2011 Annual Report
1a.Objectives (from AD-416)
1) Improve our biological understanding and enhance our ability to manage important invasive weeds in western aquatic and riparian ecosystems..
2)Develop integrated vegetation management strategies to restore ecological structure and function to western aquatic and riparian ecosystems..
3) Determine the most ecologically sound and cost effective methods for managing aquatic and riparian weeds using herbicides and/or natural products..
4)Develop rapid response strategies and methods for aquatic plant infestations that pose serious economic and environmental threats.
1b.Approach (from AD-416)
1) A demographic study will determine how temporal and spatial variation in factors affecting Uruguayan water primrose contribute to overall population dynamics and improved management and restoration at Lagun de Santa Rosa. .
2)Egeria Carbon Hydrogen Nitrogen (CHN) and associated insect communities will be determined monthly at invaded/ non-invaded sites at in the Sacramento/San Joaquin Delta using presence/absence and hydroacoustical and videographic methods. .
3)Eurasian watermilfoil will be sampled (weekly to monthly) in the Truckee and Fall Rivers along streamflow gradients. .
4)Effects of simulated herbivory on Giant reed and effects on root growth (abundance, life span) will be quantified from images recorded with a video camera system within the minirhizotrons at weekly intervals. Success of active (planting desirable species) versus passive (recruitment from resident propagules) re-vegetation will be assessed in giant reed managed sites. 5)Effects of native and non-native submersed plants on rhizosphere microflora will be assessed in replicated mesocosms and natural populations. .
6)Replicated applications of fluridone, copper will be made in water and with penoxsulam, or acetic acid to canals and canal sediment. .
7)Methods to eradicate Curlyleaf pondweed will be evaluated in indoor and outdoor tanks using diquat, endothall, and penoxsulam under short and long-day conditions.
NOTE: This Project terminated in April, 2011 and some components were migrated, in part, to the new Project (5325-22000-026-00D).
During the period of this project progress has been made on understanding growth requirements, dispersal characteristics, and on the development of strategies for control of several invasive aquatic weeds including: Giant reed, Primrose- willows, Brazilian waterweed, hydrilla, yellow starthistle, and Eurasian watermilfoil. Field-scale studies aimed at improving aquatic weed control were successfully conducted in several weed-impacted ecosystems including: Lake Tahoe (CA, NV), the Sacramento-San Joaquin Delta, Fall River (CA), San Francisco baylands, San Joaquin River (CA), flood-control systems in Santa Rosa (CA), and several irrigation systems in CA, NV, ID. As part of these ecosystem-level projects, stakeholder partnerships and research collaborators were established to ensure appropriate focus of research objectives and to optimize resources. The impact and potential cultural-based control of algae in rice production systems was examined and new approaches to nutrient inputs were developed to minimize effects of algae growth. Collaborative investigations were conducted in Brazil, and Argentina for potential biological control agents for Brazilian waterweed and Primrose-willows were initiated and one herbivorous insect was identified and subjected to extensive host-specificity testing. Other biological control research on Eurasian watermilfoil was initiated using newly documented California populations of native weevils in collaboration with the California Department of Food and Agriculture (CDFA). Potential rapid response methods were examined to stop the spread of a non-native, invasive marine seaweed (Undaria) in San Francisco Bay. Efficacy of several herbicides were investigated for their potential use in management of aquatic and riparian weeds including: imazapyr, triclopyr, glyphosate, penoxsulam, fluridone, acetic acid, imazamox, and 2,4-D.
Transition to new Project: In April 2011, resources from this terminating project were re-allocated to a new 5-year project: (5325-22000-026-00D)- Title: AQUATIC AND RIPARIAN WEED MANAGEMENT TO PROTECT U.S. WATER RESOURCES IN THE FAR WEST UNITED STATES. New project subobjectives and associated hypotheses and protocols were developing by building upon progress and accomplishment made during the prior 5 years and through stakeholder input on research priorities. The new project emphasizes both individual weed species focus as well as ecosystem and landscape scale focus through specific collaboration of scientist within EWIR that are conducting research within another new project (5325-22000-024-00D): Title: LANDSCAPE-LEVEL ASSESSMENT AND MANAGEMENT OF INVASIVE WEEDS AND THEIR IMPACTS IN AGRICULTURAL AND NATURAL SYSTEMS.
