Abstract
Understanding cultivar responses to a new herbicide is crucial to determining appropriate herbicide use and management practices. Florpyrauxifen-benzyl is a new rice herbicide developed to control troublesome weeds in rice production. Little research has been conducted to characterize rice cultivar responses to florpyrauxifen-benzyl, and thus, a field experiment was conducted at the Pine Tree Research Station (PTRS) in 2017 and 2018 and at the Rice Research and Extension Center (RREC) in 2018 to determine rice cultivar tolerance to florpyrauxifen-benzyl as influenced by herbicide rate, the addition of imazethapyr, and rice growth stage. Another experiment was conducted in 2018 at PTRS and RREC to assess crop response when florpyrauxifen-benzyl at different rates is applied with and without malathion, a known cytochrome P450 inhibitor. Three cultivars were evaluated in both experiments: a long-grain variety “CL111,” a medium-grain variety “CL272,” and a long-grain hybrid “CLXL745.” Injury in the first experiment was higher when florpyrauxifen-benzyl was applied at 60 g ae ha−1 than at the labeled rate of 30 g ha−1, with the most injury being 10% when averaged over growth stage at the time of application. Generally, applications made at the 3-leaf growth stage resulted in the most injury; however, this injury was at most 14%. Additionally, there was no reduction in grain yield for any cultivar, indicating florpyrauxifen-benzyl can be used safely in conjunction with imazethapyr in imidazolinone-resistant rice. In the second experiment, there was no more than 10% injury and no reduction in grain yield, with the addition of malathion not causing an increase in rice injury. Results from these experiments indicate florpyrauxifen-benzyl can be mixed with imazethapyr and the addition of malathion will not lead to increased risk for injury to rice.
Highlights
Crop tolerance to a herbicide, in most instances, is due to the ability of the plant to metabolize and detoxify the toxin to a nonphytotoxic compound, with the most common detoxifying pathways being P450 monooxygenase and glutathione S-transferase (GST) enzymes [1]
E experiment was conducted with a randomized complete block, two-factor factorial design with four replications. e first factor was the rate of florpyrauxifenbenzyl, and the second factor was the crop stage. ree rice cultivars were planted in separate trials on May 17, 2017, at Pine Tree Research Station (PTRS) and April 19, 2018, at both locations using a 10-row drill with 18 cm row spacing
Nonionic surfactant was added to imazethapyr-only treatment at 0.25% v/v. e 1-leaf applications were made on May 11 and 14, 3-leaf applications were made on May 16 and 17, and 5-leaf applications were made on May 28 and 30 at Research and Extension Center (RREC) and PTRS in 2018, respectively
Summary
Crop tolerance to a herbicide, in most instances, is due to the ability of the plant to metabolize and detoxify the toxin to a nonphytotoxic compound, with the most common detoxifying pathways being P450 monooxygenase and glutathione S-transferase (GST) enzymes [1]. Bond et al [8] found that a 12.5% drift rate of acetolactate synthase (ALS)-inhibiting herbicides on non-imidazolinone-resistant rice resulted in as much as 35% injury 7 days after application when applied early postemergence (EPOST) on 2- to 3-leaf rice compared to 0% when application was made at panicle differentiation as a late-postemergence (LPOST) application. Of these, red rice and barnyardgrass are the most difficult to control and, when not controlled can cause as much as 82% and 65% yield loss at 40 and 50 plants m−2, respectively [12] Further complicating this issue, 45% of Arkansas rice is planted to an imidazolinone-resistant cultivar and will receive an application of an imidazolinone herbicide at least once during the growing season [13]. E objectives of these experiments were to further quantify cultivar tolerance to florpyrauxifen-benzyl when applied with a cytochrome P450-inhibiting insecticide and when mixed with imazethapyr
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