According to IPM principles, pesticides should be used only when other measures do not provide sufficient control of the harmful organism. One situation where adequate control is difficult is when golf courses are infected with Microdochium nivale. In such cases, it is important to use efficient fungicides with few environmental impacts. This project focused on leaching and surface runoff of fungicides and their metabolites from greens after application in late autumn.
A field trial was conducted during winter 2016-17 and 2017-18 at Landvik, Norway. The plots had 5% slope and a turf cover of creeping bentgrass. The trial had four blocks and two factors, each with two levels:
In both years, Delaro (prothioconazole+trifloxystrobin) and Signum (boscalid+ pyraclostrobin) were sprayed in late October and Medallion (fludioxonil) in early November. Factor 1: Organic amendment in the sand-based (USGA) rootzone: Factor 2: Turf age / thatch thickness 1.Sphagnum peat, loss on ignition 1.2 % OM, pH 5.5 A. Green seeded in May 2016 2.Garden compost, loss on ignition 1.0 % OM, pH 6.5 B. Green established in May 2016 using sand-based sod, (25 mm thatch) Applications were followed by collection of leachate and runoff until snowmelt/soil thaw around 1 April. During winter 2016-17, the mostly unfrozen greens had high infiltration rates: 91% of 601 mm precipitation from the first fungicide application to the last sampling was collected as drainage water and only 3 % as runoff. Winter 2017-18 had 948 mm precipitation, and freeze/thaw cycles on frozen greens resulted in ice cover. In this case, 55 and 33 % of precipitation was collected as drainage water and surface runoff, respectively. Fungicide detections in drainage water were mostly very low; the Norwegian Environmental Risk Level (ERL) was exceeded slightly only for prothioconazole-desthio. In contrast, the ERL for many fungicides and/or their metabolites was exceeded up to 1000 times in surface water, notably in 2017-18. The highest concentrations were found during the first week after spraying and after snowmelt/soil thaw. Because of the thatch layer, concentrations in runoff were usually higher, but concentrations in drainage lower, on sodded than on seeded greens.
The project highlights the importance of keeping wide buffer zones to open water and avoiding surface runoff by maintaining high infiltration rates. This was communicated to more than 70 industry representatives at the project’s final international seminar in Oslo on 7 March 2019.
