Comparison of Preventive Vs. Curative Fungicide Spray Programs for Dollar Spot Control On Fairway-Height Creeping Bentgrass.

Creeping bentgrass (Agrostis stolonifera L.) is an important turfgrass species in the cool and transitional climatic zones, particularly on golf course greens and fairways.  Among the pests that can affect bentgrass, dollar spot disease (Sclerotinia homoeocarpa F. T. Bennett) is one of the most significant and currently requires biweekly fungicide applications to maintain disease severity at acceptable levels.  This frequent use of fungicides is becoming increasing costly and warrants research into finding ways to reduce the number of fungicide applications.  The objective of this study was to compare the number of curative vs. preventative fungicide applications to control dollar spot when varying chemicals and disease thresholds are used.  For this study, chlorothalonil and propiconazole were sprayed preventatively every two weeks and curatively when disease severity reached 1% and 10% within plots.  Trinexapac-ethyl was also applied within treatments to examine possible fungicidal and/or synergistic activity.  For the first year, disease severity ranged from an average of 0-50.0% with all fungicide treatments being significantly different than the unsprayed controls during periods of higher disease pressure.  Current data indicates fewer applications can be made with a 10% disease threshold as compared to a 1% threshold or a regular biweekly spray regime.