Best Management Practices for Anthracnose on Annual Bluegrass.

Anthracnose disease of annual bluegrass [Poa annua L. f. reptans (Hausskn) T. Koyama] (ABG)] caused by Colletotrichum cereale Manns can be suppressed by increased N fertilization, mowing height, and sand topdressing. The relative importance of these factors on anthracnose severity and ball roll distance (BRD) on ABG putting green turf was evaluated in a 3-yr field study in North Brunswick, NJ. A 2 x 2 x 2 factorial of mowing height (2.3 and 3.2 mm), N fertility (100 and 200 kg ha^-1 yr^-1), and sand topdressing (46 and 98 Mg ha^-1 yr^-1 in 2012; 37 and 81 Mg ha^-1 yr^-1 during 2013 and 2014) was arranged in a split-split-plot design. The greatest reduction in disease severity was achieved with the practice of applying greater N fertilization (200 kg ha^-1) compared to the practices of higher mowing (3.2 mm) or greater sand topdressing (81/98 Mg ha^-1). Acceptable disease suppression without fungicides occurred during moderate anthracnose epidemics in 2012 and 2014 (≤36 and 35% average turf area infested, respectively) when increased N fertilization was combined with higher mowing and greater sand topdressing. No treatment produced acceptable disease suppression during the severe epidemic of 2013 (≤76% average turf area infested). Under lower mowing (3.2 mm), BRD was acceptable on 91 to 96% of observation dates and accordingly was less affected by greater N fertilization. Not surprisingly, BRD was often unacceptable (< 2.9 m) under higher mowing, especially when combined with greater N fertilization. Thus, when adjustments in turf management practices are needed to increase BRD, lowering the mowing height would provide the desired enhancement and the least risk for increasing anthracnose, especially if greater N fertilization and increased topdressing are also practiced.