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

Several approaches for timing curative fungicide applications for control of dollar spot were compared on creeping bentgrass managed under fairway conditions. The efficacy of curative control of dollar spot depended on the action threshold selected. The “≥1%” curative treatment, in which applications were made when dollar spot severity in those plots averaged ≥1% (minimum spray interval 14 days), reduced fungicide usage by 30+% and generally provided equivalent or nearly equivalent disease control, as compared to a biweekly preventive program. The use of an action threshold of ≥10% disease severity reduced fungicide usage further but resulted in substantially less disease control than the preventive program. Based on our results, on creeping bentgrass fairways, golf course superintendents may be able to reduce fungicide usage by applying an effective fungicide when an early curative action threshold (such as 0.5% or 1%) is reached, with a minimum of two weeks between applications. The growth regulator trinexapac-ethyl had little impact on disease severity and minimal effect on the number of fungicide applications called for in the different curative programs tested.