to a depth of 4 feet. The ALPHA I has a harvesting width of 15 feet and an 18-ton capacity. ROLBA LIMITED Rolba does not manufacture weed cutting equipment but acts as agent for Aquamarine and Gibeaux. The Rolba-Gibeaux weed cutting boat features a T- shaped cutting attachment that has a cutting width of 2.34 M and operates to a maximum depth of 1.15M. LANTANA The COOKIE CUTTER is a barge with two circular rotating cutter blades 5 feet in diameter attached to the front. It is used mainly for trail, channel and canal maintenance. It clears a path 8 feet wide and can work down to 3 feet. The COOKIE CUT¬ TER is propelled by the action of the rotat¬ ing blades. AIR-LEC Air-Lee manufactures cutter and rake at¬ tachments for small boats. The cutter has a width of 42 inches and can operate to depths of 42 inches. The weed i rake attachment rakes a path eight fee. wide. AQUAMARINE This company produces several machines for aquatic weed control: 1) SAWFISH - A cutting machine which cuts a swath 8 feet wide to a maximum depth of 3.5 feet. 3) HARVESTERS - With a harvesting width of 8 feet, it can work to 5 feet below the water sur¬ face and can store up to 650 cu/ft or 10,000 lbs of weeds. 4) HYBALLER - For canals and rivers, this machine picks up hyacinth, chops it up and throws it 120 feet to shore. 5) AQUA-TRIO - This harvesting system ;atures a cutter/harvester, a large trans- ort unit and a shore conveyor. 2) CHUB - A cutter- harvester utility boat which cuts 4 feet wide and works to a maximum depth of 5 feet. Its deck can store up to 200 cu/ft or 1500 lbs. of weeds. PAGE 6 AQUAPHYTE FALL 1982 Abd El Sayed. J.K.; A. Tolba; A.H. Druijff. 1978. Evaluation of some machines for mechanical control of aquatic weeds in Egypt. Proc. European Weed Res. Soc. Symp. Aquatic Weeds. 5:359-67. Armour, G.D.; R.S. Hanna; I.P. Walters; M.D. Maxnuk. 1980. Studies on aquatic macrophytes. Part XIV. Summary of mech¬ anical aquatic plant management, Okanagan Valley, 1978. Province of British Columbia, Ministry of Environment, Inven¬ tory and Engineering Branch. 36 pp. Bagnall, L.O. 1980. Intermediate technology screw presses for dewatering aquatic plants. American Soc. Agricultural Engineers Paper No. 80-5044. 14pp. Bagnall, L.O. 1981. Aquatic plant harvesting and harvesters. American Soc. Agricultural Engineers Paper No. 81-5019. 6pp. Baitsch, B. 1967. Possibilities and limitations of mechanical ditch cleaning. Erbeg. Ewrc Intern. Symp. Wasserpflanzen. 2:12-21. W.D. 1965. A study of turbidities caused by re-dredging the intracoastal waterway in Currituck Sound, North Carolina. Mimeographed. Spec. Rept., Dingell-Johnson Proj. F-16-R-1. 6pp. Bakker, J.P. 1978. Changes in a salt-marsh vegetation as a result of grazing and mowing - a five-year studv of permanent plots. Veg- etatio. 38(2):77-87. Behari, R.; N.K. Behl; S. Ram. 1972. Investigations on time of cutting under water and length of submergence of cut stUbbles of Typha latifolia. Second Ann. Rept. (1970-71). Agr. Univ. India, Haryana p. 101. Bernatowicz, S. 1965. Effects of mowing on the occurrence of macrophytes in the Dgalmaly Lake. Acta Hydrobiol. 7(1 ):7 1-82. Beule, J.D. 1979. Control and management of cattails in S.E. Wisconsin Wetlands. Technical Bulletin Department of Natural Resources, Wisconsin. 112:40pp. Bhattacharya, A.P.; S.V. Singh. 1973. Studies on aquatic weed control in irrigation channels in Uttar Pradesh by chem¬ ical and mechanical control. In: Regional Seminar on Noxious Aquatic Vegetation in Tropics and Sub-Tropics, Abstracts. New Delhi, India: UNESCO, 70pp. pp. 33-34. Biology Branch Division of Laboratories. 1972. Kawartha lakes water management study-ecological philosophy of aquatic weed harvesting. Biology Branch Divisiorl of Lab. Ontario Water Resources Commission. 7pp. Blanchard, J.L. 1970. Mechanical and herbicidal lake weed management. Hyacinth Contr. J. 8(2):36-37. Brooker. M.P.; J.H. Baird. 