Using ethephon for seedhead suppression of ‘KSUZ 0802’ (Innovation) zoysiagrass

‘KSUZ 0802’ zoysiagrass (Innovation zoysiagrass, Zoysia matrella × Z. japonica) is a new cultivar that provides a high-quality playing surface on golf course fairways and tees. However, seedheads produced in late spring disrupt the playing surface. The plant growth regulator (PGR) ethephon has produced variable results in prior studies in suppressing zoysiagrass seedheads, and information for KSUZ 0802 is lacking. A two-year field experiment was conducted from 2019–2021 in Manhattan, KS, to assess the performance of ethephon (Proxy) on seedhead suppression of KSUZ 0802 zoysiagrass. Treatments included ethephon applied in a single application at 5 fl. oz. 1000 ft⁻² on multiple dates between August and November. Seedhead suppression was determined by counting seedheads in late spring. Ethephon applied in September provided >60% seedhead suppression; however, when applied during other months, variations were large between the two study years. Applying ethephon when accumulated cooling degree days (68°F base) were <37 resulted in >70% seedhead suppression, except for application on September 25, 2019. Late August ethephon applications, despite achieving good seedhead suppression (ranging from 54 to 80%), caused transient yet commercially unacceptable injury to KSUZ 0802 in both years. Application timing affected turf quality in late spring as KSUZ 0802 with fewer seedheads had better quality post-mowing, but no effect on spring greenup was observed. Ethephon can be an effective PGR for seedhead suppression in KSUZ 0802 zoysiagrass. However, careful consideration of application timing is essential as applying ethephon in late summer or late autumn can produce undesirable results.