Early Curative Dollar Spot Control in Creeping Bentgrass as Influenced by Fungicide Spray Volume and Application Timing

Abstract

The importance of spray volume and application timing of a fungicide targeting dollar spot (Sclerotinia homoeocarpa F. T. Bennett) has been investigated, but with conflicting results. The objectives of this field study were to assess the influence of two spray volumes (468 and 935 liters water/ha) and two application timings (AM to a canopy wet with dew versus PM to a dry canopy) for fungicides targeting dollar spot curatively. Chlorothalonil (8.5 kg a.i./ha), propiconazole (0.5 kg a.i./ha), and a tank‐mix of chlorothalonil + propiconazole were compared on fairway height stands of ‘Crenshaw’ (2007 and 2008), ‘Backspin’ (2008), and ‘Providence’ (2009) creeping bentgrass (Agrostis stolonifera L.). There were no spray volume differences in 2007 or 2009. In 2008 in Crenshaw, there was less dollar spot in chlorothalonil‐treated plots using the low versus high spray volume, but the opposite occurred in Backspin. Less dollar spot developed in propiconazole‐treated plots subjected to the low versus high spray volume in Crenshaw in 2008. Higher levels of dollar spot developed in plots treated with propiconazole in the PM compared to the AM in 2009. The tank‐mix of chlorothalonil + propiconazole was unaffected by spray volume or application timing at all sites. The preponderance of data indicated that the curatively applied fungicides generally provided similar levels of dollar spot control at the two spray volumes and application timings evaluated.

Early Curative Fungicide Applications Provide Disease Control on Fairway-height Creeping Bentgrass

“…In a separate study, Cropper's (5) field experiments suggested that an early curative program performed better than a curative program based on an action threshold of 20% disease severity, although those curative approaches were not directly compared in the same experiment. Pigati et al (10) evaluated application volume and timing (AM vs. PM) as well as product efficacy under early curative conditions but did not compare an early curative program to alternative timing approaches. In limited testing in Indiana, a spray threshold of <1% damage provided acceptable dollar spot control on fairway‐height creeping bentgrass, which was not the case with a 3 to 4% threshold (8).…”