1974. Cost evaluation of water¬ course management in Essex. Surveyor. 16:34-37. Brown, A.H. 1948. The control of water hyacinths by mech¬ anical means. Proc. Soil Sci. Soc. of Fla., 9:66-74. Bruhn, H.D.; D.F. Livermore, F.O. Aboaba. 1971. Processing characteristics of macrophytes as related to mechanical har¬ vesting. Trans. Am. Soc. Agr. Engrs., 14:1004-8. Bruhn, H.E.; et al. 1974. Processing of aquatic vegetation as an aid to mechanical control in irrigation and drainage chan¬ nels. September 1974. Commission Internationale du Genie Rural, VUIth International Congress of Agricultural Engin¬ eering, Tlevohof, The Netherlands. Bryan, A.D. 1978. Experimental hydraulic dredging for aquatic weed control in Vernon Arm Okanagan Lake 1975. Part VIII. Studies on Aquatic Macrophytes. Province of British Columbia, Ministry of the Environment. Inventory and Engin¬ eering Branch. 158pp. Bryant, C.B. 1974. Aquatic weed harvesting costs and equi- ment - 1972. Hyacinth Contr. J. 12:53-55. Bryant, C.B. 1973. Control of aquatic weeds by mechanical harvesting. Pest Articles and News Summaries. 19(4):601-606. Burton, T.M.; D.L. King; J.L. Ervin. 1978. Aquatic plant har¬ vesting as a restoration technique. Lake restoration - Proc. of a Natl. Conf. Aug., 1 State of the Art Research, pp. 177-185. Canellos, G. 1981. Aquatic plants and mechanical methods for their control. The Mitre Corporation, Metrek Division, McLean VA. MTR-81W55. 140pp. Carpenter, S.R.; M.S. Adams. 1977. Environmental impacts of mechanical harvesting of submersed vascular plants. Mad¬ ison, WI: Univ. Wisconsin Center for Biotic Systems. IES Rept. 77. 30pp. Carpenter, S.R.; A. Gasith. 1978. Mechanical cutting of sub¬ mersed macrophytes: immediate effects on littoral waterchem- istry and metabolism. Water Res. 12:55-57. Coffey, B.T.; G.W. Coulter; J.S. Clayton. 1978. Report of working party on waterplant harvesting for officials commit¬ tee on eutrophication. March 1978. Hamilton, New Zealand: Officials Committee on Eutrophication. 13pp. Collett, L.C.; A.J. Collins; P.J. Gibbs; R.J. West. 1981. Shalfow dredging as a strategy for the control of sublittoral macrophytes: a case study in Tuggerah Lakes, New South Wales. Aust. J. Mar. Freshwater Res. 32:563-571. Corns, W.G.; R.K. Gupta. 1968. Mowing experiments with Richardson’s pondweed (Potamogeton richardsonii). Can. Nat. Weed Comm. West. Sect. Res. Rept. pp. 255-56. Crafts, A.S. 1975. Weed control in irrigation and drainage ditches, lakes & streams. In: Modern Weed Control. Berkeley: Univ. California Press, 440pp. pp. 340-57. Culpepper, M.M.; J.L. Decell. 1978. Field Evaluation of the Aqua-Trio System. In: Tech. Rept. A-78-3, Mechanical Har¬ vesting of Aquatic Plants (2 Vols). Vicksburg, MS: U.S. Army Engr. Waterways Expt. Sta. 406pp. Dassanayake, M.D. 1976. Noxious aquatic vegetation control in Sri Lanka. In: Aquatic Weeds in S.E. Asia. ed. by C.K. Varshney & J. Rzoska. Dr. W. Junk Publishers. The Hague, Netherlands. 396pp. pp. 59-61. Dawson, F.H. 1978. Aquatic plant management in semi-nat¬ ural streams: the role of marginal vegetation. J. Environ. Management. 6:213-21. Deutsch, A. 1974. Some equipment for mechanical control of aquatic weeds. International Plant Protec. Center, Oregon State Univ., Corvallis, Oregon. Rep. No. 74-2. 17pp. Druijff, A.H. 1979. Manual and mechanical control of aquatic weeds in water courses. In: Weed Research in Sudan. Vol I: Proc. of a Symp. 152pp. ed. by M.E. Beshir & W. Koch. Wad Medani, Sudan: University of Gezira. pp. 137-145. Dykyjova, D.; S. Jusak. 1973. The influence of summer cut¬ ting on the regeneration of reed. ed. by S. Hejny. Ecosystem Study on Wetland Biome in Czech. IBP/PT-PP Rept. No. 3. pp. 245-50. Eaton, J.W.; K.J. Murphy; T.M. Hyde. 1981. Comparative trials of herbicidal and mechanical control of aquatic weeds in canals. In: Proc. Aquatic Weeds and Their Control, 1981. Oxford, England: Association of Applied biologists. 