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

Location: Invasive Species and Pollinator Health

2016 Annual Report

1a. Objectives (from AD-416):
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.

1b. Approach (from AD-416):
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.

3. Progress Report:
This report presents progress made on both objectives and their subobjectives of Project 2030-22000-030-00D, Enhancing Water Resources Stewardship through Aquatic and Riparian Weed Management, which was initiated in December 2015, and develops new lines of research from the previous Project 2030-22000-028-00D, Aquatic and Riparian Weed Management to Protect U.S. Water Resources in the Far West United States. Submersed invasive aquatic plants demonstrate a remarkable adaptability and plasticity to exploit novel environments under changing environmental conditions. In support of Objective 1, USDA scientists have identified locations in the Sacramento/San Joaquin River of California or Idaho (in the case of Hippuris vulgaris) to obtain most of the target native (Elodea canadensis, Hippuris vulgaris) and nonnative (Myriophyllum spicatum, Cabomba caroliniana, Hydrilla verticillata) species for photosynthesis studies and nutrient level response studies. USDA scientists have also identified potential sites in streams, lakes, and estuarine habitats for phenological studies of Potamogeton crispus. We have also collected populations of monoecious and dioecious hydrilla, egeria, and elodea for photosynthesis studies, and established cultures for future use in these studies. Appropriate permits have been obtained for hydrilla collections. Research was initiated to evaluate the influence of climate change and sea level rise of the growth and potential spread of native and invasive Spartina (cordgrass) species in Pacific west coast estuaries. Population sites were evaluated in the San Francisco Estuary and along the California coast. Rhizomes of native and exotic Spartina species were collected at study sites in San Francisco Estuary, and live plant cultures are being maintained for experimental use. Under permit from the State of California and agreements with the pertinent states, flowering rush (Butomus umbellatus) was collected from the Lower Clark Fork River system (Montana), Detroit Lakes (Minnesota), and adjacent to the Snake River (Idaho), and established in mesocosms at the USDA ARS facility in Davis, California. Plant performance is being measured weekly on a subset of plants from each population. Pots have been harvested from replicated mesocosms for each population every month, and assessed for biomass of leaves, inflorescences, and rhizomes. Rhizome bud density is counted for each harvest, as well. A weather station and temperature datasondes were established on the site to collect a continuous measure of air and water temperature. The U.S. Army Engineer Research and Development Center is collaborating with USDA scientists at Davis, California in this research. USDA scientists have identified sources of water hyacinth, South American spongeplant, and water primrose for temperature and nutrient response studies. A greenhouse tank facility with controlled water temperature is being completed for use in the temperature studies at the Davis, California aquatic weed research laboratory. As yet, permit applications have not received approval for South American spongeplant studies. In support of Objective 2, USDA scientists from Davis, California have selected three sites on the Sacramento/San Joaquin River Delta (California) for curlyleaf pondweed and egeria, and are being sampled monthly. Temperature-recording datasondes were deployed at these sites to collect both air and water temperature, in support of assessing seasonal growth. Phenological indicators such as flowering, peak growth, and propagule formation will be used from these studies to evaluate strategies for improved management in the Delta, and elsewhere. Working with the U.S. Army Engineer Research and Development Center, USDA scientists from Davis, California have established three sample sites for flowering rush phenology in Idaho and Montana. At these sites, temperature datasondes have been deployed to measure air and water temperature. Samples have been collected in spring and early summer, with collections planned for late summer and fall. Plant growth and phenology will be compared to the common garden experiment in Davis, California for response to temperature and initiation of growth. Studies were initiated to examine the toxicity of four aquatic herbicides (2,4-D, glyphosate, penoxsulam and imazamox) and two adjuvants varying in chemical composition to the water hyacinth planthopper. Groups of ten planthoppers were exposed to individual leaves treated with one of the herbicides or surfactants. Results from these studies will assist in developing recommendations compatible with integrated plant management (IPM) approaches, to maximize the benefit of biological control when combined with the use of herbicides. USDA scientists, working in collaboration with NASA, UC-Davis, and California State Parks, have completed two trials on water hyacinth. In the first trial, we evaluated the efficacy of four surfactants on water hyacinth control with glyphosate. One surfactant provided