Application Timing Affects Tolerance of Zoysiagrass to Fluazifop‐P‐butyl and Safening Effect of Triclopyr

Abstract

ABSTRACTAryloxyphenoxypropionate (AOPP) herbicides, such as fluazifop‐P‐butyl, can be used for postemergence control of grassy weeds in zoysiagrass (Zoysia spp.), although the turf might suffer transient injury. This injury can be reduced by tank mixing fluazifop‐P‐butyl with triclopyr, an herbicide that behaves as a safener for AOPP herbicides. To characterize seasonal variation in zoysiagrass injury caused by fluazifop‐P‐butyl and triclopyr applications, we conducted a 2‐yr study on three Zoysia spp. cultivars (‘Empire’, ‘Geo’, and ‘Zeon’) at Jay, FL, from August 2015 to April 2017, evaluating how injury and turf quality were affected after spring, summer, and fall applications. The level of injury and changes in turf quality were influenced by fluazifop‐P‐butyl application timing, but the most sensitive season varied with the cultivar. The seasons with the greatest injury were also the ones in which the safening activity of triclopyr was most effective. In addition, when triclopyr was applied with fluazifop‐P‐butyl, the quality of all evaluated cultivars recovered to the level of nontreated controls by 2 wk after treatment. Nonstructural carbohydrate content was not affected by herbicide applications, but there were major differences in glucose and starch content between above‐ and belowground tissue depending on cultivar and season. Overall, our study confirmed that tank mixing triclopyr can reduce fluazifop‐P‐butyl phytotoxicity in zoysiagrass, and in the case of relatively tolerant cultivars, it might allow the use of rates higher than the current labeled rate with little negative impact on turf quality while providing better control of both broadleaf and grassy weeds.