Impact of cultural management on anthracnose severity of annual bluegrass putting green turf

Abstract

Anthracnose (Colletotrichum cereale Manns) has become an increasingly destructive disease of annual bluegrass (ABG) [Poa annua L. f. reptans (Hausskn) T. Koyama] putting green turf over the past two decades. Cultural management to enhance the playing surface characteristics of putting greens are thought to enhance abiotic stress and predispose turf to anthracnose. Three field trials conducted from 2006 to 2008 evaluated the effects of irrigation, equipment traffic and lightweight rolling, and sand topdressing on anthracnose severity of ABG turf mowed at 3.2 mm. Severe deficit irrigation [40% replacement of reference evapotranspiration (ETo)] increased anthracnose severity during the study. Anthracnose was less severe under greater irrigation quantity. However, irrigating at 100% ETo resulted in disease severity similar to irrigation at 40% ETo by the end of 2006 and 2008. Irrigation to replace 80% ETo typically resulted in the least amount of disease and the best turf quality. Plots receiving turning of mowers and lightweight rollers as well as clean-up mowing (representing the putting green perimeter) had lower disease severity compared to center plots on 6 of 13 dates in 2007 and 2008. Additionally, lightweight rolling reduced anthracnose 2 to 13% compared to non-rolled turf in 2007 and 2008; the heavier sidewinder roller treatment had less disease than the triplex mounted vibratory roller treatment on 4 of 13 rating dates. Initially, turf receiving sand topdressing (0.3 L m-2 wk-1) had a small increase in disease compared to non-topdressed turf during 2007; however, disease decreased as much as 9% by August 2007 and again in 2008 on topdressed plots. Surprisingly, turf receiving foot traffic (5 d wk-1, ~200 rounds d-1) had as much as 27% lower disease severity than non-trafficked turf. This effect was independent of the level of sand topdressing during 2007 and 2008. The treatment combination of weekly topdressing and frequent foot traffic resulted in the best turf quality by the end of both seasons. Overall, the results of these three studies indicate that best management practices should be an integral component of a disease control program intended to reduce anthracnose severity on ABG putting green turf.