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United States Department of Agriculture

Agricultural Research Service

Research Project: Enhancing Water Resources Stewardship through Aquatic and Riparian Weed Management

Location: Exotic and Invasive Weeds Research

Project Number: 2030-22000-030-00-D
Project Type: In-House Appropriated

Start Date: Dec 15, 2015
End Date: Dec 14, 2020

Objective:
The long-term objective of this project is to develop and enhance integrated plant management approaches for invasive aquatic plants significant to U.S. Pacific West watersheds. This will be accomplished by developing a better understanding of weed biology and ecology, and the application of multiple management techniques on target invasive plants. Specifically, during the next five years we will focus on the following objectives: Objective 1: Determine the effects of specific environmental parameters (i.e., carbon dioxide concentration, temperature, light, hydroperiod, sediment nutrient levels, and salinity) on aquatic plant growth for key invasive weeds of the Pacific West watersheds. Subobjective 1A. Determine the relative importance of environmental drivers (e.g. light, temperature) controlling the growth or response to climate change of submersed invasive aquatic plant species. Subobjective 1B. Determining the environmental drivers influencing the growth of emergent and floating aquatic plant species. Objective 2: Develop environmentally safe, yet effective, integrated weed management approaches for aquatic and riparian weeds by identifying critical points in plant life histories to target, and by integrating biological, chemical, mechanical and cultural control strategies. Subobjective 2A. Phenology and life history considerations in long-term management of the invasive plants curlyleaf pondweed, egeria, and flowering rush. Subobjective 2B. Development and evaluation of integrated pest management techniques for invasive aquatic plants. Subobjective 2C. Evaluate the potential for biological control of invasive aquatic plant populations.

Approach:
1. Sediment fertility will be more significant for the growth of all submersed species; Eurasian watermilfoil (M. spicatum), curlyleaf pondweed (P. crispus), monoecious hydrilla (Hydrilla verticillata), egeria (Egeria densa), cabomba (C. caroliniana), and elodea ( Elodea canadensis) than water column fertility. The growth potential of rooted submersed macrophytes will be examined in outdoor tank experiments with a range of sediment and water column nutrients. 2. Dense mats of Eichhornia crassipes cause higher rates of phosphorus release from sediments than found in either native vegetation or unvegetated, open water areas, causing internal loading of phosphorus throughout the summer. This hypothesis will be tested by measuring levels of inorganic P, pH, DO, and temperature in the water column under water hyacinth mats and in adjacent stations with native floating or emergent plants, and open water stations free of water hyacinth at multiple sites in the Delta. 3. Interspecific differences in responses of invasive and native cordgrasses to inundation and salinity with rising sea level in Pacific Coast estuaries. In a full factorial experiment, we will cross 3 Spartina species (native S. foliosa, and alien S. densiflora, S. alterniflora) with 3 aqueous salinity levels (0,15,30 ppt) and 3 simulated tidal inundation treatments (25, 50 or 100% of a tidal cycle) for 27 treatment combinations replicated 6 times (n=162) in a randomized complete block design with all treatment types at each site (block). 4. Characterize the phenology of curlyleaf pondweed (Potamogeton crispus L.) and egeria (Egeria densa Planch.) in the Delta to identify long-term management endpoints and timing of management, and test the operational management program for meeting the goal of long-term plant reduction. In the first phase, the phenology of these two species will be studied over a two-year time period. In the second phase, potential improvements in management will be documented in operational treatments. 5. The planthopper Megamelus scutellaris will not show mortality after direct exposure to residues of 2,4-D, glyphosate, penoxsulam or imazamox, but will show mortality after exposure to nonionic crop oil based adjuvants. In mesocosms, populations of the planthopper on plants to which herbicides are applied will suffer little or no mortality and will establish populations on simulated recolonization plants. 6. Develop use patterns of recently labeled aquatic herbicides for control of water hyacinth and egeria in the Delta. We propose two series of experiments to evaluate new active ingredients that have been approved for aquatic use in California: imazamox, imazapyr, penoxsulam, byspyribac sodium, flumioxazin, topramezone, and carfentrazone. In the first series, water hyacinth control will be examined with foliar treatments of imazamox, imazapyr, penoxsulam, bispyribac sodium, flumioxazin, topramezone, triclopyr and carfentrazone. Treatments with 2,4-D and glyphosate will be added as the two current standard treatments. 7. Determine correct taxonomy of invasive Ludwigia in Florida, and compare with populations in California, Oregon and South America.

Last Modified: 06/24/2017
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