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Myriophyllum spicatum L. (Eurasian watermilfoil, hereafter called milfoil) is one of many invasive plant species that are investigated by biocontrol researchers at the U.S. Army Engineer Research and Development Center, Environmental Laboratory (EL). For the past 10 years, plant samples from healthy, declining, or debilitated milfoil populations have been field-collected or have been sent to the EL specifically requesting microbial analysis, often in an attempt to explain sudden population declines. As a result of assaying the plant material for pathogens, lists of fungi associated with milfoil at each collecting site were compiled. It became apparent after examining the lists that certain fungal organisms were consistently isolated from the samples at high frequencies regardless of the condition of the host. The potential biological control pathogens were subjected to a screening regime for efficacy on milfoil.

The aquatic herbicide Sonar AS (fluridone) is being used in Northern tier states to selectively control the submersed exotic species Eurasian watermilfoil (Myrtophyllum spicatum L.) growing in lakes and reservoirs. Reliable quantitative information linking changes in the submersed plant community following fluridone applications is limited, particularly with respect to water residue records; therefore, a study was conducted to investigate the impact of low-dose fluridone treatments on the aquatic plant communities in eight lakes of southern Michigan The main objective of the study was to determine whether submersed plant species diversity and frequency were impacted by low-dose fluridone applications in the year of treatment, when targeting for Eurasian watermilfoil control. Secondary objectives included (a) determining fluridone effectiveness on the exotic submersed species curiyleafpondweed (Potamogeton cnspus L.), (b) evaluating shifts in plant species diversity at 1-year posttreatment, (c) measuring the effect of thermal stratification on water column distribution of fluridone residues, and (d) verifying laboratory-derived results of fluridone concentration and exposure time relationships with respect to efficacy against Eurasian watermilfoil.

Euhrychiopsis lecontei (Dietz) is a small native weevil that feeds on various species of watermilfoil. Its natural host is northern watermilfoil (Myriophyllum sibiricum Komarov); however, it has been shown to feed extensively on Eurasian watermilfoil (Myriophyllum spicatum L.). The ability of this insect to feed on and damage Eurasian watermilfoil has led to its use in the management of this non- indigenous plant. Euhrychiopsis Iecontei is a weevil in the family Curculionidae. It exhibits development in four distinct stages; egg, larva, pupa, and adult.

A simulation model for biomass dynamics of the submersed macrophyte Myriophyllum spicatum is presented. The model (MILFO) is based on carbon flow through the vegetation in meter-squared (cu m) water columns. It includes descriptions of several factors that affect biomass dynamics, such as site-characteristic changes in climate, water temperature, water transparency, pH and oxygen effects on CO2 assimilation rate at light saturation, wintering strategies, grazing and mechanical control (removal of shoot biomass), and of latitude. The characteristics of the community and of the site can be easily modified by the user. MILFO incorporates insights into the processes affecting the dynamics of an Eurasian watermilfoil community in relatively shallow, hard water (0.5-6 m depth; DIC concentration > 0.8 mmol and pH ranging from 7.6 to 9.4) under ample supply of nitrogen and phosphorus in a pest-, disease-, and competitor-free environment under the prevailing weather conditions. It has been calibrated on data pertaining to a milfoil community in Lake Wingra, Wisconsin, USA. At that site, growth starts from the basal rhizome/root crown system, alone or with wintering shoot biomass present. Shoot biomass usually peaks twice a year, in June originating from the first plant cohort and in August from the second cohort, and intensive downward transport of soluble carbohydrates occurs after anthesis of each cohort, replenishing the rhizome/root crown system. In a tropical climate, a third plant cohort is active. MILFO simulated the dynamics of plant and rhizome/root crown biomass at Lake Wingra well over a period of 1 to 5 years. It has been used to calculate plant and rhizome/root crown biomass for the same latitude in a different year and for other latitudes in temperature (Alabama, USA) and tropical (India) areas, where it simulated biomass ranges similar to those measured in the field.

