Weed Control Strategies for Improved Establishment of Seeded ‘Zenith' Zoysiagrass.

Controlling weed competition during seeded zoysiagrass (Zoysia spp.) establishment is necessary to expedite turf development. Crabgrass (Digitaria spp.), goosegrass (Eleusine indica (L) Gaertn.), and other grassy and broadleaf weeds suppress zoysiagrass seedlings through direct competition.  Previous research demonstrates fluazifop and fenoxaprop controls various grass weed species, but injures emerging zoysiagrass.  It has also been reported that siduron is safe to apply at zoysiagrass seeding for weed control.  Further research demonstrated safening of fluazifop and fenoxaprop to zoysiagrass when tank-mixed with triclopyr.  Research was conducted to evaluate the use of fluazifop (0.11 kg ai/ha), fenoxaprop (0.14 kg ai/ha), triclopyr (1.12 kg ai/ha), fluazifop plus triclopyr (0.11 kg ai/ha + 1.12 kg ai/ha), fenoxaprop plus triclopyr (0.14 kg ai/ha + 1.12 kg ai/ha), and siduron (6.7 kg ai/ha) for weed control during seeded ‘Zenith’ zoysiagrass (Zoysia japonica Steud.) establishment.  A randomized complete block design with a strip-plot arrangement of treatments was selected, and plots were stripped with and without siduron applied at seeding.  Other herbicides were applied as a single application 2 weeks after emergence (WAE) or sequential applications 2 and 6 WAE.  Siduron applied at seeding led to improved zoysiagrass cover (61%) compared to the non-treated (10%) and reduced Digitaria cover (≤4%) compared to the non-treated (82%).  However, siduron alone was not effective in controlling Eleusine (39% cover).  Single and sequential treatments of fluazifop and fluazifop plus triclopyr effectively controlled Eleusine (≤4% cover) but were ineffective in Digitaria control (≥35% cover).  Fenoxaprop and fenoxaprop plus triclopyr exhibited less control of Eleusine (≥12% cover) but sequential applications controlled both Eleusine (0%) and Digitaria (≤6%) cover.  Herbicide treatments that minimized weed pressure led to more zoysiagrass cover.  Results indicate that siduron treatments at seeding provided effective Digitaria control.  If siduron treatments are not an option, sequential applications of fenoxaprop plus triclopyr at 2 and 6 WAE will provide efficient weed control during seeded ‘Zenith’ zoysiagrass establishment.