Evaluation of WideStrike Cotton Response to Repeated Applications of Glufosinate at Various Application Timings

Abstract

Glyphosate-resistant (GR) weeds are most challenging for growers to control in cotton in the midsouth region of the United States. As a result, growers in these states are transitioning from a glyphosate-based system to a glufosinate-based system. A field study was conducted in 2010 and 2011 in Georgia, North Carolina, and Tennessee to determine the effect of repeated glufosinate applications to WideStrike cotton applied at various application timings. One to three glufosinate applications at 594 g ai ha−1were applied to cotton at the two-leaf, seven-leaf, bloom, or 2 wk after bloom stages. Visual estimates of crop injury were evaluated after each application, in addition to crop height, development, and yield. Crop injury after each glufosinate application typically ranged from 3 to 11%, with higher injury observed where multiple glufosinate applications were made. Crop height differences were noted after the bloom and 2 wk after bloom applications. Treatments that had one, two, or three glufosinate applications had reduced crop height when compared with the weed-free control. Node above cracked boll ratings also indicated that glufosinate treatments may have stressed the cotton. Ultimately, yield was reduced where three glufosinate treatments were applied to WideStrike cotton. In addition, one glufosinate application at the bloom stage or two glufosinate applications at the bloom and 2 wk after bloom stages reduced yield when compared with the weed-free control. Although it is a legal application, growers should use caution when applying glufosinate to WideStrike cotton because the manufacturer of glufosinate and the manufacturer of WideStrike cotton do not recommend this application. However, where GR Palmer amaranth is present, these applications may be necessary.

LibertyLink®, WideStrike® and XtendFlex® Tolerance to Late Postemergence Applications of Glufosinate and S-Metolachlor

“…Visual Injury Ratings. Visual injury ratings captured from the WideStrike (PHY 333 WRF) treatments are consistent with injury reported by Steckel et al (2012) and Culpepper et al (2009), slightly higher than those observed by Barnett et al (2015), and lower than those observed by Stewart et al (2013). Steckel et al (2012) reported 18 and 23% average injury from glufosinate and glufosinate plus S-metolachlor, respectively.…”

“…reported 14% and 20% injury from a single application of glufosinate and an application of glufosinate plus S-metolachlor, respectively, but application rates of glufosinate in their studies were lower (430 g ai ha -1 instead of 594 g ai ha -1 ). Barnett et al (2015) applied glufosinate at similar application rates but noted less injury (11% max at 5 DAA). Differences in injury could be due to differences in tested cultivars and environmental conditions surrounding the application timing or the growth stage; in this study, sequential applications were stacked at the end of the application window.…”

Injury potential of herbicide combinations on XtendFlex® cotton

“…These authors also reported cotton yield reduction for glufosinate þ glyphosate (1,200 kg ha -1 ), glufosinate þ S-metolachlor (1,250 kg ha -1 ), and glufosinate þ glyphosate þ S-metolachlor (1,170 kg ha -1 ) tank mixtures when compared to the control (1,470 kg ha -1 ). Barnett et al (2015) reported 3% to 11% injury to WideStrike® cotton following POST applications of glufosinate, where higher injuries were observed with multiple glufosinate applications. These authors also observed that one, two, and three POST glufosinate applications negatively influenced cotton height and NACB, whereas three glufosinate applications reduced cotton yield (Barnett et al 2015).…”

“…Barnett et al (2015) reported 3% to 11% injury to WideStrike® cotton following POST applications of glufosinate, where higher injuries were observed with multiple glufosinate applications. These authors also observed that one, two, and three POST glufosinate applications negatively influenced cotton height and NACB, whereas three glufosinate applications reduced cotton yield (Barnett et al 2015). Applications of glufosinate þ glyphosate increased crop injury observed herein at 3 (27%) and 7 DAA (16%) when compared to applications of the two respective herbicides alone (18% and 11% for glufosinate; and 13% and 8% for glyphosate) (Table 3).…”

Cotton cultivar response to glufosinate plus S-metolachlor applied postemergence using two nozzle types

“…One to two postemergence applications of glufosinate to WideStrike cotton have been documented to cause visible plant injury ranging from 5% to 25% without having a negative effect on yield (Culpepper et al 2009;Dodds et al 2015;Whitaker et al 2011a). Three applications of glufosinate to WideStrike cotton, however, have been shown to reduce yield up to 7% (Barnett et al 2015). Glufosinate applications in combination with other herbicides have also been shown to delay cotton maturity and reduce yield (Steckel et al 2012).…”