EFFECTS OF MOWING PRACTICES AND DEW REMOVAL ON FUNGICIDE EFFICACY FOR DOLLAR SPOT CONTROL

Open Access
Author:
Delvalle, Tanner Clinton
Graduate Program:
Agronomy
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Peter Landschoot, Thesis Advisor
Keywords:
  • Fungicides
  • Dew Removal
  • Mowing
  • Cultural Practices
  • Dollar Spot
  • Efficacy
  • Golf
  • Disease
Abstract:
Dollar spot (Sclerotinia homoeocarpa F.T. Bennett) is a severe disease problem on creeping bentgrass (Agrostis stolonifera L.) fairways in the northeastern United States. Although dollar spot can be managed with fungicides, golf course managers attempt to limit fungicide use on fairways due to cost considerations and concerns over fungicide resistance. The objective of this study was to evaluate the effects of dew removal and mowing frequency on fungicide performance for dollar spot control. In 2009 and 2010, a factorial experiment involving daily dew removal or no dew removal, mowing frequency (2, 4, and 6 d wk-1), and fungicides (chlorothalonil, propiconazole, and iprodione) was conducted on creeping bentgrass and annual bluegrass (Poa annua L.) maintained as a golf course fairway. Fungicides were applied once at the beginning of each test, and daily dew removal and mowing treatments were performed between 0700 and 0800 h. Dollar spot was assessed by counting infection centers in each plot. Area under the disease progress curve data showed that daily dew removal resulted in fewer dollar spot infection centers compared to not removing dew during late summer 2009 and 2010 for all mowing frequency and fungicide treatments. As mowing frequency increased from 2 to 6 d wk-1, dollar spot decreased when both dew removal and no dew removal treatments were included in the data analyses. However, when data analyses included only treatments in which dew was removed daily, differences in dollar spot incidence among mowing frequencies were not detected at P ≤ 0.05 using Tukey’s Honestly Significant Difference Test. This finding suggests that the effect of mowing frequency on dollar spot suppression is related to dew removal. Dew removal in iprodione-treated plots mowed 4 d wk-1 during late summer 2009 provided up to 10 additional days to reach a 15-infection-center plot-1 threshold level compared to iprodione plots in which dew was not removed. Similar trends were noticed for propiconazole and chlorothalonil treatments at certain times during the test. The number of days required for infection centers to reach the threshold varied with fungicide treatment, mowing frequency, and season. Results of this study demonstrate that fungicide performance for dollar spot control can be extended when daily dew removal is employed, and in some cases, when mowing frequency is increased on dew-covered turf. However, benefits of dew removal practices on fungicide performance can vary with weather conditions, fungicide, threshold level, and possibly other factors.