Anthracnose severity influenced by cultural management of annual bluegrass putting green turf.

摘要

Anthracnose (Colletotrichum cereale Manns sensu lato Crouch, Clarke, and Hillman) has become a devastating disease of annual bluegrass [Poa annua L. f. reptans (Hausskn) T. Koyama] putting green turf over the past 15 years. Factors responsible for the increased incidence and severity of anthracnose epiphytotics are not well understood, although speculation has focused on the influence of cultural practices on this disease. Six field trials were conducted from 2003 to 2007 to evaluate effects of cultural practices on anthracnose severity of annual bluegrass putting green turf in factorial arrangements. Nitrogen fertilization, mowing height and topdressing practices provided the most consistent and greatest influence on disease. Nitrogen applied from May through September at 4.9 kg ha-1 every 7 d reduced anthracnose severity 5 to 24% compared to the same rate applied every 28 d. Mowing at 3.6 mm reduced disease 3 to 21% compared to 2.8 mm, while 3.2 mm had intermediate disease severity. Mowing frequency (7 vs. 14 times wk-1) had little effect on anthracnose. Sand topdressing applied every 7 d at 0.3 L m-2 and 14 d at 0.6 L m-2 reduced anthracnose severity compared to no topdressing or similar rates applied less often, although greater rates applied less often (i.e., 21 d at 1.2 L m-2) provided comparable results. Topdressing with sub-angular sand occasionally reduced anthracnose more than rounded sand. Lightweight rolling every other day reduced disease severity 5 to 6% under moderate disease pressure. The plant growth regulators trinexapac-ethyl, mefluidide and ethephon had inconsistent effects on anthracnose severity; however these materials typically did not increase disease and in some cases reduced it. For example, the combination of 7 d N fertilization, mefluidide and trinexapac-ethyl application occasionally reduced disease more than each factor alone. Also, trinexapac-ethyl applied at shorter intervals (7 vs. 14 d) and increased rate (0.08 vs. 0.05 kg a.i. ha-1) reduced anthracnose when disease severity was high. Cultural practices that may wound turf (e.g., verticutting and brushing) had little effect on anthracnose. These results provide the foundation for the development of best management practices to minimize anthracnose severity of annual bluegrass putting green turf.