Response of St. Augustinegrass cultivars to pinoxaden alone and in combination with select fungicides

Abstract

Pinoxaden is a herbicide inhibiting acetyl coenzyme A carboxylase recently introduced for use in turfgrass. Currently, pinoxaden is labeled for use in all bermudagrass [Cynodon dactylon (L.) Pers.] and zoysiagrass (Zoysia spp.) turfgrass areas except putting greens. However, pinoxaden is only labeled for use in St. Augustinegrass [Stenotaphrum secundatum (Walter) Kuntze] sod production because of injury concerns. Tank mixtures of two or more herbicides can reduce injury to turfgrass species. Injury reduction can also occur when fungicides are tank‐mixed with herbicides. Research was conducted between 2018 and 2019 to determine the effect that pinoxaden alone and tank mixtures of pinoxaden with one of two common fungicides, chlorothalonil and propiconazole, would have on four different cultivars of St. Augustinegrass: ‘Classic’, ‘Floratam’, ‘Palmetto’, and ‘Raleigh’. At the conclusion of the study, we determined that there is differential susceptibility to pinoxaden between cultivars of St. Augustinegrass and that both chlorothalonil and propiconazole have a safening effect on pinoxaden applications to St Augustinegrass, regardless of cultivar. The cultivars Classic and Raleigh were more susceptible to pinoxaden than Floratam and Palmetto. All four cultivars were less susceptible to pinoxaden when chlorothalonil and propiconazole were applied in combination with pinoxaden. These results suggest that pinoxaden can be applied in a tank mixture with either chlorothalonil or propiconazole to reduce pinoxaden injury to St. Augustinegrass. However, the effect that these tank mixtures may have on weed control is currently unknown.

Evaluation of goosegrass response to combinations of topramezone and chlorothalonil

“…Robinson et al (2013) observed transient injury in wheat ( Triticum aestivum L.) when tebuconazole was applied with herbicides such as 2,4-D and bromoxynil. Transient injury was observed when chlorothalonil was applied with pinoxaden and MSO to St. Augustinegrass (Peppers et al 2020). The description of this transient injury in both wheat and St. Augustinegrass is consistent with that caused by surfactants; however, data that would support this claim was not collected in either study.…”

“…Previous research suggest that fungicides could alter herbicidal performance in turfgrass systems, such as occurs with pinoxaden in St. Augustinegrass [ Stenotaphrum secundatum (Walter) Kuntze] (Peppers et al 2020). We hypothesize that the same could be true when mixtures of topramezone and chlorothalonil are applied for goosegrass and disease control.…”

Growth Stage of Alopecurus myosuroides Huds. Determines the Efficacy of Pinoxaden

“…ha −1 controlled A. myosuroides slightly weaker compared to A. spica-venti [ 36 ]. Differences in susceptibility to pinoxaden among other grass weed species was reported in a greenhouse study [ 39 ]. Our findings showed that the ability of pinoxaden to control A. myosuroides was strongly dependent on whether or not the A. myosuroides stem was elongating at the time of application, and consequently, the importance of adjusting the application time based on the growth stage of the weed is highlighted.…”