Seashore Paspalum and Bermudagrass Response to Spray Applications of Postemergence Herbicides

Abstract

<jats:p>The use of nonpotable water for irrigation on various sport venues has led to an increased use of seashore paspalum (<jats:italic>Paspalum vaginatum</jats:italic>) turf in Hawaii. An ongoing challenge many seashore paspalum turf managers struggle with is bermudagrass (<jats:italic>Cynodon dactylon</jats:italic>) infestations. Herbicide efficacy studies were conducted at the Hoakalei Country Club [‘SeaDwarf’ seashore paspalum (fairway cut)] and the Magoon Research Station [‘SeaStar’ seashore paspalum (grown in container)] on the island of Oahu in Hawaii. Spray applications of the herbicides mesotrione, topramezone, metribuzin, and ethofumesate were evaluated alone and in tank mixtures for bermudagrass suppression and seashore paspalum injury. At the Hoakalei Country Club, maximum bermudagrass injury with minimal seashore paspalum discoloration was obtained with tank mixes of mesotrione (0.06 lb/acre) + metribuzin (0.19 lb/acre) + ethofumesate (1.00 lb/acre) and topramezone (0.02 lb/acre) + metribuzin (0.19 lb/acre) + ethofumesate (1.00 lb/acre). Unacceptable seashore paspalum turf injury was obtained in all treatments that did not include metribuzin. At the Magoon Research Station, maximum selective bermudagrass suppression was achieved with tank mixes of topramezone (0.01 lb/acre) + ethofumesate (1.00 lb/acre) and topramezone (0.01 lb/acre) + metribuzin (0.09 lb/acre) + ethofumesate (1.00 lb/acre). The addition of metribuzin and/or ethofumesate to the tank mix safened (reduced turf discoloration) seashore paspalum to topramezone or mesotrione foliar bleaching. Tank mixes of mesotrione, topramezone, metribuzin, and ethofumesate have the potential for bermudagrass suppression and control of other grassy weeds in seashore paspalum turf.</jats:p>

Differences in selectivity between bermudagrass and goosegrass (Eleusine indica) to low-rate topramezone and metribuzin combinations

“…Investigation of topramezone at these rates on bermudagrass safety or D. ischaemum control have not been previously reported. Topramezone applied at 5 to 20 times higher rates than the current study and mixed with metribuzin injured bermudagrass greater than 50%, but the bermudagrass recovered to an acceptable injury level (≤30%) after 7 d in Hawaii (Lindsey et al 2019(Lindsey et al , 2020. Only one study has evaluated mesotrione in combination with metribuzin at rates similar to those in the current study.…”

“…Currently, there are three papers that have been published evaluating topramezone plus metribuzin in turfgrass. Two evaluated the use of topramezone with or without metribuzin for common bermudagrass suppression and E. indica control in seashore paspalum (Paspalum vaginatum Sw.) (Lindsey et al 2019(Lindsey et al , 2020. Topramezone at 10 g ha −1 plus metribuzin at 100 g ha −1 was observed to control E. indica 90% to 100% (Lindsey et al 2020).…”

“…Even at these lower topramezone rates, bermudagrass is still subject to severe phytotoxicity in the form of foliar bleaching that can persist for multiple weeks (Brewer et al 2016;Cox et al 2017;Elmore et al 2011b). This injury tends to last longer in the transition zone than areas further south due to the shorter growing season and lower accumulation of heat units (Cox et al 2017;Breeden et al 2017;Kerr et al 2019b;Lindsey et al 2019;Stanford et al 2005). Topramezone would be a more viable E. indica control option for turfgrass managers in the transition zone if programs could be developed to reduce foliar bleaching and injury duration to bermudagrass while also maintaining E. indica control efficacy.…”

Tropical Signalgrass Control in Seashore Paspalum

“…Several of these herbicides are rated for broadleaf weeds; however, this study reinforces the difficulty of selecting and using herbicides that will not injure seashore paspalum above threshold (<30%). In 2019, Lindsey conducted a study to evaluate POST herbicide options for bermudagrass encroachment into seashore paspalum [7]. Plots were rated as % green color, 0 being completely brown or white, and 100 being maximum attainable green color.…”

“…Plots were rated as % green color, 0 being completely brown or white, and 100 being maximum attainable green color. In one trial, topramezone individually applied to 'SeaDwarf ' seashore paspalum at 0.02 lb ai/acre (0.022 kg ai/ha) had the worst injury on seashore paspalum with ~23 percent green color at 14 DAIT; however was recovered to ~94 percent green color by 22 DAIT; however, when replicated in containers, bermudagrass recovered to 97% at 21 DAIT following an initial rating of ~20% at 7 DAIT [7]. This study is further proof of the scarceness of pesticides labelled for seashore paspalum that can control warmseason grassy weeds.…”