Annual Bluegrass (Poa annua) Control with Fall Applications of Trifloxysulfuron-Sodium and Foramsulfuron.

Field research was initiated in Ft. Worth, Wharton, and San Antonio, TX in 2014 to evaluate single October or November applications of trifloxysulfuron-sodium for annual bluegrass control. Trifloxysulfuron-sodium (28 g ha^-1) applied in November 2014 provided >97% annual bluegrass in spring 2015. Control from trifloxysulfuron-sodium applied in November was greater than or equal to that provided by indaziflam (33 g ha^-1) in October. Trifloxysulfuron-sodium applied in November provided greater control than October applications in Wharton, but timing did not affect control in Ft. Worth and San Antonio.

In 2015, two separate experiments in Dallas, TX evaluated trifloxysulfuron-sodium (28 and 19 g ha^-1) and foramsulfuron (29 g ha^-1) applied singly in early or late November. Indaziflam (33 g ha^-1), prodiamine (1120 g ha^-1), and prodiamine + trifloxysulfuron-sodium (1120 + 19 g ha^-1) were included for comparison. Treatments were evaluated in April 2016. Grid counts determined that trifloxysulfuron-sodium provided greater annual bluegrass control than foramsulfuron at both rates and timings. Late November applications of trifloxysulfuron-sodium at 28 g ha^-1 provided ≥97% annual bluegrass control. All treatments containing trifloxysulfuron-sodium provided similar (≥90%) annual bluegrass control. Trifloxysulfuron-sodium application timing and rate did not affect annual bluegrass control in 2015 experiments.