Investigating Mechanisms of Dollar Spot Reduction Through Light-Weight Rolling On Creeping Bentgrass Putting Greens.

Dollar spot (Rutstroemia floccosum syn. Sclerotinia homoeocarpa F.T. Bennet) is one of the most important diseases to affect golf course turf grasses in the United States.  A 3-yr study to investigate the effects of light-weight rolling on the suppression of dollar spot was conducted with the objective of elucidating disease reduction mechanisms. Creeping bentgrass (Agrostis stolonifera L.) plots subjected to daily (5 days week^-1) rolling treatments (1x a.m., 1x p.m., 2x a.m.) showed significant disease reductions when compared to a non-rolled control. Treatments rolled in the p.m. (after dew and guttation fluid dissipated) exhibited similar disease reductions as treatments rolled in the morning.  The 2x day^-1 treatment exhibited significantly less dollar spot than all other treatments (P < 0.05), as well as significantly higher rootzone volumetric water content (VWC) than the control.  Microbial populations were evaluated via phospholipid fatty acid (PLFA) analysis in order to investigate potential effects of rolling on microbial abundance and dynamics in the upper rootzone. Rolled treatments exhibited significant increases in PLFA abundances related to common bacteria, as well as a general trend towards increased total bacterial biomarker abundance when compared to the non-rolled control. Results indicate added physical and biological effects of rolling on turfgrass, which may be contributing to dollar spot disease suppression.