Leaching Potential and Efficacy of Select Herbicides in Turfgrass Environments

Pesticide regulations based on environmental fate data collected from other agricultural systems may be inappropriate for an established turfgrass system. Field lysimetry experiments were conducted during 2007 -- 2009 to compare downward mobility of select herbicides in an established bermudagrass fairway and bare ground systems. Summer and winter applications were also compared. Evaluated herbicides included atrazine, mesotrione, monosodium methylarsonate, pendimethalin and sulfentrazone. Lysimeters were removed 60 or 120 d after initial treatment and analyzed for parent analyte or total arsenic (monosodium methylarsonate) content. Herbicides generally remained in vegetation or surface soil of a bermudagrass system whereas they distributed beyond the surface soil of a bare ground system. Herbicides likely remained in surface soil or vegetation of bermudagrass due to increased organic matter content. Additionally, greater herbicide concentrations were reported after winter applications, likely due to decreased biotic and abiotic degradation. These data confirm herbicide downward mobility varies among turfgrass and bare ground systems and may allow regulatory agencies to view pesticide fate among these systems independently. These data may also assist managers in devising comprehensive integrated pest management principles that may reduce adverse environmental effects.;Another series of experiments were conducted to determine the efficacy of select herbicides on common and troublesome perennial sedge species. Field experiments were conducted during 2007 and 2008 to evaluate herbicide treatment regimes for postemergent purple nutsedge and false-green kyllinga control. Sedge control varied among years likely due to reduced rainfall during 2007. During 2007, pooled across herbicide rate and number of applications, sulfosulfuron provided greater purple nutsedge control than trifloxysulfuron. Sulfosulfuron and trifloxysulfuron provided similar purple nutsedge control in 2008, although each were less effective compared to 2007. During 2007, sulfosulfuron and trifloxysulfuron provided excellent false-green kyllinga control, while trifloxysulfuron provided greater control compared to sulfosulfuron in 2008. Regardless of year, sulfentrazone provided < 30 and 60% purple nutsedge and false-green kyllinga control, respectively. Data from this research also indicates a sequential application enhances sedge control compared to a single application. Further, a sequential application 6 WAIT provided that greatest sedge control with evaluated herbicides. These data indicate sulfosulfuron or trifloxysulfuron may offer acceptable postemergent perennial sedge control in tolerant warm-season turfgrasses; however, sulfentrazone alone or tank-mixed with select herbicides did not provide acceptable sedge control. Greenhouse experiments were conducted to determine the effect of selective herbicide placement on false-green kyllinga, purple nutsedge, and yellow nutsedge shoot number, shoot weight and root weight. Selective herbicide placement levels included soil only, foliage only, and soil + foliage while evaluated herbicides included sulfentrazone, sulfosulfuron and trifloxysulfuron. Yellow nutsedge and false-green kyllinga were more sensitive to sulfentrazone, compared to purple nutsedge. Purple nutsedge and false-green kyllinga were more sensitive than yellow nutsedge to sulfosulfuron, while evaluated species responded similarly to trifloxysulfuron. Soil-only and soil + foliage-applications provided the highest level of growth suppression, indicating herbicide-soil contact is required for optimum sedge control with evaluated herbicides.