Snow cover has variable effects on persistence of fungicides and their suppression of microdochium patch on amenity turfgrass

Abstract

Fungicides applied to turfgrass in temperate climates prior to snowfall are expected to suppress fungal diseases such as microdochium patch (Microdochium nivale) until infection conditions become unfavourable the following spring. However, mild winters with inconsistent snow cover may alter fungicide persistence and render the turf more susceptible to fungal infection. This study was conducted to determine the effect of snow cover on the persistence of the fungicides chlorothalonil and iprodione applied to creeping bentgrass (Agrostis stolonifera), maintained as a golf course fairway. The fungicides were applied 1 day prior to the first accumulating snowfall in Madison, Wisconsin, for four consecutive winters, beginning in 2009/10. Fungicide treatments were kept under continuous snow cover or maintained free of snow cover the entire winter to determine the effect of snow cover on fungicide persistence (2010/11 to 2012/13) and microdochium patch development in a controlled environment chamber (2009/10 to 2012/13). Iprodione concentration was not impacted by snow cover in 2010/11 but was reduced under snow cover relative to bare turf in 2011/12 and 2012/13. Chlorothalonil concentration was not impacted by snow cover in 2011/12 but was greater under snow cover in 2012/13. Microdochium patch severity in the controlled environment chamber was not impacted by snow cover with either fungicide in 2009/10 or 2011/12 but was slightly reduced under snow cover with both fungicides during 2010/11 and 2012/13. The majority of fungicide depletion occurred shortly after rainfall or snowmelt events, except in 2010/11 when both fungicides rapidly depleted during a warming trend without rainfall.

Suppression of Microdochium patch using rotations of mineral oil, sulfur, and phosphorous acid

“…Potential disadvantages would be the lack of complete disease suppression by 3-wk applications that may not meet golfer expectations (Walsh, 2005). Rainfall (Koch et al, 2015), microbial degradation (Magri & Haith, 2009), removal of leaf tissue (and with it the product), sorption of the products to the leaves and thatch (Sigler et al, 2003), and turfgrass metabolism of fungicides are all possible reasons for a decrease in fungicide effectiveness over time, and they may explain the frequent lack of Microdochium patch observed on plots receiving applications every 2 wk compared to some disease observed on plots that received treatments every 3 wk.…”

Identification and fungicide sensitivity of Microdochium chrysopogonis (Ascomycota, Amphisphaeriaceae), a new species causing tar spot of Chrysopogon zizanioides in southern China

“…Notably, compounds such as prochloraz, difenoconazole, propiconazole, metconazole, myclobutanil, tebuconazole and triticonazole have shown substantial antifungal efficacy against M. panattonianum , M. majus and M. nivale ( Wicks et al 1994 ; Debieu et al 2000 ; Glynn et al 2008 ; Mao et al 2023 ). Additionally, fungicide subgroups, including phenylpyrrole ( PP ) fungicides, such as fludioxonil, dicarboximides, such as iprodione and quinone outside inhibitors (QoIs), such as trifloxystrobin, have demonstrated noteworthy efficacy in the management of diseases induced by M. nivale ( Glynn et al 2008 ; Koch et al 2015 ; Aamlid et al 2017 ). Therefore, to promote effective control against tar spot of C. zizanioides , it is necessary to determine the sensitivity of the pathogen to fungicides.…”

Assessment of Temperature and Time Following Application as Predictors of Propiconazole Translocation in Agrostis stolonifera

“…Snow molds, such as Typhula blight ( Typhula incarnata and Typhula ishikariensis ) and Microdochium patch ( Microdochium nivale ), are the primary low-temperature diseases of amenity turfgrass around the world. , Control of snow molds in turfgrass is traditionally obtained with one or two fungicide applications in the fall shortly before snow cover, and in many cases, a mixture of fungicide-active ingredients is required to obtain adequate disease control. , The appropriate timing of these fungicide applications is essential for disease control and has been the source of considerable debate in recent years. Some turfgrass managers choose to apply fungicides well in advance of snowfall while the plant is still growing, which could leave the turf susceptible to snow mold development due to degradation of the fungicides . Others attempt to avoid fungicide degradation by applying fungicide immediately before snow cover arrives, though it is unclear whether the fungicides are absorbed and translocated within the plant at colder temperatures .…”