Dollar Spot Control Using Biofungicides and Conventional Fungicides Applied Based on the Smith-Kerns Dollar Spot Model in Creeping Bentgrass Fairway Turf.

Integrated pest management principles typically include use of action thresholds, although thresholds are infrequently utilized for turfgrass diseases due to our inability to preventively identify biological indicators of disease.  Biofungicides applied for dollar spot control have provided inconsistent results, particularly applied alone.  However, integration of biofungicides with conventional fungicides applied based on model thresholds may enhance disease control and minimize applications of conventional fungicides.  The objectives of this study were to determine whether fungicides applied based on the Smith-Kerns dollar spot model could provide comparable disease control as conventional 21-d fungicide timings, and whether biofungicides could help improve disease control of fungicides applied at high risk forecast model thresholds on creeping bentgrass fairway turf throughout the season.  Treatments were arranged in a 4 × 4 factorial with main effect factors being fungicide application interval and biofungicide.  Fungicide application intervals consisted of Smith-Kerns dollar spot forecast model risk action thresholds of 30% (high risk) or 20% (moderate risk), 21-d calendar based, or a non-fungicide treated control.  Biofungicides evaluated included TurfShield Plus, Companion, Rhapsody and a non-biofungicide control. Conventional fungicide application intervals initiated for 21-d calendar-based fungicide treatment and 20% risk action threshold treatments on 14 May, and 30% risk action threshold on 1 June.  Model-based treatments were reapplied when specified risk thresholds were reached; although re-applications were withheld for 21-d following fungicide application regardless of model forecast.