Characterization of rice cultivar response to florpyrauxifen-benzyl

Abstract

Many factors such as environment, herbicide rate, growth stage at application and days between sequential applications can influence response of a crop to herbicides. Florpyrauxifen-benzyl is a new broad-spectrum, POST herbicide commercialized in U.S. rice in 2018. Field experiments were conducted in 2018 at the Pine Tree Research Station (PTRS) near Colt, AR, and the Rice Research and Extension Center (RREC), near Stuttgart, AR, evaluating crop injury and yield response of three rice cultivars to sequential applications of florpyrauxifen-benzyl. Greenhouse and growth chamber experiments were conducted at the Altheimer Laboratory in Fayetteville, AR, evaluating cultivar responses when florpyrauxifen-benzyl was applied at 30 or 60 g ae ha -1 to rice exposed to different temperature regimes or at various growth stages. Three rice cultivars were used in all experiments: long-grain variety ‘CL111’, medium-grain variety ‘CL272’, and long-grain hybrid cultivar ‘CLXL745’. CL111 exhibited sufficient tolerance to florpyrauxifen-benzyl with only 10% visible injury and no effect on yield. CL272 showed 15% injury 3 wks after the second application in the field experiment when applications were made 14 d apart. Additionally, 12% injury was observed in the greenhouse when florpyrauxifen-benzyl was applied at 30 g ae ha -1, averaged over growth stages at application. Florpyrauxifen-benzyl did not reduce the yield of CL272 in the field, indicating CL272 can recover from florpyrauxifen-benzyl injury. As much as 64% injury was observed for CLXL745 at 3 weeks after application (WAA) when sequential herbicide applications were made 4 d apart. High levels of injury occurred in the growth chamber and greenhouse studies for this cultivar as well. Sequential applications of florpyrauxifen-benzyl reduced yields of CLXL745 in nearly all treatments. Data from these experiments suggest CL272 and CLXL745 are sensitive to sequential applications of florpyrauxifen-benzyl. Growers must follow the prescribed guidelines for using florpyrauxifen-benzyl in these cultivars and others like it.

Rice Cultivar Response to Florpyrauxifen-Benzyl When Applied with Imazethapyr and a Cytochrome P450 Inhibitor

“…Generally, applications made at the 5-leaf growth stage exhibited higher levels of injury 2 WAA and could be due to proximity to flooding and anaerobic environment; however, by 4 WAA most of this injury was nonexistent. ese results appear to be contradictory to the results from experiments conducted by Wright et al [23], where 1-leaf rice was more injured than 5-leaf rice. However, that experiment was conducted in a controlled environment, whereas the injury observed in this experiment was the result of a field experiment conducted in an uncontrolled environment.…”

“…However, that experiment was conducted in a controlled environment, whereas the injury observed in this experiment was the result of a field experiment conducted in an uncontrolled environment. Additionally, results from Wright et al [23] indicate warmer temperatures can increase visual injury. In this experiment, daily high temperatures at the time of and following the 5leaf application were above or near 30°C, which could explain the injury observed.…”

Florpyrauxifen-Benzyl Selectivity to Rice

“…Our results were similar to others experiments carried out in greenhouse conditions in Arkansas, where the rice injury caused by FPB (30 g ai ha −1 ) was higher at 1-leaf (15%) than at 5-leaf rice (4%) [35]. Raising the rate of FPB and the growth stage of spraying was similar to the results observed for triclopyr (another auxin herbicide).…”

“…Previous rice crop observations have described leaf malformations, stem curling, chlorosis, height, tiller number reduction, and shoot dry weight reduction as common symptomology of FPB in rice [35]. Recent research has investigated rice cultivar's response to FPB regarding the temperature surrounding spraying time, growth stage application, and tank-mix with imazethapyr and malathion [35,36]. However, the effect of planting time, growth, and quantifying the effect of inhibitors on the dose of FPB or genes expression related to metabolism or bio-activation have not been fully described.…”

“…Previous rice crop observations have described leaf malformations, stem curling, chlorosis, height, tiller number reduction, and shoot dry weight reduction as common symptomology of FPB in rice [35]. Recent research has investigated rice cultivar's response to FPB regarding the temperature surrounding spraying time, growth stage application, and tank-mix with imazethapyr and malathion [35,36].…”