Anthracnose Disease on Annual Bluegrass as Influenced by Spring and Summer Topdressing

摘要

Sand topdressing annual bluegrass [Poa annua L. f. reptans (Hausskn) T. Koyama] (ABG) turf during the summer (SU) can reduce the severity of anthracnose disease, caused by Colletotrichum cereale Manns, but the effect of spring (SP) topdressing warrants further research. A 2-yr field study evaluated the effect of SP and SU topdressing on anthracnose severity of ABG maintained at 3.2-mm on a sandy loam in North Brunswick, NJ. Factors of SP (0, 1.2, and 2.4 L ma?’2 yra?’1) and SU (0, 0.525, 1.05, 2.1, and 4.2 L ma?’2 yra?’1) topdressing rate were arranged as a 3 ?— 5 factorial. Increasing SP rate reduced the area under disease progress curve (AUDPC) linearly in both years, whereas increasing SU rate reduced AUDPC linearly in 2009 but quadratically in 2010. Maximum AUDPC reduction was predicted at a lower total topdressing rate (2.4 and 2.63 L ma?’2 yra?’1 during SP and SU, respectively) in 2010 than 2009. Unlike AUDPC data, pooled disease severity data indicated that SP interacted with SU topdressing, and by late 2010, a SU topdressing rate as low as 2.1 L ma?’2 yra?’1 (at the greatest SP rate) maximized disease suppression. However, incorporation of sand applied at 2.1 and 4.2 L ma?’2 yra?’1 was often delayed, resulting in excess sand on the surface, whereas lower SU rates (0.525 and 1.05 L ma?’2 yra?’1) readily incorporated into the turf. This research indicates that SP topdressing can be used to reduce the rate of SU topdressing needed to suppress anthracnose but may not eliminate the need for SU topdressing to maximize disease suppression.