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Title: Plant growth regulators as potential tools in aquatic plant management : efficacy and persistence in small-scale tests
Authors: Lembi, Carole A.
Chand, Tara
Keywords: Amidochlor
Aquatic plants
Bensulfuron methyl
Environmental persistence
Eurasian watermilfoil
Gas chromatography
Plant growth regulator
Aquatic plant control
Aquatic Plant Control Research Program (U.S.)
Publisher: U.S. Army Engineer Waterways Experiment Station
Series/Report no.: Contract Report (Aquatic Plant Control Research Program (U.S.)) ; no.Contract Report A-94-1
Abstract: Bioassay and small-scale test systems were used to determine the efficacy and persistence of plant growth regulators with potential for aquatic plant management. The goal of the project was to identify compounds that reduce plant height and thus weediness of the submersed flowering plants hydrilla (Hydrilla verticillata Royle) and Eurasian watermilfoil (Myriophyllum spicatum L.). Laboratory bioassays indicated that triclopyr and imazapyr were herbicidal rather than growth regulatory on these species. Bensulfuron-methyl and amidochlor showed growth regulatory properties on Eurasian watermilfoil, and further research may be warranted on these compounds. A number of studies were conducted on flurprimidol, a gibberellin synthesis inhibitor which reduces stem internode length, thereby effectively reducing vertical stem length. Two-hour exposures to flurprimidol significantly reduced vertical stem length at concentrations of 750 μg L⁻¹ for hydrilla and 200 μg L⁻¹ for Eurasian watermilfoil for at least 28 days post-treatment, suggesting that short-term exposures may be efficacious under certain circumstances. Flurprimidol was less effective at reducing stem lengths under low light intensities (4-18 μE m⁻² sec⁻¹) than under high light (800-1000 μE m⁻² sec⁻¹), but stem lengths were shorter under low light than in the untreated controls. As the plants reach the more well-lit portions of the water column, vertical growth should be reduced if flurprimidol is still present at physiologically active concentrations. Additional plants that were affected by flurprimidol included waterstargrass (Heteranthera dubia), slender naiad (Najas flexilis) , elodea (Elodea canadensis), and leafy pondweed (Potamogeton foliosus). Total plant lengths in Vallisneria americana and coontail (Ceratophyllum demersum) were not significantly affected by flurprimidol. Gas chromatographic procedures for detecting flurprimidol residues in water, plant tissues, and soil were developed. Flurprimidol dissipated rapidly from water (8.4 to 9.8 day half-life) and plant tissue (8.8 to 9.1 day half-life) and slowly from the soil (178 day half-life). Further studies are needed to determine the potential for long-term plant control, with emphasis placed on determining whether uptake of flurprimidol is from the water or hydrosoil. Our studies to date suggest that the gibberellin synthesis inhibitors provide a viable alternative as an aquatic plant management strategy.
Description: Contract Report
Gov't Doc #: Contract Report A-94-1
Rights: Approved for public release; distribution is unlimited
Appears in Collections:Contract Report

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