105-16. F.lser. H I. 1966. Control of water chestnut by machine, in Mary¬ land 1964-65. Proc. 20th Northeast Weed Control Conf., pp. 682-87. Feichtinger, F. 1974. Mechanical ditch maintenance in Aus- ria. Proc. EWRC 4th Intern. Symp. Aquatic Weeds, Wien. 4:84-86. George, M. 1976. Mechanical methods of weed control in water¬ courses: an ecologist's view. Proc. Symp. Aquatic Herbicides. 16:91-99. Haller, W.T.; J.V. Shireman; D.F. Durant. 1980. Fish harvest re¬ sulting from mechanical control of hydrilla. Trans. Am. Fish Soc. 109:517-20. Hernandez, S. 1978. Weeds and their control in Senegal. In: Weeds and Their Controtfn the Humid and Subhumid Tropics, ed. by I.O. Akobundu. Ibandan, Nigeria: Weed Sci. Soc. Nigeria and Inst. Trop. Agr., 421pp. pp. 176-81. Hoogerkamp, M.; G. Rozenboom. 1978. The management of vegetation on the slopes of waterways in the Netherlands. Proc. European Weed Res. Soc. Symp. Aquatic Weeds, pp. 203-11. Hutto, T.D. 1982. Simulation modeling of mechanical control systems. In: Proc. 16th Annu. Meet. Aquat. Plant Control Res. Planning and Operations Review. U.S. Army Engineer Water¬ ways Experiment Station, Vicksburg, Mississippi. Misc. paper A-82-3. pp. 33-50. Johnson. R.E.; M.R. Bagwell. 1979. Effects of mechanical cut¬ ting on submersed vegetation in a Louisiana lake. J. Aquat. Plant Manag. 17:54-57. Kemmerling, W. 1974. The importance of building yards for the maintenance of aquatic systems. Proc. EWRC 4th Intern. Symp. Aquatic Weeds, Wien. 4:87-95. Kimbel, J.C.; S.R. Carpenter. 1981. Effects of mechanical har¬ vesting on Myriophyllum spicatum L. regrowth and carbohy¬ drate allocation to roots and shoots. Aquat. Bot. 11(2): 121-27. Koegel, R.G.; D.F. Livermore; H.D. Bruhn. 1977. Costs and productivity in harvesting of aquatic plants. J. Aquat. Plant Manag. 15:12-17. Koegel, R.G.; D.F. Livermore; H.D. Bruhn; P.D. Bautz. 1973. Improving surface water conditions through control and dis¬ posal of aquatic vegetation. Phase II. Univ. Wisconsin Tech. Completlion Rep. Proj. No. OWRR B-058-WIS. 59pp. Koegel, R.G.; D.F. Livermore; H.D. Bruhn. 1974. Aquatic plant harvesting: economic, technical, and management as¬ pects. Paper No. 75-5518, Dec. 1974. Amer. Soc. Agric. Engin. St. Joseph, MO. Koegel, R.G.; D.F. Livermore. 1979. Reducing capital invest¬ ment in aquatic plant harvesting systems. In: Aquatic Plants, lake Management, and Ecosystem Consequences of Lake Har¬ vesting. ed. by J. Breck; R. Prentki, and O. Loucks. Insti¬ tute for Environmental Studies, Univ. of Wisconsin, Madison Wisconsin, pp. 329-338. Kozloff, A.V. 1973. A comparison of current aquatic vegeta¬ tion control methods. Irvine, California. 23pp. Krinke, H.; I. Dyckova. 1974. Films on embankment mowing machinery. Proc. EWRC Intern. Symp. Aquatic Weeds, Wien. 4:96-106. Lagarde, V.E. 1980. Water depth limitations in mechanical harvester use in the St. Johns River, Florida. Aquatic Plant Control Res. Prog. Information Exchange Bull. A-80-1. 6 pp. Lange, S.R. 1965. The control of aquatic plants by commercial harvesting, processing, and marketing. Proc. S. Weed Conf. 18:536-37. Livermore, D.F.; H.D. Bruhn; B.W. Pollock. 1970. Processing characteristics of subsurface macrophytes of Madison, Wis¬ consin lakes in relation to mechanical harvesting systems. U.S Office Water Resources Res. Tech. Rept. OWRR B-018-WIS. 12pp. Livermore, D.F.; R.G. Koegel; H.D. Bruhn. 1975. Aquatic plant harvesting: development of high-speed harvesters and processing and utilization of harvested vegetation. Univ. Wisconsin Water Resources Center Technical Report. Wis WRC 75-02, 46pp. Livingstone, F.C. 1970. Water weed cutter redesigned. Water Sewage Works. 