Dollar Spot Control In Creeping Bentgrass As Influenced by Fungicide Spray Volume and Application Timing

Abstract

Dollar spot (DS), caused by Sclerotinia homoeocarpa F. T. Bennett, can be a difficult disease to control in creeping bentgrass (Agrostis stolonifera L.). The objectives of this three-year field study were to: (i) assess the influence of two spray volumes (468 and 1020 liters of water per ha); and (ii) evaluate the impact of the presence or absence of dew at the time of application on the ability of chlorothalonil, propiconazole, and a tank mix of chlorothalonil and propiconazole to control DS in fairway-height creeping bentgrass. Chlorothalonil provided better DS control when applied to a dry canopy after 12:00 h, when compared to AM applications. Chlorothalonil generally provided better DS control when applied in 468 versus 1020 liters of water per ha; however, there were no rating dates when chlorothalonil provided more effective DS control when applied in 1020 liter/ha. On several 2004 rating dates, chlorothalonil applied in the AM with dew displaced provided better DS control than the AM application with dew present. The presence or absence of dew and the two spray volumes assessed did not affect the level of DS control provided by propiconazole or a tank mix of propiconazole and chlorothalonil. The amount of AM dew present in the canopy ranged between 982 and 2,548 liter/ha. Chlorothalonil performance likely was reduced as a result of being diluted or washed from foliar surfaces in the high spray volume or diluted by dew. Since both fungicides performed well when applied in 468 liters of water per ha, golf course managers can use the lower spray volume to save time, labor, and fuel.