title: Evaluation of propargyl bromide for control of barnyardgrass and Fusarium oxysporum in three soils.
abstract: With the scheduled phasing out of methyl bromide, there is an urgent need for alternatives. We evaluated the efficacy of propargyl bromide as a potential replacement for methyl bromide for the control of barnyardgrass (Echinochloa crus-galli) and Fusarium oxysporum in an Arlington sandy loam, a Carsitas loamy sand and a Florida muck soil. Soil was mixed with barnyardgrass seeds or F oxysporum colonized on millet seeds, and treated with propargyl bromide at a range of concentrations. The mortality of the fungi and weed seeds was determined after 24 h of exposure at 30 degrees C. The concentrations required to inhibit 50% barnyard seed germination (LC50) were 2.8, 2.4 and 48.5 micrograms g-1 in the sandy loam, loamy sand and muck soil, respectively. In contrast, the LC50 values for F oxysporum were 11.2, 10.8 and 182.1 micrograms g-1 in the sandy loam, loamy sand and muck soil, respectively. The low efficacy of propargyl bromide in the muck soil was a result of the rapid degradation and high adsorption of the compound in the soil. The degradation half-life (t1/2) was only 7 h in the muck soil at an initial concentration of 6.8 micrograms g-1, compared to 60 and 67 h in the sandy loam and loamy sand, respectively. The adsorption coefficients (Kd) were 0.96, 0.87 and 5.6 cm3 g-1 in the sandy loam, loamy sand and muck soil, respectively. These results suggest that registration agencies should consider site-specific properties in recommending application rates for propargyl bromide.
authors.affiliation: George E Brown Jr Salinity Laboratory, USDA-ARS, 450 West Big Springs Road, Riverside, CA 92507, USA.
authors.forename: Q
authors.initials: Q
authors.lastname: Ma
authors.forename: J
authors.initials: J
authors.lastname: Gan
authors.forename: J O
authors.initials: JO
authors.lastname: Becker
authors.forename: S K
authors.initials: SK
authors.lastname: Papiernik
authors.forename: S R
authors.initials: SR
authors.lastname: Yates
mesh_terms: D000327:Adsorption; D000465:Algorithms; D004305:Dose-Response Relationship, Drug; D005651:Fumigation; D005670:Fusarium / Q000187:drug effects / Q000378:metabolism*; D006842:Hydrocarbons, Brominated / Q000494:pharmacology; D008954:Models, Biological; D008897:Panicum / Q000187:drug effects / Q000378:metabolism*; D010575:Pesticides / Q000032:analysis* / Q000378:metabolism / Q000494:pharmacology; D012639:Seeds / Q000187:drug effects / Q000378:metabolism; D012987:Soil / Q000032:analysis*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*
chemical_list: D006842:Hydrocarbons, Brominated; D010575:Pesticides; D012987:Soil; D012989:Soil Pollutants; C005218:methyl bromide