The Hydrilla Task Force has been asked if fluridone builds up in the bottom sediment. A study in one climate and situation may not be entirely applicable to the Cayuga Inlet, however some studies have been done.
Anyone interested may want to read the following articles in full.
Finding of Interest: Environmental sampling found fluridone present at extremely low levels in native marsh plants, water, and sediment
Citation: Monheit, S., Leavitt, R., Akers, P., & Wong, E. (January 01, 2008). Health Hazard Assessment for Native Americans Exposed to the Herbicide Fluridone via the Ingestion of Tules at Clear Lake, California, USA. Human and Ecological Risk Assessment: an International Journal, 14, 5, 1056-1069.
Website: http://www.ingentaconnect.com/content/tandf/bher/2008/00000014/00000005/art00011
Abstract: This study addresses concerns expressed by Native Americans regarding exposure via the consumption of aquatic vegetation to the herbicide fluridone (active ingredient) used by the California Department of Food and Agriculture (CDFA) Hydrilla Eradication Program in Clear Lake, California. In 2005, the Department monitored lakeshore vegetation, water, and sediment at four locations, before and after seasonal applications of fluridone. Subchronic and chronic exposures were evaluated, and hazard quotients calculated for a worst-case exposure (WCE) scenario. Ingestion rates and other exposure factors were developed in public meetings with tribal members. Environmental sampling found fluridone present at extremely low levels in tule vegetation, water, and sediment. Exposures were four times greater in subchronic timeframes than chronic timeframes; however, hazards were less due to the 25-fold larger reference dose (RfD) used for subchronic calculations: RfD(subchronic) = 2.0 mg/kg-day, RfD(chronic) = 0.08 mg/kg-day. Conservative, child, total daily ingestion (TDI) doses were calculated to be 8.3 × 10-5 mg/kg-day (subchronic) and 2.1 × 10-5 mg/kg-day (chronic). Hazard quotients (HQ) for subchronic and chronic exposures were on the order of 10-5 and 10-4, respectively, indicating that at current application regimes, there is little to no hazard of adverse effects from fluridone exposure via ingesting Clear Lake tules.
Finding of interest: The half-life of fluridone in sediment was 12 months under laboratory conditions (25 "C) and about 17 weeks under field conditions.
Citation: Muir, D. C. G., & Grift, N. P. (1982). Fate of fluridone in sediment and water in laboratory and field experiments. Journal of Agriculture and Food Chemistry, 30(2), 238-244. doi: 10.1021/jf00110a006
Website: http://pubs.acs.org/doi/abs/10.1021/jf00110a006
Abstract: The fate of the aquatic herbicide fluridone [ l-methyl-3-phenyl-5-[ (3-trifluoromethyl)phenylj-4( 1H)- pyridinone] was studied in sediment-water systems in culture flasks, in pond water exposed to sunlight, and in small ponds by using either a carbonylJ4C- or N-meth~l-l~C-labeled compound. The half-life of fluridone in sediment was 12 months under laboratory conditions (25 "C) and about 17 weeks under field conditions. In the laboratory study, the major degradation product of fluridone in sediment was fluridone-acid [ l,4-dihydro-l-methyl-Coxo-5- [3-(trifluoromethyl)phenyl]-3-pyridinecarboxylic acid; 111. I1 accounted for 48-54% of the radioactivity that was extracted from sediments incubated for a 26-month period. Two phenolic compounds, 4-hydroxyfluridone [ l-methyl-3-(4-hydroxyphenyl)-5-[3-(trifluoro- methyl)phenyl]-4(1H) pyridinone; 1111 and the 2-hydroxy derivative (V), were identified as minor breakdown products of fluridone in sediment (0.5-2.5 % of radioactivity). Desphenylfluridone [ 1- methyl-3-[3-(trifluoromethyl)phenyl]-4( 1H)-pyridinone; I], 11, 111, and V were identified in aqueous solutions of fluridone held in Pyrex flasks in sunlight. The half-life of fluridone in ponds treated at 100 pg/L was 2-3.5 days, and I11 and V were identified at low levels (0.05-0.5pg/L) in water sample extracts. No major degradation products of fluridone were identified under field conditions due to the apparent extensive photodegradation of the compound.
Finding of Interest: Fluridone dissipated with an average half-life of 20 days in pond water and 3 months in pond hydrosoil.
Citation: West, S. D., Burger, R. O., Poole, G. M., & Mowrey, D. H. (1983). Bioconcentration and field dissipation of the aquatic herbicide fluridone and its degradation products in aquatic environments. Journal of Agriculture and Food Chemistry, 31(3), 579-585. doi: 10.1021/jf00117a028
Website: http://pubs.acs.org/doi/pdf/10.1021/jf00117a028
Abstract: The accumulation and dissipation patterns of the aquatic herbicide fluridone, l-methyl-3-phenyl-5- [3-(trifluoromethyl)phenyl]-4( 1H)-pyridinone, and its major degradation products have been determined in 40 pond and lake experiments in the United States, Panama, and Canada. The average biocon- centration factor for the total residue of fluridone plus a single major metabolite, l-methyl-3-(4- hydroxyphenyl)-5-[3-(trifluoromethyl)phenyl]-4(1H)-pyridinone, in several fish species was 1.33, 7.38, and 6.08 in edible tissue, inedible tissue, and whole body, respectively. Fluridone dissipated with an average half-life of 20 days in pond water and 3 months in pond hydrosoil. The treatment of small areas (0.8-4.0 ha) of large lakes resulted in more rapid dissipation due to dispersal of fluridone into the surrounding untreated water. Little or no carry-over of residues occurred prior to annual retreatments of the ponds. Mathematical models were evaluated for relating the half-life of fluridone in pond water to physical and chemical properties of the water.