significantly better control than the other three. In the second trial, three herbicides (glyphosate, penoxsulam, and imazamox) were evaluated for control of water hyacinth in the greenhouse experiment. During the experiment, hyperspectral reflectance was recorded to evaluate if ultimate efficacy could be predicted from reflectance after treatment, and remote sensing be used as a possible tool to follow herbicide treatment success in the field. Scientists have set up two more trials this year, with results in the fall of 2016. In the first new trial, water hyacinth treatment with two rates of glyphosate, imazamox, penoxsulam, and 2,4-D are being treated, with the goal of comparing the efficacy of the new herbicides imazamox and penoxsulam to the standard treatments of glyphosate or 2,4-D. In the second new trial, ARS scientists at Davis, California will be evaluating ten herbicides for their effectiveness for control of egeria in mesocosm tank studies. The herbicides to be tested are bispyribac sodium, carfentrazone-ethyl, complexed copper, diquat, both the potassium salt and amine formulations of endothall, flumioxazin, fluridone, imazamox, and penoxsulam. This trial will be the first third-party trials performed for several of these herbicides with the invasive aquatic weed Egeria densa. We have initiated evaluation of Ludwigia invasions in five major watershed regions of Florida: Kissimmee Chain of Lakes, Alligator Chain of Lakes, lower Kissimmee River, Lake Okeechobee, and St John’s River. A permit was obtained for import of live plant tissue from Florida to the ARS lab in Davis, California. Florida population sites were each divided into five subareas, and extensive sampling of live plant tissue and dried voucher specimens was completed. Morphological, cytological and genetic evaluation of plant tissue from Florida is in progress for comparison with specimens from invaded populations in California, and from Argentina and Uruguay in the native range. Significant progress has been made towards clarifying taxonomic and genotypic identity of invasive Ludwigia taxa. These data are crucial support for development of integrated management strategies and evaluation of potential biological control agents. In addition to chemical and mechanical control options, ARS scientists are investigating the use of insects to aid in the suppression of invasive Ludwigia species. Insects that feed on and damage only the target weed but don’t effect the fitness of non-target plants in the environment may be very useful tools for holistically controlling Ludwigia in the United States. One candidate insect that may serve as a “biological control agent” is a very small thrips (Liothrips) native to Argentina. Unfortunately, collaborators in Argentina were unable to secure an export permit for the candidate biological control agent. Progress on this front is limited until Argentine regulators approve the export to the U.S. of the insect for use in research. In the meantime, ARS scientists are working with scientists in Uruguay to acquire export permits for insects native to their country but considered problematic weeds in the Western U.S. The environmental safety of Argentinian fly Hydrellia egeriae as a biological control agent of Egeria densa in the western U.S. was determined. Because previous researchers indicated that the fly may feed on non-target Elodea spp., our host specificity tests focused on Elodea canadensis, a native plant that has a widespread distribution in North America. Experiments were conducted by presenting flies the target weed or the non-target plant singly or in combination. In the no-choice test, the number of eggs laid were similar on Egeria and Elodea. In the choice tests, more eggs were laid on Egeria, although 13% of total eggs were still laid on Elodea. A 3rd test measured the suitability of both plants for fly development: survival was 72% on Egeria compared with 44% on Elodea. A Final test showed that there was no difference in egg production between the flies on the two plants, indicating that H. egeriae might be able to attack Elodea and establish in the field if it were released. Our findings indicate that the host range of the fly H. egeriae is too broad for use as a biological control agent and further resources dedicated to the development of this insect is unwarranted.

4. Accomplishments

5. Significant Activities that Support Special Target Populations:

Review Publications
Madsen, J.D., Wersal, R.M. 2015. Evaluation of six herbicides for control of swamp smartweed [Persicaria hydropiperoides (Michx.) Small] under flooded and moist soil conditions. Journal of Aquatic Plant Management. 53:224-227.

Madsen, J.D., Turnage, G., Getsinger, K.D. 2016. Efficacy of combinations of diquat or triclopyr with fluridone for control of flowering rush. Journal of Aquatic Plant Management. 54(2):68-71.

Madsen, J.D., Sartain, B., Turnage, G., Marko, M.D. 2016. Management of flowering rush in the Detroit Lakes, Minnesota. Journal of Aquatic Plant Management. 54(2):61-67.

Duffy, W.G., Garone, P., Grewell, B.J., Kahara, S.N., Fleskes, J., Helm, B., Moyle, P.B., Records, R., Silveira, J. 2016. Wetlands. In: Mooney, H. and Zavaleta, E., editors. Ecosystems of California: A Source Book. Berkeley, CA: University of California Press. p. 669-692.