This manual has been written as a practical guide for the operational use of MILFO (version 1.0), a personal computer-based software package that simulates growth of Eurasian watermilfoil. This manual includes instruction for installing and using the MILFO software package as well as example runs to provide further information to facilitate proper execution and to demonstrate applications.

This technical note describes screening of fungal pathogens collected in The People's Republic of China for efficacy on hydrilla (Hydrilla verticillata (L.f.) Royle) and Eurasian watermilfoil or milfoil (Myriophyllum spicatum L.). Results of this research will be used to determine the direction of future efforts in using classical pathogen biological control research for management of these two nuisance aquatic weed species.

A better understanding of factors related to invasion and colonization success of exotic species might improve both planning and implementation of management for invasions in new areas. Data from lakes containing Eurasian watermilfoil were evaluated to compare the extent of Eurasian watermilfoil dominance to common limnological parameters. The best predictors of Eurasian watermilfoil dominance were water column total phosphorus and Carlson's Trophic State Index. This analysis corroborates observations that Eurasian watermilfoil appears most abundant in mesotrophic lakes and moderately eutrophic lakes. An application of this model to an ecological classification of Minnesota lakes suggests that a large proportion of lakes in Minnesota across a broad geographical area could support significant infestations of Eurasian watermilfoil.

The U.S. Army Corps of Engineers (CE) Aquatic Plant Control Research Program (APCRP) is the Nation's only federally authorized research program directed to develop technology for the management of non-indigenous aquatic plant species. The APCRP is designed to provide effective, economical, and environmentally compatible methods for assessing and managing problem aquatic plants that interfere with the valued uses of the waterways of the United States. Research efforts are currently focused on the development of advanced management strategies and applications for the submersed aquatic plants, hydrilla (Hydrilla verticillata (L.f.) Royle) and Eurasian watermilfoil (Mynophyllurn spicatum L.). The APCRP is committed to the development, transfer; and implementation of aquatic plant management technologies, and will continue to lead the Nation in the future.

Seasonal biomass and carbohydrate allocation patterns of Eurasian watermilfoil (Myriophyllum spicatum L.) were evaluated to elucidate potential points in the seasonal phenological cycle for improved control. Eurasian watermilfoil was sampled from outdoor 0.3-ha ponds in Lewisville, TX, from January 1991 to December 1993 and analyzed for free sugars, starch, and total nonstructural carbohydrates (TNC). Root crowns stored up to 30-percent TNC, followed by autofragments (25 percent), lower stems (22 percent), and upper stems and inflorescences (12 percent). Low levels of stored carbohydrates occurred in July 1991, April 1992, and May 1993. Low levels of stored carbohydrates also were observed in October for all 3 years. Low points in carbohydrate storage might be exploited to improve management of Eurasian watermilfoil., Aquatic Plant Control Research Program.

A search for insects and diseases which attack Eurasian watermilfoil (Myriophyllum spicatum L.), waterchestnut (Trapa natans L.) and hydrilla (Hydrilla verticillata Royle) that are the noxious water weeds in the US was made from the literature, taxonomic collections and through consultations with specialists. Totally, 32 insect and 7 fungi species associated with the targeted weeds were found on the territory of the former Soviet Union. Most of Insecta are Coleoptera (14 species) and Lepidoptera (7 species). Besides, 5 Diptera, 4 Trichoptera, and 2 Homoptera species were revealed. Majority of above mentioned insects and all fungi are connected with M. spicatum (28 species). particularly, three weevil species: Phytobius leucogaster, Pelenomus canaliculatus and Baqous geniculatus, which are reportedly oligophagous on Myriophyllum spp. may be considered as potential biocontrol agents.

