F9001 FOR PREEMERGENCE YELLOW NUTSEDGE CONTROL. G.K. Breeden*, J. Brosnan, M. Elmore, and B. Walls, University of Tennessee, Knoxville, TN (14)

ABSTRACT

   Yellow nutsedge (Cyperus esculentus) is a problematic weed in both warm- and cool-season turf. F9001 is a new preemergence herbicide mixture of sulfentrazone (206.3 g ai/L) + dithiopyr (273.5 g ai/L). Two research trials were conducted in 2010 evaluating the efficacy of soluble concentrate (SC) and granular (G) formulations of F9001 for preemergence control of yellow nutsedge. 
   Both trials were conducted on a mature stand of bermudagrass (Cynodon dactylon) maintained as a golf course rough at the Plant Science Unit of the East Tennessee Research and Education Center in Knoxville, TN.  Plots (1.5 by 3 m) were arranged in a randomized complete block design with three replications.  Three rates of F9001 SC (493 g ai/ha, 706 g ai/ha and 908 g ai/ha), dithiopyr (426 g ai/ha), and sulfentrazone (281 g ai/ha) + prodiamine (562 g ai/ha) were applied at early (EPRE) and late preemergence (LPRE) timings on 31 March and 14 April, respectively.  On each date treatments were applied with a CO2 powered boom sprayer calibrated to deliver 280.5 L/ha utilizing four, flat-fan, 8002 nozzles at 124 kPa, configured to provide a 1.5-m spray swath. In a separate study, three rates of F9001 G (493 g ai/ha, 706 g ai/ha and 908 g ai/ha), dithiopyr (426 g ai/ha), and sulfentrazone (281 g ai/ha) + prodiamine (562 g ai/ha) were applied by hand on the same dates. All F9001 G treatments were impregnated on a fertilizer carrier. Weed control and turf injury were evaluated visually utilizing a 0 (no weed control or turf injury) to 100 (complete weed control or turf injury) % scale. Data were collected at 21, 29 42, 75, 105, and 134 days after initial treatment (DAIT).

At no time during this study was bermudagrass injury observed. Applied EPRE, F9001 SC at ≥706 g ai/ha controlled yellow nutsedge ≥ 88% at 105 DAIT through the end of the study. F9001 SC at 493 g ai/ha applied EPRE controlled yellow nutsedge 83% at 105 and 134 DAIT. All rates of F9001 SC applied LPRE controlled yellow nutsedge ≥87% on all rating dates.  F9001 G applied EPRE and LPRE at 908 g ai/ha controlled yellow nutsedge ≥ 87% at all rating dates. EPRE applications of F9001 G at ≤ 706 g ai/ha controlled yellow nutsedge ≤ 85% at 105 DAIT through the end of the study. LPRE applications of F9001 G at rates ≤ 706 g ai/ha controlled yellow nutsedge ≤ 90% at 105 DAIT through the end of the study. Applied EPRE and LPRE, sulfentrazone + prodiamine controlled yellow nutsedge ≥87% at 105 DAIT. Sulfentrazone + prodiamine control of yellow nutsedge reduced to ≤83% at 134 DAIT for both timings. Both formulations of dithiopyr controlled yellow nutsedge 0% at all rating dates. These data suggest that F9001 can be used to provide preeemergence control of yellow nutsedge.