Leaching and surface runoff after fall application of fungicides on putting greens

Abstract

AbstractMany greenkeepers and authorities are concerned about the environmental risks resulting from pesticide use on golf courses. We studied leaching and surface runoff of fungicides and metabolites for two winter seasons after fall application of boscalid, pyraclostrobin, prothioconazole, trifloxystrobin, and fludioxonil in field lysimeters at NIBIO Landvik, Norway. The applications were made on creeping bentgrass greens (5% slope) that had been established from seed or sod (26‐mm mat) on USGA‐specification. root zones amended with Sphagnum peat or garden compost, both with 0.3–0.4% organic carbon in the root zone. The proportions of the winter precipitation recovered as surface and drainage water varied from 3 and 91% in 2016–2017 to 33 and 55% in 2017–2018 due to differences in soil freezing, rainfall intensity, and snow and ice cover. Detections of fungicides and their metabolites in drainage water were mostly within the environmental risk limits (ERLs) for aquatic organisms. In contrast, concentrations in surface runoff exceeded ERLs by up to 1,000 times. Greens established from sod usually had higher fungicide losses in surface runoff but lower losses in drainage water than greens established from seed. Presumably because of higher microbial activity and a higher pH that made prothioconazole‐desthio more polar, fungicide and metabolite losses in drainage water were usually higher from greens containing compost that from greens containing peat. Leaching of fungicides and metabolites occurred even from frozen greens. The results are discussed in a practical context aiming for reduced environmental risks from spraying fungicides against turfgrass winter diseases.