Evaluation of florpyrauxifen-benzyl for control of Old World climbing fern

Abstract

Old World climbing fern [Lygodium microphyllum (Cav.) R. Br.; OWCF] is an invasive vine in many Florida wetlands. Management involves poodle cutting the climbing rachis at approximately 120 cm, with a subsequent foliar application of glyphosate to the remaining rooted vines. Recently, there has been increasing interest in synthetic auxin herbicides for OWCF control. Florpyrauxifen-benzyl is a new auxin mimic that was developed for weed control in aquatics and is selective at low use rates. There is limited information regarding its activity on OWCF. We conducted field studies at four wetland sites in south Florida from 2017 to 2020 to evaluate the effectiveness of florpyrauxifen-benzyl for OWCF control. In small-plot studies at two locations, florpyrauxifen-benzyl applied at 0.08 and 0.16 g L 1 reduced OWCFcover to 4%at 3 moafter treatment (MAT) and 21% at 6 MAT.However, florpyrauxifen-benzyl at these concentrations did not consistently control OWCF at 12 MAT. An additional study evaluated banded applications of florpyrauxifen-benzyl or glyphosate compared to poodle cutting for control of the climbing rachis. For both herbicides, banded applications did not control the climbing rachis, whereas poodle cutting provided complete control of all climbing rachis. Finally, an operational field study demonstrated florpyrauxifen-benzyl applied by professional applicators at 0.16 g L 1 reduced OWCF cover to 9% at 17 MAT and was not different from glyphosate applied at 14.4 g L 1. These studies indicate florpyrauxifen-benzyl is active on OWCF and future research should evaluate the effectiveness of repeat applications for longer-term control.