Moss Control on Creeping Bentgrass Greens with Standard and Alternative Approaches

Moss is common on creeping bentgrass ( Agrostis stolonifera L.) putting greens, and more control options are needed. Spot treatment of sodium bicarbonate (44.2 g·L −1 ) was compared with broadcast sprays of carfentrazone-ethyl (50.5 or 101 g a.i./ha), chlorothalonil (8.2 or 12.8 kg a.i./ha) and a tank mixture of chlorothalonil, mancozeb, and thiram (8.2, 9.8, and 11.5 kg a.i./ha) in 2006 in Lemont, IL. Sodium bicarbonate suppressed moss growth equally as the conventional products. These results led to further experiments in 2008 in which moss suppression was evaluated within standard and alternative putting green management regimes in Manhattan, KS, and Lemont, IL. The standard approach included spring and fall applications of carfentrazone-ethyl (101 g a.i./ha) for moss control, biweekly applications of urea (46N–0P–0K) at 15 kg N/ha, and applications of chlorothalonil (8.2 kg a.i./ha) on a 14-day interval. Conversely, the alternative approach included spring and fall spot treatments of sodium bicarbonate (44.2 g·L −1 ) for moss control, biweekly applications of a natural organic fertilizer (8N–1P–3K) to provide nitrogen at 15 kg N/ha, and applications of chlorothalonil (8.2 kg a.i./ha) only when dollar spot reached a predetermined threshold level. Standard and alternative regimes were compared at both 3.2- and 4.0-mm mowing heights; synthetic and organic fertilizers applied alone without pest control approaches were included as controls. In Kansas and Illinois, moss coverage using the alternative management regime was not significantly different from that on greens managed using the standard regime. In Kansas, moss severity at a 3.2 mm was 1.6-fold higher than at the 4.0-mm height. In Illinois, sodium bicarbonate suppressed moss equivalently to the carfentrazone-ethyl treatment, and in the fertilizer-only controls, mowing at 3.2 versus 4.0 mm led to more moss coverage. These studies demonstrate that moss can be effectively suppressed on greens using spot applications of sodium bicarbonate and reduced moss encroachment is possible with higher mowing heights.