Combined Effects of Topdressing, Cultivation, and Carfentrazone-Ethyl on Silvery-Thread Moss Infestation.

Carfentrazone-ethyl can reduce the competitiveness of silvery-thread moss (Bryum argenteum Hedw.) in putting greens; however, long-term control may be difficult when relying solely on herbicide applications. Therefore, the objectives of our study were to evaluate the combined effects of topdressing, cultivation, and carfentrazone-ethyl on silvery-thread moss control in a putting green. A randomized complete-block design with a split-plot treatment structure was used to evaluate twenty-four treatment combinations on a ‘Penncross’ creeping bentgrass putting green maintained at 3 mm. Topdressing was the whole plot treatment factor with two levels, bi-weekly or bi-annually. The split plot contained a 2 (with- or without herbicide) x 6 (cultivation technique) factorial. Bi-weekly topdressing applications were applied at 0.4 L m^-2 May through September. Bi-annual topdressing was applied at 0.8 L m^-2 in the spring and fall after cultivation treatments were performed. Carfentrazone-ethyl was applied at 111 g a.i. ha^-1 one week before and after cultivation treatments were applied in the spring and fall. Cultivation treatments included untreated, verti-slicing, and four aerficiation regimes using 0.95 cm or 1.27 cm tines, both at high and low surface disruptions. The topdressing, cultivation, and carfentrazone-ethyl treatments were applied in the spring and fall for two consecutive years. Cover data from the 1 x 1.2 m plots were recorded using a grid with 330 intersections. Change in moss cover was determined by comparing subsequent grid counts to those at trial initiation. Cover data was recorded each spring and fall before cultivation treatments were administered. Herbicide was highly significant (P<0.0001) at every rating date. On average, a 50% reduction was observed in plots receiving carfentrazone-ethyl compared to those not receiving the herbicide. Cultivation was significant (P<0.05) on several rating dates. Plots receiving any cultivation technique had 25% less moss compared to the untreated. Topdressing had no effect on moss cover.