Sand Topdressing Programming Effects On Anthracnose Disease of Annual Bluegrass Putting Green Turf.

Sand topdressing applied to annual bluegrass (Poa annua L. f. reptans [Hauskins] T. Koyama) turf during the summer can reduce the severity of anthracnose (caused by Colletotrichum cereale Manns). However, the effects of topdressing during spring and autumn on this disease are not well understood. A two-year field study was initiated in autumn 2010 to evaluate the effect of autumn, spring and summer topdressing with medium sand on anthracnose severity of annual bluegrass turf mowed at 2.8 mm. This trial was arranged as a 3 x 3 x 3 factorial in a randomized complete block design with 4 replications. Autumn and spring topdressing were applied at rates of 0, 1.2, or 2.4 L m^-2. Biweekly summer topdressing was applied at 0, 0.075 L m^-2 or 0.15 L m^-2. Autumn topdressing at 2.4 L m^-2 reduced disease severity on 5 of 7 rating dates in 2011 and all dates in 2012; whereas spring topdressing at 2.4 L m^-2 reduced disease severity on all dates in 2011 and 2012. Both autumn and spring topdressing at 1.2 L m^-2 reduced disease severity but less consistently and to a lesser extent than topdressing applied at 2.4 L m^-2. Biweekly summer topdressing did not affect anthracnose severity until mid-July 2012 when topdressing at 0.15 L m^-2 reduced disease severity compared to no summer topdressing. To date, interactions among autumn, spring, and summer topdressing have not been observed. Both autumn and spring topdressing can be effective management practices for suppressing anthracnose severity; however, spring topdressing provides a more consistent and long-term effect during the growing season.