1 1 7(3 ):89. Loucks, O.L. 1979. Conference findings: an overview. In: Aquat¬ ic Plants, Lake Management, and Ecosytem Consequences of Lake Harvesting, ed. by J. Breck; R. Prentki, and O. Loucks. Insti¬ tute for Environmental Studies, Univ. of Wisconsin, Madison, Wisconsin, pp. 421-434 Maneewarn. T. 1974. H-650 Aquatic weed cutter. In: Proc Aquatic Weed Seminar. Nonthaburi: Electricity Generating Authority of Thailand (Egat). p. 100. Mara, M.J. 1976. Estimated costs of mechanical control of water hyacinths. J. Environ. Econ. Management. 2(4):273-94. Maxnuk, M.D. 1979. Studies on aquatic macrophytes. Part XXII. Evaluation of rotavating and diver dredging for aquatic weed control in the Okanagan Valley. Province of British Col¬ umbia, Ministry of the Environment, Water Investigations Branch. 53pp. McGehee, J.T. 1979. Mechanical hydrilla control in Orange Lake, Florida. J. Aquatic Plant Manag. 17:58-61. Miller, A. 1981. Prediction of hydrilla growth and biomass for mechanical harvesting operations. In: Proc. 15th Annu. Meet. Aquat. Plant Control Res. Planning and Operations Review. U.S. Army Engineer Waterways Experiment Station, Vicksburg, Mis¬ sissippi. Misc. Paper A-81-3. pp. 224-240. Mitchell, D.S. 1979. Formulating aquatic weed management programs. J. Aquat. Plant Management. 17:22-24. Municipality of Metropolitan Seattle. 1982. Milfoil har¬ vesting program report 1980-81. METRO, Seattle, WA. 33 pp. Murfitt, R.F.A. 1981. Some unanswered questions relating to the mechanical control of weeds in water channels. In: proc. of the Conf. Aquat. Weeds and Their Control, ed. by R.J. Makepeace. Wellesbourne, Warwick: Assoc. Appl. Biol. pp. 87-94. Murphy, K.J.; J.W. Eaton. 1980. A survey of aquatic weed growth and control in the canals and river navigations of the British waterways board. Dept, of Botany, Univ. of Liverpool. 1980 British Crop Protection Conference-Weeds, pp. 707-714. Murphy, K.J.; J.W. Eaton. 1981. Ecological effects of four herbicides and two mechanical clearance methods used for aquatic weed control in canals. In: Proc. of the Conf. Aquat. Weeds and their Control, ed. by R.J. Makepeace. Wellesbourne, Warwick: Assoc. Appl. Biol. pp. 201-17. Musil, C.F.; C.M. Breen. 1977. The applications of growth kinetics to the control of Eichhornia crassipes (Mart.) Solms. through nutrient removal by mechanical harvesting. Hydro- biologia. 53(2):165-71. Neil, J.H. 1980. Mechanical control technology development: a computer model and systems cost analysis of the limnos aquatic plant harvesting system. Proc. 14th Ann. Meet. Aquat. Plant Control Res. Plan, and Operations Rev. Misc. Paper A-80-3. Vicksburg, Mississippi. U.S. Army Engr. Water¬ ways Expt. Sta. pp. 157-69. Newroth, P.R. 1974. Studies on aquatic macrophytes. Part V. Aspects of aquatic weed control by mechanical harvester. Vic¬ toria, British Columbia: Water Investigations Branch, British Columbia Water Resources Service. Dept. Lands Forests & Water Resources. 54pp. Nichols, S.A. 1971. The effects of harvesting aquatic macro¬ phytes on algae. Trans. Wisconsin Acad. Sci- 61:165-173. Nichols, S.A. 1974. Mechanical and habitat manipulation for aquatic plant management: a review of techniques. Wisconsin Dept. Nat. Resources. Tech. Bull. 77:34 pp. Perkins, M.A.; M.D. Sytsma. 1981. Efficacy of mechanical harvesting and its influence upon carbohydrate accumula¬ tion in Eurasian watermilfoil. In: Proc. 15th Annu. Meet. Aquat. Plant Control Res. Planning and Operations Review. U.S. Army Engineer Waterways Experiment Station, Vicks¬ burg, Mississippi. Misc. Paper A-81-3. pp. 464-479. Perrier, E.R.; A.C. Gibson. 1982. Simulation for harvesting of aquatic plants. U.S. Army Engineer Waterways Experiment Station. Vicksburg, Mississippi. Tech. Rept. A-82-1. 54pp. Peterson, S.A.; W.L. Smith; K.W. Malueg. 1974. Full-scale harvest of aquatic plants: nutrient removal from a eutrophic lake. Water Poll. Control Fed. 46(4):697-707. Peverly, J.H. 1974. Effects of shading, cutting, and root-bed disruption on aquatic plant growth. Dept. Agronomy Mimeo 17. Ithaca, N.Y.: Cornell University, p.13. Phillippy, C.L.; J.M. Perryman. 