Evaluation of EPTC as a Preplant Soil Treatment in Warm-Season Sod Production

Abstract

Field research was conducted at Auburn University Turfgrass Research Unit (AUTRU) Auburn AL, during 2008 to 2010 and Gulf Coast Research and Extension Center (GCREC) Fairhope AL in 2009, to evaluate EPTC as a preplant soil treatment in warm-season sod production and to determine if 2,4-D could be used as a potential safener for EPTC on three warm-season turfgrasses. For all three plant-back intervals, Palmetto St. Augustinegrass planted 1 week after treatment (1 WAT) at AUTRU showed significant dry weight differences among chemical treatments in both 2008 and 2009; similar treatment differences were not seen in the GCREC study. St. Augustinegrass planted 1 WAT produced similar or significantly higher dry weight, average stolon length or percent ground coverage than those planted back 2 WAT or 3 WAT at both locations. BK-7 zoysiagrass was less sensitive to EPTC applied alone or with dazomet. Plant-back interval comparisons suggested zoysiagrass could be planted back 1 week after EPTC or EPTC + dazomet treatment without receiving significant injury. Tifway bermudagrass planted at GCREC showed great sensitivity to EPTC. Previously described 2,4-D safening on corn and soybean against EPTC injury was not seen on bermudagrass or any of the turfgrass used at GCREC. Addition of the fumigant dazomet with EPTC did not adversely affected bermudagrass growth more than EPTC applied alone and this was also confirmed by the AUTRU cucumber bioassay, in which no significant dry weight differences could be found within EPTC and EPTC plus various rates of dazomet. GC-MS analysis of EPTC retention under field conditions indicated that EPTC applied at 7.84 kg ai/ha rate in July would be degraded to very low concentration (around 0.01 ppm) in the top 7.5 cm soil within 7 days. GC-MS analysis also proved that a high rate of dazomet usage in previous years would increase enhanced biological degradation of EPTC the following year due to structural similarity.