Effect of Nitrogen Source on Silvery-thread Moss on a Creeping Bentgrass Putting Green

Silvery-thread moss (Bryum argenteum Hedw.) is a common weed in creeping bentgrass (Agrostis stolonifera L.) putting greens. Low N fertility has been associated with increased moss severity, though the effect of N source on moss is unknown. Recent studies suggest that N source may be important in influencing moss encroachment. Our objective was to evaluate the response of silvery-thread moss to differing N sources on a ‘Penncross’ creeping bentgrass putting green. In 2009 and 2010, liquid urea (i.e., urea dissolved in water), granular urea, isobutylidene diurea (IBDU), and organic N were used to deliver N at 0.3 lb/1,000 ft² biweekly for a total of 4.3 lbs/1,000 ft² annually. According to mean area under the curve (AUC) values over 2009 and 2010, fertilizing the green with liquid urea resulted in a 147% to 155% increase in moss coverage compared to all other N sources. Application of liquid urea on creeping bentgrass infested with silvery-thread moss has the potential to increase its spread.