The use of classical biocontrol techniques for milfoil management was not a viable option when the Joint Agency Guntersville Project sponsored by the Tennessee Valley Authority and Headquarters, U.S. Army Corps of Engineers began. No host specific insects had been approved for release, and overseas searches for pathogens had not yet been initiated. A microbial biocontrol strategy, the inundative method, utilizing an endemic plant pathogen, Mycoleptodiscus terrestris (Gerd.) Ostazeski (Mt), known to be a parasite on milfoil, was proposed. Introduction of microbes for biological control purposes against nuisance pest populations is strictly regulated by individual State agencies and two Federal agencies, including the U.S. Environmental Protection Agency and Agriculture Protection Health Inspection Service. The use of a pathogen that is known to be endemic within a State lessens the fear associated with introducing a microbe into a new area. Surveys were conducted on Lake Guntersville Reservoir to provide documentation on pathogens of milfoil to facilitate the permitting process from State and Federal agencies., Aquatic Plant Control Research Program.

Aquatic plant species that form dense floating canopies or mats at water surface often negatively impact the ecological and economic values of a water body. In Guntersville Reservoir, this growth form is exhibited by both the weedy, nonnative aquatic macrophyte Myriophyllum spicatum (Eurasian watermilfoil) and the nuisance, albeit native, mat-forming cyanobacteria Lyngbya wollei (Iyngbya). In contrast to the few species that cause problems, most native aquatic plant species exhibit growth forms that enhance water quality and/or habitat values of the aquatic systems. In addition, greenhouse and pond reserch have indicated that established populations of native aquatic plants serve to minimize or prevent establishment of less desirable species. This report presents results of field trials designed to test the central hypothesis that small populations of native plants, deliberately established in areas experiencing or subject to infestation by one of the two nuisance species in Guntersville Reservoir, are able to survive and ameliorate the negative impacts of nuisance species. One aspect of this research examined the ability of established plots of three native species to withstand reinvasion by M. spicatum. Small plots of the native submersed species Vallisneria americana (wild celery), the floating-leaved species Potamogeton nodosus (American pondweed), and the floating-leaved/emergent species Nelumbo Lu tea (American lotus) were established during a general decline of M. spicatum in Guntersville Reservoir. This offered the opponunity to examine the potential of these species for preventing reinfestation of M. spicatum as it regrew within the reservoir. Although establishment of the natives was complicated by high herbivory pressures, results indicate that established plots of V. americana and N. Jutea significantly reduced the regrowth of M. spicatum relative to

A technical meeting entitled "Physiological Assessment of Herbicide Stress in Aquatic Plants" was held 10 Jun 1993 at the U.S. Army Engineer Waterways Experiment Station by the Chemical Control Technology Team (CCTT) under the Aquatic Plant Control Research Program. Scientists from universities and government research facilities with common research interests in chemical control of plants and in aquatic weed physiology and ecology were invited to discuss physiological and biochemical methods of verifying and monitoring herbicide effects in submersed aquatic plants. This report summarizes the presentations and discussions by participants on general guidelines for choosing optimal assessment parameters and their suggestions for rapid and simple assays suitable for monitoring physiological changes, whether produced directly by the mode of action of aquatic herbicides or indirectly as a result of loss of metabolic function. Those assays expected to be readily implemented by the CCTT for research assessments of efficacy on target, nontarget, or off-target populations are briefly described.

The purpose of this supplement to the Environmental Impact Statement (EIS, 1979) for the Aquatic Plant Management Program (APMP) is to review and update both geographic and treatment-related program in the treating of aquatic infestations of Eurasian Watermilfoil (Myriophyllum spicatum) and advancement of the state of the science of aquatic plant management. The purpose of the APMP is to prevent the spread of watermilfoil and to alleviate negative consequences of thick growth of the plant, such as diminished accessibility and desirability of water bodies for public recreational use, increased public costs for cleaning accumulations of plant material at dams, obstruction of drainage, restriction of natural water flows, reduced navigability, and damages to fishes and wildlife habitats. Methods for decreasing the spread of watermilfoil include: mechanical harvesting and handpulling, bottom tillage or rotovation; bottom barriers, suction dredging, chemicals such as fluridon or endothall, biological control methods (herbivorous fish and insects, pathogenic microorganisms, and competitive plants, and integrated control methods (using two or more of the above methods).

