Evaluation of Alternative Chemical Controls for Silvery-Thread Moss in Creeping Bentgrass Putting Greens.

Silvery-thread moss (Bryum argenteum Hedw.) is a common weed in creeping bentgrass (Agrostis stolonifera L.) putting greens, and alternative moss control strategies are needed.  Spot spray treatments of sodium bicarbonate (22.5 and 45 g a.i. L^-1), potassium bicarbonate (22.5 and 45 g a.i L^-1), and Mossbuster (ready-to-use, 1% essential oil) as well as broadcast treatments of sodium bicarbonate (55 and 110 kg a.i. ha^-1), potassium bicarbonate (4.8, 11.4, and 93.5 kg a.i. ha^-1), and carfentrazone-ethyl (Quicksilver, 0.09 kg a.i. ha^-1) were applied on 21 May, 4 Jun, 11 Sept., and 24 Sept. 2009 and moss severity and turf quality were assessed biweekly.  Differences in moss severity among treatments were significant on three dates.  Spot application of sodium bicarbonate (45 g a.i.·L^-1) and Mossbuster suppressed moss severity on two dates, whereas spot application of potassium bicarbonate (45 g a.i.·L^-1) suppressed severity on all three dates.  Sodium and potassium bicarbonate (22.5g a.i.L^-1, respectively) suppressed moss severity on one date.  Broadcast spray applications of sodium and potassium bicarbonate (55 and 11.4 kg a.i. ha^-1, respectively) were not effective, and all other bicarbonate broadcast applications were suppressive to moss on one date in 2009.  Quicksilver suppressed moss similar to spot spray bicarbonate applications and was effective on two dates.  Spot sprays of Mossbuster, the high rates of sodium and potassium bicarbonate were phytotoxic, as were both broadcast treatments of sodium bicarbonate and potassium bicarbonate at 93.5 kg a.i. ha^-1.  The highest concentration spot treatments of sodium and potassium bicarbonate, Mossbuster, and the highest broadcast rate of potassium bicarbonate required up to 14 days for turf to recover.  Bentgrass treated with sodium bicarbonate (110 kg a.i./ha) required up to eight days to recover.  Bicarbonate and essential oil products can reduce moss severity but rates and/or application methods may need to be optimized to avoid injury to turfgrass.