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Accepted manuscript

Response of four Vallisneria taxa to aquatic herbicides

Published online by Cambridge University Press:  29 October 2024

Jens P. Beets*
Affiliation:
Research Ecologist, US Department of Agriculture, Agricultural Research Service, Invasive Species and Pollinator Health Unit, Davis, CA, USA
Erika J. Haug
Affiliation:
Environmental Specialist, North Carolina Division of Water Resources, Intensive Surveys Branch, Raleigh, NC, USA
Benjamin P. Sperry
Affiliation:
Research Biologist, US Army Engineer Research & Development Center, Gainesville, FL, USA
Ryan A. Thum
Affiliation:
Professor, Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT, USA
Robert J. Richardson
Affiliation:
Professor, Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC, USA.
*
Author for correspondence: Jens Beets, Research Ecologist, US Department of Agriculture, Agricultural Research Service, 2705 Levee Road, Davis, CA 95616, USA; Email: [email protected]
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Abstract

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Native aquatic macrophytes such as Vallisneria americana Michx. are often desirable in aquatic ecosystems due to the ecological benefits they provide but are threatened by competition from invasive taxa including nonnative Vallisneria taxa and hydrilla (Hydrilla verticillata L.f. Royle). Identifying potential selective herbicide management options can provide options to minimize impacts to native taxa in restoration and aquatic invasive plant management programs. Greenhouse mesocosm experiments were conducted in 2023 to investigate herbicide efficacy on two native eelgrass species (V. americana and V. neotropicalis Vict.), two nonnative taxa (V. australis S.W.L. Jacobs & Les and V. spiralis × V. denseserrulata Makino) and H. verticillata. Herbicide applications included endothall, diquat, florpyrauxifen-benzyl, fluridone, and flumioxazin and select combinations of these herbicides used in H. verticillata management. Endothall alone provided 90 to 100% aboveground biomass reduction at 3000 µg L-1 with at least 24 hours of continuous or intermittent exposure to all native and invasive species at six weeks after exposure, whereas florpyrauxifen-benzyl applied alone resulted in minimal aboveground biomass reduction. A 45 day of exposure of fluridone (10 µg L-1) resulted in 95% biomass reduction on V. americana and 7 to 48% other tested taxa. The combination of flumioxazin and florpyrauxifen-benzyl resulted in 90 to 100% aboveground biomass reduction and endothall combined with florpyrauxifen-benzyl resulted in 93 to 100% aboveground biomass reduction across taxa. Reductions in belowground biomass mirrored trends observed in aboveground biomass. No treatments selectively controlled invasive Vallisneria without injury to native Vallisneria, although efficacy was observed on hydrilla. These insights provide an understanding for differences between these Vallisneria for researchers moving forward with selectively targeting H. verticillata in the presence of native Vallisneria species and two new aquatic invasive plants. Future research should expand treatment scenarios, increase the study period, and identify potential integrated plant management strategies for field scenarios.

Type
Research Article
Copyright
© Weed Science Society of America, 2024