1972. Mechanical harvest¬ ing of water hyacinth (Eichhornia crassipes) in Gant Lake Canal, Sumter County, Florida. Tallahassee, Florida: Florida Game and Freshwater Fish Commission. 9pp. Appendixes A-F. Price, H. 1981. A review of current mechanical methods. In: Proc. of the Conf. Aquat. Weeds and Their Control. Ed. by R.J. Makepeace. Wellesbourne, Warwick: Assoc. Appl. Biol. pp. 77-86. Queijo, J. 1977. Harvesting a nusiance. Environment 19(2) Robinson, S.C. 1975. The design of a collection system to remove cut vegetation from Buffalo Lake. April 1975. Univ. Wis¬ consin, Madison, Wise. Robson, T.O. 1974. The control of aquatic weeds - mechanical control. UNESCO, ed. by D.S. Mitchell. Paris, pp. 72-85. Sabol, B.M. 1982. Field test of aquatic disposal of chopped hydrilla. In: Proc. 16th Annu. Meet. Aquat. Plant Control Res. Planning and Operations Review. U.S. Army Engineers Water¬ ways Experiment Station, Vicksburg, Mississippi. Misc. Paper A-82-3. pp. 25-32. Sassic, N.M. 1982. Harvesting: the future of aquatic plant con¬ trol? Aquatic 4(1 ):14, 16. Sharma, K.P. 1977. Effect of cutting on the growth and flower¬ ing behavior of Typha elephantina roxb. Curr,Sci.47(8):275-276. Shekhov, A.G. 1974. Effect of cutting time on renewal of stands of reed and cattail. Hydrobiol. J. 10(3):45-48. Smith, J.L. 1981. Field tests of the limnos mechanical har¬ vesting system. In: Proc. 15th Annu. Meet. Aquat. Plant Control Res. Planning and Operations Review. U.S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi. Misc. Paper A-81-3. pp. 181-196. Smith, P.A. 1978. Mechanical harvesting of aquatic plants: report 2, evaluation of selected handling functions of mechanical control. Aquatic Plant control Res. Program Tech. Rept. A-78-3. Vicksburg, Mississippi: U.S. Army Engineer Waterways Exper¬ iment Station Environmental Lab. 121pp. Solomons, W.B. 1938. A simple weed cutter for ponds. Progres¬ sive Fish Culturist. 41:20-22. Stewart, J.S. III. 1972. Energy and flow requirements for chopping water hyacinths. Master’s Thesis Univ. of Florida, Gainesville. 47pp. Szumiec. J. 1963. The influence of emergent vegetation and the manner of its mowing on the bottom fauna of fish ponds. Acta Hydrobiol. (IN POLISH). 5:315-335. Taussig, J.K. 1969. The development cycle of a hydraulic aquat¬ ic weed control device. Proc. Northeast Weed Control Conf. 23:367-74. Timmons, F.L. 1952. Results with chemical and mechanical methods of controlling common cattail (Typha latifolia). Progr. Rept. Western Weed Control Conf. 13:141-43. Timmons, F.L. 1954. Use of underwater mower for control of cattails and water lily. West Weed Conf. Newsletter. 2:17-18. Touzeau, L.J. 1972. Mechanical water hyacinth removal op¬ erations, Aquamarine Corporatlion, Blufton, Florida. Florida Game Freshwater Comm. Tallahassee, Florida 13pp. Van Dyke, J.M. 1971. Mechanical harvesting of water hya¬ cinth in Shell Creek Reservoir, Charlotte County, Florida. Florida Game Freshwater Fish Comm. Tallahassee, Florida 25pp. Velu, M. 1976. Development of equipment for eradication of aquatic weeds. In: Aquatic Weeds in South East Asia. ed. by C.K. Varshney & J. Rzoska. Dr. W. Junk Publishers. The Hague, Nether¬ lands. pp. 233-240. Velu, M. 1969. A mechanical device for eradication of sub¬ merged aquatic weeds. Fishery Technol. 6( 1 ): 18-25 . Wade. P.M. 1978. The effect of mechanical excavators on the drainage channel habitat. Proc. European Weed Res. Soc. Symp. Aquatic Weed. 5:333-342. Webb, D.J.; R.F. Harbord. 1964. A mechanical cleaner for trans¬ port canals. Span. 7:40-41. West, H.W. 1980. Mechanical control technology development: an overview. Proc. 14th Ann. Meeting, Aquat. Plant Control Res. Planning and Operations Rev. Misc. Paper A-80-3. U.S. Army Engr. Waterways Expt. Sta. Vicksburg, Mississippi, pp. 152-6. Whickliff, E.L. 1925. Methods of controlling undesirable aquat¬ ic plants in ponds, lakes, and other quiet waters. Ohio Dept, of Agr. Bur. Fish Game. Bull. 20-C, 2pp. Wile, I. 1974. Lake restoration through mechanical harvesting of aquatic vegetation. Verhandl. Intern. Verein. Limnol. 