The influence of water pH on efficacy of fungicides for turf disease control

Abstract

AbstractFungicides are often mixed with water and applied as a dilute spray for controlling diseases on golf course turf. Although published reports show that water quality can influence the performance of certain herbicides, evidence of similar effects on fungicide efficacy is weak and largely anecdotal. The objective of this research was to investigate the influence of water pH on efficacy of fungicides commonly used against dollar spot, a problematic disease of creeping bentgrass (Agrostis stolonifera L.). Here, three fungicides (metconazole, thiophanate‐methyl, and iprodione) were mixed with water stabilized at three pH levels (pH = 5.0, 7.0, and 9.0) in in vitro and field experiments. A time factor was also considered (i.e., the time between mixing and application, where T0 indicated that the fungicides were applied immediately after mixing and T24 indicated that the fungicides were applied 24 h after mixing). Field experiments revealed little or no difference in fungicide performance when mixed in acidic (pH = 5.0), near‐neutral (pH = 7.0), and alkaline (pH = 9.0) water. The time factor was also not significant for all fungicides and water pH levels. Results from in vitro work on culture media supported field observations: few differences in pathogen growth were observed for pH and time factors. Although tank‐mixing products to neutralize water pH may be important, our results support the null hypothesis that the carrier water pH does not influence the efficacy of these three fungicides for controlling dollar spot on creeping bentgrass.