Important components of the new project include: remote sensing, multi-species, fully integrated weed control objectives and follow-up research components to develop effective tools for rapid response methods to stop new invasive weeds and those with incipient, low-level distributions in freshwater, riparian and marine systems.
Management of Brazilian waterweed. Over 8,000 acres in the Sacramento-San Joaquin Delta are infested with invasive submersed aquatic plants that impair a range of ecosystem services including commercial navigation, transport of potable and irrigation water, and habitat for native species. This impacts commercial uses of the Delta and transfer of water to over 25 million Californian's in Southern California. ARS scientists at Davis, CA, in collaborative research with California Department of Boating and Waterways, Department of Water Resources, and formal Section 7 Consultation with NOAA- Fisheries (NMFS) and US Fish and Wildlife Service resulted in reduction in stands of Brazilian waterweed and Eurasian watermilfoil in 3,500 acres by over 80% over the past 5 years contributing to ecosystem health.
Biology and management of water primrose- willows (invasive Ludwigia species). Invasive species of Ludwigia have spread widely in flood control systems, irrigation systems and open natural aquatic sites in California where they impair safe water drainage, interfere with mosquito control operations and displace native riparian vegetation. ARS scientists at Davis, CA, performed studies at the field, mesocosm and laboratory scale to clarify the taxonomy of Ludwigia species and identified characteristics that promote reproduction, dispersal and invasions into sensitive wetlands. Dispersal floating seed-pods and germination of seeds were shown to be an important cause of rapid spread of this non-native plant. Control methods that can reduce fruit and seed production should be effective in reducing continued expansion. This new knowledge provides a basis for integrated management and will help direct searches for and evaluations of potential biological control agents from South American populations of these species.
Management of aquatic weeds in irrigation systems. Native and non-native weeds impede storage and conveyance of irrigation water that is essential for more than 75 percent of western state agricultural production. Controlling these weeds in flowing canal water is difficult using standard herbicide injections because the active ingredients are rapidly diluted and move away from target weeds. ARS scientists in Davis, CA, developed approved methods (tools) to place herbicides onto canal bottom sediments when canals are seasonally drained ("drawdown"), applications are better localized and more effective. The efficacy of acetic acid (vinegar) and “drawdown” (dry-canal) application of fluridone herbicide has provided two new tools to control weeds in conveyance systems. This cooperative research with irrigation districts and private registrants has led to changes in Federal and California Environmental Protection Agency (EPA) labeling that permits use of fluridone in de-watered irrigation canals conditions, which provides more localized control while reducing the potential for off-site movement of herbicide residues when canals are re-charged for use.
Eradication of an invasive marine alga. Marine systems are impacted by a variety of non-native invasive species that can affect fisheries, aquaculture and native species habitat. An invasive marine seaweed, Caulerpa (“Killer Algae”) was discovered for the first time in the Western Hemisphere in San Diego, CA, and threatened to spread to hundreds of miles of coastal environments as it has in the Mediterranean areas. Supporting research and technology transfer by ARS scientists in Davis, CA, as part of a multiagency consortium, helped lead to the successful, complete eradication of Caulerpa in California over a 6 year period. This project has served as a model for rapid response actions and stakeholder participation in extremely sensitive environments.
Algae control in rice. Excessive growth of algae can greatly reduce successful establishment of rice in California where it is seeded by air. Excessive growth algae impair proper emergence of rice seedlings by "smothering" new growth and preventing adequate light needed to produce healthy, dense rice crops. Careful examination of the typical fertilizer practices and their impact on early season algae growth by ARS scientists at Davis, CA, demonstrated that excessive nitrogen addition contributed significantly to algae-related problems while not necessarily improving crop yield. Results from this research have led to changes in cultural practices that have diminished the detrimental impact of algae during the early post-seeding rice-establishment stages.
Control of Arundo (Giant reed). Arundo donax, is a perennial invasive grass that spreads in the US exclusively by vegetative means and has invaded and altered many riparian ecosystems in the western U.S. Detailed growth models for giant reed were developed by ARS scientists at Davis, CA, by analysis of canopy structure and through use of spatial digitizing methods. This type of model can help identify phases of growth that may be susceptible to biological control. Measurements of leaf penetrability were made to help evaluate potential for leaf-feed insects. Field studies led to determining optimal timing for herbicide applications to maximize efficacy. Managing this invasive weed will improve riparian ecosystems.
Anderson, L.W. 2011. Introduced aquatic plants and algae. Encyclopedia of Introduced Invasive Species. 248-257.