Regulation with Trinexapac-ethyl and Dew Removal at the Time of Fungicide Application Did Not Influence Dollar Spot Control

Abstract

Dollar spot, caused by Sclerotinia homoeocarpa F.T. Bennett, is an important disease of creeping bentgrass (Agrostis stolonifera L.) on golf courses in the northern United States. Canopy moisture in the form of dew plays an important role in the development of dollar spot and routine displacement has been shown to reduce disease severity. The use of plant growth regulators (PGRs) is a common management practice for maintaining creeping bentgrass fairways, but their influence on dollar spot is unclear. The objective of this field study was to elucidate the influence of dew removal at the time of fungicide application on dollar spot control in creeping bentgrass regulated by trinexapac-ethyl (TE). Main factors in the study included three dew removal strategies (non-treated, dew removed–mowed, and dew removed–not mowed) before the application of four fungicide treatments (non-treated, chlorothalonil, propiconazole, and iprodione). All fungicide treatments were applied once to turfgrass previously treated with TE or not treated. The presence or absence of dew at the time of fungicide application generally had no influence on fungicide performance with respect to dollar spot control. Based on the results of this study, dew removal before the application of fungicides targeting dollar spot is unnecessary. Applications of TE before fungicides reduced dollar spot severity in some cases, but reductions in symptom expression were limited and did not result in markedly improved dollar spot control.