Annual Bluegrass Control During Hybrid Bluegrass Establishment from Sprigs

Hybrid bluegrass (Poa arachnifera Torr. x P. pratensis L.) establishment may be compromised by the emergence of annual bluegrass (P. annua L.) in the fall. The objective of this research was to evaluate the efficacy of herbicides for annual bluegrass control during the establishment of ‘DALBG 1201’ hybrid bluegrass from sprigs. Herbicides were applied at two timings: 5 d after planting (DAP) or 3 wk after planting (WAP). Hybrid bluegrass cover was rated four times between 9 and 33 WAP. The first and second visual ratings of annual bluegrass cover were made between 16 and 18 and 30 to 33 WAP, respectively. At 26 WAP, hybrid bluegrass cover was approximately two-fold in plots treated with mesotrione, oxadiazon, or topramezone compared with the nontreated. Primisulfuron applied singly or sequentially at 0.04 kg ha⁻¹ controlled annual bluegrass ³88% but reduced hybrid bluegrass cover >30% relative to the nontreated. Ethofumesate applied at 0.84 kg ha⁻¹ at 3 WAP controlled annual bluegrass 74%. Oxadiazon at 1.12 or 2.24 kg ha⁻¹ applied 5 DAP controlled annual bluegrass 67 to 75% at 30 WAP without reducing hybrid bluegrass cover. All other treatments provided poor (<70%) control of annual bluegrass. Overall, hybrid bluegrass was tolerant to ethofumesate, oxadiazon, mesotrione, and topramezone at rates evaluated during establishment from sprigs. Programs that included ethofumesate at 0.84 kg a.i. ha⁻¹ or oxadiazon at 1.12 or 2.24 kg ha⁻¹ provided best annual bluegrass control and improved hybrid bluegrass cover from the nontreated.