Phenology and carbohydrate literature for waterhyacinth (Eichhornia crassipes (Mart.) Solms), hydrilla (Hydrilla verticillata L.f. Royle), Eurasian watermilfoil (Myriophyllum spicatum L.), and alligatorweed (Alternanthera philoxeroides (Mart.) Griesb) was surveyed to assess the feasibility of using phenology/carbohydrate relationships for improving control tactics. Many studies have examined phenology of waterhyacinth, hydrilla, and Eurasian watermilfoil, but not alligatorweed. Phenology of monoecious and dioecious biotypes of hydrilla differs in growth pattern and propagule development. The monoecious biotype appears to be better adapted than the dioecious biotype to live at Northern latitudes because of its ability to produce more tubers and turions at lower water temperatures. A few investigations involving Eurasian watermilfoil and alligatorweed suggested that control efforts directed at the low ebb of carbohydrates will decrease biomass production. Little information on carbohydrate partitioning has been reported for waterhyacinth and hydrilla. Previous studies of these plants have not evaluated the role of starch reserves for plant survival. Environmental factors (e.g., temperature, light, and nutrients) have been shown to influence phenology and, by inference, carbohydrate partitioning. How these factors control carbohydrate partitioning in these plants is unknown. Phenological and carbohydrate relationships have not been fully developed to allow plant control programs to take advantage of weak points in a plant's life cycle. Keywords: Weed control; Aquatic weeds.

A survey of the continental United States for pathogens of Myriophyllum spicatum (Eurasian watermilfoil) was conducted. More than 50 water bodies, located in 10 states, were sampled for diseased plants. Sample sites represented a geographic and climatic cross section of aquatic systems in the continental United States, including ponds, lakes, reservoirs, rivers, and canals. At the conclusion of the survey, 792 isolates had been collected from tissue samples and maintained in pure culture. Of these, 462 were bacteria and 330 were fungi; many isolates were duplicates but were retained because they possibly represented different strains of the same species. Lytic enzyme assays indicated that 14 bacterial and 22 fungal isolates produced pectinase or cellulose. Enzyme assays were used to screen for the more promising isolates for additional study as potential biocontrol agents for the management of Eurasian watermilfoil. The 32 isolates were then assayed healthy sprigs of the target species in test tubes. Results indicated that five fungal isolates should be considered for additional study.

Herbicide concentration and exposure time relationships were developed for 2,4-D and the control of Eurasian watermilfoil (Myriophyllum spicatum L.), under laboratory conditions using concentrations, exposure times, and biomass similar to field conditions. Fourteen 2,4-D concentrations (0.5,1.0, and 2.0 mg acid equivalent (ae)/l) and exposure time (12, 24, 36, 48, 60, and 72 hr) combinations were tested. Eurasian watermilfoil control was based on plant injury incurred, relative to that of untreated plants, and harvested biomass (4 weeks after treatment). Plant injury increased with increasing concentrations and exposure times to a threshold above which control was achieved. Severe Eurasian watermilfoil injury occurred in the 0.5 mg ae/l for 72-hr, 1.0 mg ae/l for 36-hr, and 2.0 mg ae/l for 24-hr exposures. Eurasian watermilfoil control was established in the 1.0 mg ae/l for 48 hr, and 2.0 mg ae/l for 36-hr, and 48-hr exposures. Control can be predicted for Eurasian watermilfoil treatments in both dynamic and static aquatic environments when plants remain in contact with 2,4-D concentrations greater than the developed threshold levels. Aquatic plant control, Eurasian watermilfoil; Herbicides., Original contains color plates: All DTIC and NTIS reproductions will be in black and white.

