Effects of Dew Removal and Trinexapac-ethyl on Fungicide Efficacy for Dollar Spot Control

Open Access
Huang, Yu
Graduate Program:
Master of Agriculture
Document Type:
Master Thesis
Date of Defense:
November 06, 2012
Committee Members:
  • John Edward Kaminski Iii, Thesis Advisor
  • Peter Landschoot, Thesis Advisor
  • Wakar Uddin, Thesis Advisor
  • turfgrass
  • dollar spot
  • dew removal
  • trinexapac-ethyl
Dollar spot, caused by the pathogen Sclerotinia homoeocarpa F.T. Bennett, is a disease of all turfgrass species and is considered the most economically important disease on golf courses. Many cultural and chemical management practices are necessary to reduce disease symptoms. Canopy moisture (e.g., leaf wetness) plays an important role in the development of dollar spot and routine removal of dew has been shown to reduce disease severity. The effect of canopy moisture on fungicide efficacy at the time of fungicide application, however, is not well understood. In addition to management practices directly related to the reduction of dollar spot, other inputs like the application of plant growth regulators are common to golf courses for maintaining high quality turf. Trinexapac-ethyl (TE) is one of the most common PGRs used on golf courses, but its influence on dollar spot is unclear. The objective of this field study was to elucidate the influence of dew removal methods at the time of fungicide application on dollar spot control within turfgrass regulated by TE. Field studies were initiated at the Joseph Valentine Turfgrass Research Center on a mature ‘Penneagle’ creeping bentgrass (Agrostis stolonifera L.) fairway. Main factors in the study included three dew removal strategies (untreated, rolled and mowed) prior to the application of fungicides (untreated, chlorothalonil, propiconazole and iprodione). All treatments were applied to turfgrass previously treated with TE treatments (untreated and TE). Dollar spot infection centers (DSIC) and area under the disease progress curve data were analyzed using the PROC MIXED procedure in SAS. The presence or absence of dew at the time of fungicide application had no influence fungicide efficacy. The effect of regulation by TE on fungicide-treated turf had little influence on dollar spot severity. However, the effect of regulation on non-fungicide treated turf resulted in a significant reduction in DSIC. Based on the results of this study, dew removal prior to the application of fungicides in the morning is an unnecessary step and does not influence fungicide efficacy. Although TE had little influence on disease severity where fungicides were applied, its use in areas where fungicide applications are restricted or too cost prohibitive may provide a small, but beneficial reduction in dollar spot.