Golfdom, December 2016

Super Science FIGURE 3 Diamond zoysiagrass seedhead emergence in spring Continued from page 35 paspalum seedheads declined in September from peak levels consistent with trends in turf quality DIAMOND ZOYSIAGRASS Seedhead emergence Zoysiagrass had two flushes of seedhead emergence in spring and fall while turf quality increased from spring to summer and declined in fall Figure 3 Peak emergence was noted in May and October for the spring and fall seedhead flushes respectively and declined from May to August and October to December respectively Diamond zoysiagrass generally did not go completely dormant in the winter at any mowing height The initial seedhead emergence was consistent over years from calendar dates growing degree day and photoperiod across all mowing regimens The initial seedhead emergence occurred within approximately eight calendar days for the spring and fall timings over years These dates had photoperiods ranging from 127 to 129 hour in both fall and spring The growing degree day on dates of initial seedhead emergence in spring and fall ranged 167 to 196 and 1949 to 2230 respectively in all years across mowing regimens Seedhead production Seedhead cover from January to peak emergence in spring had a stronger association with temperature compared with photoperiod Reduction in photoperiod from July to October had a greater influence than calendar date and temperature growing degree day for zoysiagrass seedhead cover during this period PGR APPLICATION TIMING Research was conducted over three years to evaluate the efficacy of PGRs applied at various timings based on cumulative temperature measurements growing degree days Two PGR treatments including ethephon trinexapac ethyl TE or mefluidide were applied at five growing degree day timings 139 278 556 833 or 1111 C 250 500 1000 1500 2000 F with a base temperature of 10 FIGURE 4 Seashore paspalum plots used for PGR application timing research for seedhead control in 2014 FIGURE 5 Seashore paspalum injury from ethephon plus trinexapac ethyl treatments degrees C 50 F beginning Jan 1 The application rates and products used for treatments included ethephon Proxy 2L Bayer Environmental Science plus trinexapac ethyl Primo Maxx 1ME Syngenta Crop Protection at 5 oz 1000 sq ft 55 oz acre respectively or mefluidide Embark 2S PBI Gordon at 05 lb a i acre Seedhead cover was rated weekly for four weeks after treatments on a percent scale Turfgrass injury was visually rated weekly on a percent scale Figure 4 The ethephon trinexapac ethyl TE treatment provided approximately three times greater seedhead control of bermudagrass than mefluidide at all application timings However seedhead control never exceeded 69 percent on bermudagrass from one to four weeks after treatment The ethephon TE treatments also were more effective than mefluidide for controlling seashore paspalum seedheads on every date Control ranged from 75 percent to 82 percent from two to four weeks after treatment with ethephon TE However this treatment caused excessive injury 30 percent on several dates and is not recommended for superintendents Figure 5 36 Golfdom December 2016 Golfdom com