Growth of the submersed macrophyte, Myriophyllum spictam L., was examined in nine solutions differing in major cation (Ca, Mg, Na, and K) and inorganic carbon C sub t levels. Growth experiments were conducted under two conditions differing in the relative magnitudes of gas exchange and solution volume. Under conditions of limited solution volume, growth was adversely affected by the combination of low cation (particularly Ca) and low C sub t levels. However, where solution volume was greater, there was no effect of cations. Irrespective of volume, growth was increased by increasing C sub t from 3.5 to 10.5 mg/l, but was unaffected by further increase in C sub t to 21.00 mg/l. Photosynthetic uptake of C sub t during growth reduced levels of C sub t and acidity and increased pH. Alkalinity and Ca levels were also reduced in some solutions due to the precipitation of CaCO3. Diurnal analyses indicated C sub t was not appreciably replenished during the night; thus, the experimental systems continually lost C sub t throughout the study. Initial photosynthesis rates, measured in the same solutions, indicated a strong relationship between photosynthesic and solution C sub t. Measurements of the exchange of CO2 between the atmosphere and the solution during the photosynthesis experiments revealed the potential importance of the atmosphere as a significant source of carbon. Keywords: Aquatic plants; Eurasion watermilfoil; Water chemistry.

This design memorandum recommends a plan for the control of Eurasian watermilfoil, a nonnative aquatic plant, in the waters of Washington State. The plan was developed in response to a request from the State of Washington. Milfoil is presently a problem in several lakes, rivers, and reservoirs in eastern Washington and the Puget Sound area in western Washington. It has curtailed recreation activities in these areas and has the potential of decreasing water quality and impacting hydropower production, fish and wildlife, irrigated agriculture, and public health. In 1978, there were approximately 1,500 acres of navigable and nonnavigable waters with milfoil growth throughout the state. It is estimated that 113,000 acres of navigable waters could become infested within the next 15 years. The recommended plan consists of methods of prevention and control outlined in the report.

This report presents the results of the evaluation of two species of insects for the biological control of Eurasian watermilfoil (Myriophyllum spicatum L.). One of the species is a native weevil, Litodactylus leucogaster (Marsh.), which attacks the flower spikes, and the other is an accidentally introduced European moth, Acentria nivea (Oliver), whose larvae feed on the leaves and stems. The biology of L. leucogaster was studied in detail and host-specificity tests were conducted with adults and larvae. Since it was determined to be specific to watermilfoils, it was released at Crystal River, Florida, on 22 August 1979. Two adults were captured at Crystal River in November indicating possible establishment. The pyralid moth, A. nivea, was difficult to rear in the laboratory. Since the females were active only one night, successful matings were rare in the small colony. Larval production was best in containers that were minimally disturbed. the larvae required water temperatures below 22 C for development though they could survive short periods at higher temperatures. The larvae were not specific to milfoil; however, A. nivea may still be of interest as a member of a complex of species which attack milfoil. (Author)

The 13th Annual Meeting of the U. S. Army Corps of Engineers Aquatic Plant Control Research Program was held at Seattle, Washington, on 16-19 October 1978, to review current research activities and to afford an opportunity for presentation of operational needs. (Author)

The 12th Annual Meeting on the U. S. Army Corps of Engineers Aquatic Plant Control Research Program was held in New Orleans, La., on 3-7 October 1977 to review current operations activities and to afford an opportunity for presentation of current research projects. (Author)

Continued and accumulated studies on eurasian watermilfoil (Myriophyllum spicatum) and its relation to native submersed species in the upper Chesapeake Bay reveal that a pattern of change is taking place that has occurred before. These cyclic series of changes are triggered by vigorous ecological upheavals due to widespread prolonged turbidity from late spring into midsummer. Severe shorter term upheavals also occur, such as the widespread loss of submersed plants during late July and August 1969 over much of the Eastern Shore. The turbidity is the result of "wash-in" of soil caused by excessive and continued precipitation. This turbidity prevents light penetration in the water that is essential for growth of submersed plants. The overall result has been a kill-back of submersed vegetation to remnant and "pocket-type" existence.