Effect of Mowing Height On Preemergence Herbicide Efficacy for the Control of Crabgrass Species.

Field trials were conducted at Pine Hills Golf Course in Winder, GA on common bermudagrass during the summer of 2013. Plots (1.5 x 3.0 m) were arranged in a 2 x 15 factorial arranged in a split block design with three replications. The main factor was mowing height (1.3 or 5.1 cm) and the sub-factor was preemergence herbicide. Herbicide treatments were initiated on March 8, 2013 and consisted of indaziflam [0.035, 0.053, 0.018 followed by (fb) 0.018, and 0.026 fb 0.026 kg ai ha^-1], prodiamine (1.68 and 0.84 fb 0.84 kg ai ha^-1), pendimethalin (3.36 and 1.68 fb 1.68 kg ai ha^-1), dithiopyr (0.56 and 0.28 fb 0.28 kg ai ha^-1), oxadiazon (4.5 and 2.25 fb 2.25 kg ai ha^-1), and sulfentrazone + prodiamine (1.26 and 0.64 fb 0.64 kg ai ha^-1). Sequential herbicide applications were made on May 3, 2013. Treatments were applied with a CO₂ backpack sprayer calibrated to deliver 281 L ha^-1 at 276 kPa. An untreated control was added for comparison. Percent large crabgrass cover was visually assessed biweekly starting mid-April when large crabgrass germination was observed in the untreated check plots. Large crabgrass control was calculated on a scale relative to the untreated check within each replication, where 0 equaled no large crabgrass control and 100 equaled complete control. Mowing height did not influence herbicide efficacy except when indaziflam was applied at 0.035 and 0.018 fb 0.018 kg ai ha^-1. On July 26, 2013, large crabgrass control with indaziflam (0.035 or 0.018 fb 0.018 kg ai ha^-1) was 72 and 60%, respectively, in 1.3 cm bermudagrass and 88 and 73%, respectively, in 5.1 cm bermudagrass. Indaziflam at 0.053 and 0.026 fb 0.026 kg ai ha^-1 resulted in 88 and 75% large crabgrass control by July 26, 2013, regardless of bermudagrass height. The least amount of large crabgrass control (59 to 64%) by July 26, 2013 was observed in response to oxadiazon at 2.25 fb 2.25 kg ai ha^-1. All other treatments resulted in 89 to 100% large crabgrass control by July 26, 2013, regardless of bermudagrass height.