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ARS Home Pacific West Area Albany, California Western Regional Research Center Invasive Species and Pollinator Health Research





- Grewell, Brenda
- Pratt, Paul
- Moran, Patrick
- Mueller, Rebecca
- 2023
- 2022
- 2021
- Publications
- Crop Protection & Quarantine (304)

Research Project: **Location:
                            Invasive Species and Pollinator Health** Project Number: 2030-22300-032-000-D
                        
                        Project Type: In-House Appropriated Start Date: Nov 30, 2020
                        
                        End Date: Nov 29, 2025 **Objective:**
                        
                        The long-term objective of this project is to develop and improve integrated weed management (IWM) and restoration strategies that successfully reduce the abundance of invasive aquatic and wetland weeds, to aid in the protection of water resources and improve environmental quality in aquatic and wetland ecosystems in far western states. This holistic approach, applied through an IWM framework, will increase the efficacy of weed management and reduce weed abundance to restore invasion-resistant vegetation and ecosystem services. Specific objectives to be addressed follow. 

Objective 1: Advance basic knowledge of weed biology and invasion ecology and develop improved integrated weed management (IWM) strategies in aquatic and wetland ecosystems. 

Sub-objective 1A: Determine the correct taxonomy, systematics and extent of hybridization of invasive weeds. 

Sub-objective 1B: Identify key biological and ecological processes influencing growth, invasiveness and IWM of aquatic and wetland weeds. 

Sub-objective 1C: Evaluate new herbicides and improve herbicide application techniques to enhance management efficacy of aquatic weed species. 

Objective 2: Evaluate the contributions of biological control on aquatic weed population dynamics through the lens of environmental variation, IWM, and ecosystem management. 

Sub-objective 2A: Evaluate biological, demographic and ecological factors that affect insect biological control agents, herbivory and weed abundance to improve efficacy of biological control. 

Sub-objective 2B: Evaluate impact of biological control of invasive wetland and riparian weeds in the context of integrated weed management. 

Objective 3: Develop ecological restoration implementation and monitoring strategies within an IWM framework to overcome invasive plant impacts and achieve restoration of plant communities and ecosystem services. 

Sub-objective 3A: Determine plant community and environmental characteristics that contribute to invasion resistance. **Approach:**
                        
                        To support Objective 1, field sampling and molecular tools will be used to confirm genotypes of native and alien Phragmites australis and hybrids to elucidate genetic identity and diagnostic morphological traits of invasive taxa specific to the Delta-Suisun Marsh. In a 2-year field study at 3 Delta study sites, we will evaluate phenological development, biomass production and growth rates of South American spongeplant monthly to determine optimal timing of management. In a greenhouse experiment, we will also assess growth of 5 invasive and 3 native aquatic weed species in response to 6 water temperatures to develop predictive models to identify optimal timing for herbicide application. We will field measure plant traits and acclimation of alligator weed along a tidal range and salinity gradient. In a greenhouse, we will evaluate salinity tolerance of alligator weed using 2 growth forms (floating, emergent) X 4 salinity levels X 6 replicates arranged in a nested random block design. Experimental screening tests of new herbicide active ingredients will be conducted under controlled conditions using a hood-enclosed spray table and jar trials. Effective herbicides will then be tested in large replicated outdoor mesocosm experiments to assess weed survival and biomass responses. Dye studies will be performed at replicated Delta sites with low, medium and high water residence times to determine efficacy, optimal concentrations and exposure times of new herbicides to improve management of submersed aquatic plant species. 

Under Objective 2, alligator weed biological control agents (A. hygrophila and A. andersoni) will be acquired from domestic and foreign sources. Experiments in controlled temperature incubators will elucidate critical minimum thermal limits and interspecific differences in cold tolerance to discover climatically-compatible biotypes for establishment, over-wintering, and efficacy for IWM in western watersheds. The effect of plant water availability on the establishment and impact of biological control for IWM of arundo will be studied. We hypothesize releases of arundo wasp and arundo armored scale will establish larger populations in release plots with integration of mechanical control than in plots with no pre-treatment. Pre-dawn water potential measurements of plant water status will be correlated with arundo wasp exit hole counts at 50 points across 3 sites. Colonization and impact of both insects on regrowth of arundo following herbicide application will be assessed. 

Under Objective 3, we will design revegetation techniques using biotic resistance in an IWM framework to overcome invasive water primrose impacts in wetlands. Plant community composition, species abundance, and environmental variables will be assessed in large replicated field plots. Indicator species analysis, trait–environment filter models, and experiments will be used to identify strongly persistent native plant species resistant to competitive displacement by the invader under varying environmental conditions. Results will provide a foundation for IWM using improved restoration techniques to reduce invader impacts.


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