Finding of interest: Fluridone residues were detected in the hydrosoil immediately following treatments and generally peaked coinciding with the decline in aquatic plant biomass. The maximum fluridone detected in the hydrosoil was only 5% of the 2.25 kg ha-1 applied, and this amount was obtained from outside of a treatment area. Residue concentrations were highly variable between sampling sites and sampling periods and unexpectedly increased 14 months after treatment. Winter-killed marginal vegetation is a possible source of this increase
Citation: Schmitz, D. C., Leslie, A. J., Nall, L. E., & Osborne, J. A. (1987). Hydrosoil residues and hydrilla verticillata control in a central florida lake using fluridone. Pest Management Science, 21(1), 73-82. doi: 10.1002/ps.2780210108
Website: http://onlinelibrary.wiley.com/doi/10.1002/ps.2780210108/abstract
Abstract: Fluridone was applied to a 98-8-ha lake in Orange County, Florida, USA, in five different treatment plots between October 1982 and February 1983 to control a severe infestation of Hydrilla verticillata. Hydrosoil residues and submersed aquatic plant biomass were monitored within the lake. Fluridone did not affect the submersed vegetation during the 4-month fall-winter treatment period. As water temperatures increased during spring, Hydrilla biomass declined at an average of 0.178 kg m-2 per month. By summer (192 days after last treatment), the target species could not be found within the lake. Fluridone residues were detected in the hydrosoil immediately following treatments and generally peaked coinciding with the decline in aquatic plant biomass. The maximum fluridone detected in the hydrosoil was only 5% of the 2.25 kg ha-1 applied, and this amount was obtained from outside of a treatment area. Residue concentrations were highly variable between sampling sites and sampling periods and unexpectedly increased 14 months after treatment. Winter-killed marginal vegetation is a possible source of this increase. Detectable concentrations of fluridone, and vegetation control, persisted for a total of 86 weeks from the date of the last treatment and non-detectable residues may have persisted after 86 weeks. This study indicates that a lower application rate might have provided adequate control of Hydrilla and possibly decreased residue concentrations in non-target areas.
Finding of interest: Fluridone persisted for less than 365 days in all of five tested soils in Georgia. After reapplication, the persistence was even shorter.
Citation: Schroeder, J., & Banks, P. A. (July 01, 1986). Persistence of Fluridone in Five Georgia Soils. Weed Science, 34, 4, 612-616.
Abstract: Field research was conducted in 1982 and 1983 to characterize the persistence of fluridone {1-methyl-3-phenyl-5-[3-(trifluoromethyl)phenyl]-4(1H)pyridinone} in five Georgia soils. Fluridone persisted less than 365 days in all soils, with shorter persistence upon reapplication in 1983 which indicated the potential for enhanced microbial degradation. A significantly higher rate of loss in 1983 compared to 1982 was recorded in the Greenville sandy clay and Dothan loamy sand soils. A higher rate of loss was recorded for the 1.7 kg ai/ha than the 0.6 kg/ha treatment in the Bradson clay loam and Rome gravelly clay loam soils. No grain sorghum [Sorghum bicolor (L.) Moench. 'BR 64') injury was observed in a field bioassay planted in the spring of 1984. Herbicide leaching did not appear to be an important method of loss.
Finding of Interest: Low levels of Fluridone were found in clay 250 days after treatment, and up to 25% remained in fine sandy loam 385 days after treatment. Fluridone degradation was also found to be faster in the field than under controlled conditions.
Citation: Banks, P. A., Ketchersid, M. L., & Merkle, M. G. (November 01, 1979). The Persistence of Fluridone in Various Soils under Field and Controlled Conditions. Weed Science, 27, 6, 631-633.
Abstract: The concentration of fluridone {1-methyl-3-phenyl-5-[3-(trifluoromethyl)phenyl]-4(1H)-pyridinone} residue in Miller clay and Lufkin fine sandy loam was determined at various intervals following incorporated and nonincorporated applications in the field. Low levels of fluridone were present in Miller clay after 250 days while up to 25% remained in Lufkin fine sandy loam 385 days after treatment. Incorporation of fluridone increased its persistence in Lufkin fine sandy loam but not in Miller clay. Fluridone degradation in Miller clay and Lufkin fine sandy loam was more rapid in the field than under controlled conditions. Fluridone degradation in sterilized Brennan fine sandy loam and Hidalgo sandy clay loam was significantly slower than in nonsterilized soil kept under the same conditions. These differences were not observed in Lufkin fine sandy loam and Miller clay.
Citation: Banks, P. A., & Merkle, M. G. (May 01, 1979). Soil Detection and Mobility of Fluridone. Weed Science, 27, 3, 309-312.
Abstract: Bioassay and gas chromatographic procedures were evaluated for their effectiveness in detecting fluridone [1-methyl-3-phenyl-5-[3-(trifluoromethyl)phenyl]-4(1H)-pyridinone] in soil. Bioassay procedures were limited to a detection range of 0.05 to 0.45 ppmw if grain sorghum (Sorghum bicolor (L.) Monech) was used. Visual estimations of chlorophyll content in affected plants, used as an indicator of fluridone concentration, were as reliable as spectrophotometric determinations. Gas-liquid chromatographic (GLC) procedures were less variable than the bioassay and had no upper limit of detection. Recovery of fluridone from treated soil ranged from 60 to 100 percent, depending on soil type. Soil water content affected percent recovery. Fluridone did not leach more than 1 cm in clay or sandy loam soils when up to 10 cm of water was passed through a soil column containing the herbicide, as determined by GLC. Extensive downward movement, 12 to 16 cm, occurred in a coarse sand when 5 or 10 cm of water was passed through the column.
Last updated December 14, 2016