19(1):660-71. Wile, 1. 1978. Environmental effects of mechanical harvesting of aquatic vegetation. Verhandl. Intern. Verein. Limnol 19(1):660-71. Wile, 1. 1978. Environmental effects of mechanical harvesting. J. Aquat. Plant Manag. 16:14-20. Woods, J.W. 1970. Mechanical removal and utilization of aquat¬ ic plants. Florida’s Aquatic Weed Nenace, Proc. Aquatic Plant Res. Conf. governor’s Aquatic Res. & Develop. Comm. Gainesville, Florida, pp. 10-15. Wunderlich, W.E. 1967. The use of machinery in the control of aquatic vegetation. Hyacinth Control J. 6:22-24. Wunderlich, W.E. 1938. Mechanical hyacinth destruction. Mili¬ tary Eng. 30:5-10. Yount, J.L.; R.A. Crossman. 1970. Eutrophication control by plant harvesting. J. Water Pollution Control Federation. PT. 2. 42(5):173-83. Zeiger, C.F. 1966. New equpment developed by the corps of engin¬ eers - for use in aquatic weed control. Weed Soc. Am. Meeting. 6:93 AQUAPHYTE FALL 1982 PAGE 7 NEW PATHWAY FOR HYDRILLA? Hydrilla verticillata is included in many of "the world’s worst aquatic weeds" lists. An explosive grower, hydrilla has in recent years clogged rivers and lakes in many parts of the world, displacing water, slow¬ ing water flow, interfering with boat com¬ merce, outcompeting native plant species and, not least of all, intercepting sun¬ light used by plants and animals which eventually are eliminated from beneath its stringy mats. In Florida, hydrilla and water hyacinth (Eichhornia crassipes) now vie for top spot as the state’s worst aquatic invader. It is estimated that hydrilla infests 25% of Florida's thousands of miles of waterways, though its first Florida disovery was only about 20 years ago. Hydrilla has now been reported in most continents with the not¬ able exception of South America. Dr. George Bowes examining PEP car boxylase enzyme data on a Cary 219 UV Visible Spectrophotometer. BOOKS STUDIES ON AQUATIC VASCULAR PLANTS. Proceedings of the International Colloqium on Aquatic Vascular Plants, Brus¬ sels, 1981. Edited by J.J. Symoens, S.S. Hooper and P. Compere. Otto Koeltz Science Publishers, P.O. Box 1380, D-6240 Koenig- stein, Federal Republic of Germany. More than 418 pages. DM 100.00. This book is a collection of 69 colloquium presentations arranged in the following sections: Systematics-Morphology; Physi¬ ology-Reproduction Strategies; Ecology- Community Metabolism and Production; Phytosociology-Distribution; Water Qual¬ ity-Weed Control; and Regression-Introduc¬ tion-Conservation. CHEMICAL AND TROPHIC STATE CHARACTERISTICS OF FLORIDA LAKES IN RELATION TO REGIONAL GEOLOGY. Prepared by Daniel E. Canfield, Jr., Project Leader. 1981. Center for Aquatic Weeds, University of Florida, Gainesville, Florida, USA. 444 pages. This is a limnological survey of the chem¬ ical and trophic state characteristics of 165 of Florida s more than 7,700 lakes. Cli¬ mate, geology, water chemistry, water qual¬ ity and chlorophyll a concentrations for all 165 lakes is presented. Though the lakes range from ultra-oligotrphic to hyper- George Bowes, University of Florida bot¬ any professor associated with the Center for Aquatic Weeds, is investigating a key to hydrilla’s competitive edge: it’s photo¬ synthetic mechanism. Among hydrilla’s novel photosynthetic properties is its ability to adapt to different light con¬ ditions. It has a low light compensation point, which enables its photosynthesis to be driven at a lower light energy input than that required for many native species. Another important feature is hydrilla’s ability to alter its photosynthetic car¬ bon fixation pathway in response to en¬ vironmental growth conditions, thus max¬ imizing its photosynthetic efficiency. The known photosynthetic pathways for ter¬ restrial plants, termed C3 and C4, do