Bispyribac-sodium selectively controls annual bluegrass in cool-season turf but efficacy may be influenced by management practices, such as plant growth regulator use. Experiments were conducted in New Jersey to investigate efficacy and absorption of bispyribac-sodium applied with trinexapac-ethyl for annual bluegrass control and turfgrass tolerance. In laboratory experiments with annual bluegrass, creeping bentgrass, and perennial ryegrass, tank-mixing trinexapac-ethyl with ¹⁴C-bispyribac-sodium increased presumed foliar absorption of ¹⁴C-bispyribac-sodium compared with nontrinexapac-ethyl treated; absorption increased with trinexapac-ethyl rate. Differences in ¹⁴C-bispyribac-sodium absorption were not detected among emulsifiable concentration, microencapsulated concentration, and wettable powder trinexapac-ethyl formulations. In field experiments, sequential bispyribac-sodium applications controlled annual bluegrass 93%, but trinexapac-ethyl did not affect efficacy. Tank-mixing all trinexapac-ethyl formulations with bispyribac-sodium provided similar annual bluegrass control and creeping bentgrass quality compared with bispyribac-sodium alone. Applications of bispyribac-sodium reduced dollar spot cover in both years, whereas trinexapac-ethyl reduced dollar spot cover only in 2005.

Nomenclature: Bispyribac-sodium; annual bluegrass, Poa annua L.; creeping bentgrass, Agrostis stolonifera L., ‘L-93’, ‘G-2; perennial ryegrass, Lolium perenne L., ‘Applaud’.