Pre- and Postemergence Annual Bluegrass Control with Indaziflam.

Annual bluegrass (Poa annua L.) is a problematic weed in high maintenance turfgrass. Its lime green color contrasts that of desired turfgrass species, giving the turf a mottled appearance and disrupting color uniformity. Field experiments were conducted at Lake Ridge Country Club in Lubbock, TX on a hybrid bermudagrass fairway during the fall of 2009 to determine the efficacy of indaziflam for the pre- and postemergence control of annual bluegrass. Plots measured 1.5 x 1.5 m and were arranged in a randomized complete block design with four replicated treatments. Treatments were applied using a CO₂ backpack sprayer with XR8003VS nozzle tips and calibrated to deliver 304 L/ha at 276 kPa. Treatments were initiated on September 16, 2009 and consisted of indaziflam at 0.030, 0.040, 0.050, and 0.060 kg ai/ha; and prodiamine at 0.56 and 0.84 kg ai/ha. Visual estimates of percent annual bluegrass control and bermudagrass phytotoxicity were taken 1, 2, 4, 6, 8, 10, and 28 WAIT. Data were subjected to analysis of variance (ANOVA) and means were separated using Fisher’s Protected LSD at the 0.05 significance level. No bermudagrass phytotoxicity was recorded throughout the length of the trial regardless of treatment. Indaziflam treatments exhibited 100% annual bluegrass control 4 and 10 weeks after initial treatment (WAIT) regardless of application rate. Indaziflam applied at 0.040 kg ai/ha or greater still exhibited 100% control 28 WAIT, while applications of 0.030 kg ai/ha declined to 93%. Prodiamine treatments exhibited 91 to 96% control 4 WAIT and 95 to 96% control 10 WAIT regardless of rate. Control with prodiamine decreased to 25 to 38% 28 WAIT. Postemergence control of annual bluegrass increased as indaziflam rates increased. Indaziflam at 0.03 and 0.04 kg ai/ha exhibited 75% control while higher rates exhibited ≥ 93% 10 WAIT. No postemergence control was observed with prodiamine treatments.