not accomodate hydrilla’s photosynthesis. Hy¬ drilla’s pathway apparently incorporates elements of both the C3 and C4 modes, and Bowes has proposed that hydrilla and some other submersed aquatic macrophytes (SAM species] represent a previously unrecognized photosynthetic category. Currently, Bowes is investigating the enzymes of hydrilla leaves using immun¬ ological techniques to pinpoint their exact location, and thereby further understand how hydrilla’s novel pathway compares to the classical C3 and C4 systems. Dr. Bowes believes that the unique ability of hydrilla to switch photosynthetic pathways has wider implications than just for aquatic weed research, in that it could prove to be a key to improving the photosynthetic ef¬ ficiency, and thus productivity, of many crop plants with the C3 pathway, when genetic engineering techniques become feasible. Dr. Bowes’ address is 3157 McCarty Hall, University of Florida, Gainesville, Florida, 32611, USA. eutrophic, the report states, "As a group, Florida lakes can be characterized as pro¬ ductive, soft-water lakes." CLASSIFICATION OF WETLANDS AND DEEPWATER HABITATS OF THE UNITED STATES. L.M. Cowardin, V. Car¬ ter, F.C. Golet, E.T. LaRoe. 1979. Fish and Wildlife Service, U.S. Department of the In¬ terior. 103 pages. This new system has become the official wetland classification system of the Fish and Wildlife Service. The five systems and their subsystems are described. Within the subsystems, classes are described. Classes are based on substrate material and flooding regime, or on vegetative life form. Keys to the systems and classes are included. Photo¬ graphs depicting 56 different classifications are included. INVERTEBRATES AND VERTEBRATES ATTACKING COMMON REED STANDS (Phragmites communis] IN CZECH¬ OSLOVAKIA. V. Skuhravy, V. Pokorny, J. Pelikan, M. Skuhrava, K. Hudec, B. Rych- novsky. 1981. Academia nakaladatelstvi Ceskoslovenske Akademie ved, Praha. 113 pages. Reed is an economic plant in Czechoslov¬ akia, grown for cellulose production. This is a collection of descriptions of reed’s prin¬ WEST AFRICAN WEED SCIENCE SOCIETY The West African Weed Science Society’s second international conference is sched¬ uled to be held October 17-22, 1983 at Abidjan (Ivory Coast). Theme of the con¬ ference is "The weeds in tropical areas: knowledge and control" The English/French conference will fea¬ ture technical sessions on the following topics: • botany, taxonomy • biology, ecology • competition and allelopathy • weed control in agricultural crops • weeding equipment • special methods of weed control • herbicides and residues in soil and plants • herbicides and environment: safety in use Organizers of the conference ask that in¬ terested parties contact them by October, 1982. A second circular will be available in November, 1982. Contact Mr. P. Marnotte Idessa, Secretary and Treasurer, DVC BP 635, Bouake, IVORY COAST. Chairman of the Organizing Committee: Prof. Tchoume M. Ensa 08 BP. 35 Abidjan 08 IVORY COAST Coordinating member of the Organizing Committee: Mr. B. Mallet Ctft 08 BP. 8033 Abidjan 08, IVORY COAST cipal pests, their development (biology and ecology] and their influence on reed produc¬ tion. Included are data on their distribu¬ tion in Czechoslovakia and Europe. Among reed’s principal pests are the caterpillar Archanara geminipuncta, flies of the genus Lipara, gall midges, Platycephala plani- fro ns, the mite Steneotarsonemus phrag- mitidis, as well as the muskrat, water vole and the greylag goose, Anser anser. IMPROVING TECHNOLOGY FOR CHEM¬ ICAL CONTROL OF AQUATIC PLANTS. K.K. Steward. 1982. Misc. Paper A-82-4, prepared by Aquatic Plant Management Laboratory, U.S.D.A., Science and Education Administration, Fort Lauderdale, Florida, for the U.S. Army Engineer Waterways Exper¬ iment Station, CE, Vicksburg, Mississippi. 52 pages. Responding to the "need to modify exist¬ ing aquatic herbicide evaluation techniques," +his protocol describes procedures for eval¬ uating conventional and controlled-release herbicides. Three CR formulations, one coded-confidential compound, one growth retardant and six conventional herbi- cidal formulations are evaluated. Also, iron chelates were evaluated for enhancing effi¬ cacy of diquat and potassium endothall against hydrilla. Eleven aquatic plants were treated with herbicides in the course of this study. PAGE 8 AQUAPHYTE FALL 1982 INTERNATIONAL CONFERENCE ON WATER HYACINTH An International Conference on Water Hy¬ acinth is scheduled for February 7-11, 1983 in Hyderabad, India. It is sponsored by the Council of Scientific and Industrial Research (India), the Commonwealth Science Council (London) and the United Nations Environ¬ ment Programme (Nairobi). The Conference is timed to synchronize with the conclusion of the CSC-UNEP Man¬ agement of Water Hyacinth Project and its final review. The Conference language will be English and the following topics will be discussed: Environment and Ecology, Biology, Chem¬ istry, Engineering, Utilization, Control and International Cooperation. Registration fee is $100 (US). Registra¬ tion form and fee should reach the Confer¬ ence Secretariat before November 30, 1982. Thereafter, the fee will be $110 (US). Dead¬ line for submission of abstracts is October 15, 1982. All correspondence concerning the Confer¬ ence should be addressed to: International Conference on Water Hyacinth c/o Dr. G. Thyagarajan Director, Regional Research Laboatory Hyderabad 500 009 INDIA AQUATIC PLANT MANAGEMENT SOCIETY 1982-83 OFFICERS President: Emory McKeithen, Union Carbide Cor¬ poration, Jackson, Mississippi, USA. President-Elect: A. Leon Bates, Tennessee Valley Author¬ ity, Muscle Shoals, Alabama, USA. Vice-President: Max McCowen, Elanco Products, Inc., Greenfield, Indiana, USA. Past-President: Roy P. Clark, Environmental Protection Agency, Atlanta, Georgia, USA. Secretary-T reasurer: William N. Rushing, U.S. Army Corps Waterways Experiment Station, Vicks¬ burg, Mississippi, USA. Editor, Journal of Aquatic Plant Management: William T. Haller, Center for Aquatic Weeds, Gainesville Florida, USA. Newsletter Editor: L.V. Guerra, Texas Parks and Wildlife, San Antonio, Texas, USA. Aquatic Plant Management Society: P.O. Box 16, Vicksburg, MISS. 39180/USA NEW ZEALAND LAKES The well-being of New Zealand’s lakes, especially the Rotorua lakes, is the main in¬ terest of The Lake Weed Control Society, according to its secretary, Denis F. Dunlop. Aquatic weeds, such as Lagarosiphon major, "affect the tourist industries as well as the lives and intersts of people living hereabouts." These lakes are well-known for their rainbow trout angling. Reservoirs behind New Zealand’s hydro¬ electric dams are also threatened by aquatic weeds, according to Dunlop. Block¬ age of intake screens of the dams and capa¬ city reduction of the reservoirs are some of the problems directly attributable to aquatic weed infestation. The fact that hydro-electric dams are the main sources of energy for New Zealand emphasizes the fundamental nature of their aquatic weed problems. Lagarosiphon major For more information on the activities of The Lake Weed Control Society, write: R.D.4, Otaramarae, Rotorua, NEW ZEALAND. SHORT COURSE SUCCESS The Aquatic Weed Short Course held June 21-25 at the University of Florida, was attended by more than 100 researchers, teachers and field personnel. The sessions served to update the aquatic weed control community in the latest infor¬ mation about the spread, ecology, environ¬ mental effects, government regulations and recent developments in the chemical, mech¬ anical and biological controls of aquatic weeds. Organizers Vernon Vandiver and William Haller expect to repeat the course in June, 1984. Dr. William T. Haller updates the conference audience on the use of several of the newer aquatic herbicides.