Fungicide strategies for Ramularia Leaf Spot control recommended in Uruguay and its residues in barley grains

Abstract

Ramularia leaf spot (RLS) is primarily managed by foliar fungicide spraying, which can result in residues in the grain. In recent years, increasing attention has been paid to the risks these residues pose to consumers. This study aimed to evaluate the efficacy of fungicide management used for RLS control and their fungicide residues in barley grain. Four different alternatives of fungicide mixtures: fluxapyroxad + pyraclostrobin + epoxiconazole; pyraclostrobin + epoxiconazole + chlorothalonil; prothioconazole + trifloxystrobin, and isopyrazam + azoxystrobin, in three spray timings: GS33, GS47 and GS33+GS47, were evaluated in five field experiments. An untreated and a fully protected treatment were included. Fungicide residues, disease severity, control efficacy, area under the disease progress curve, and plump grain yield were calculated. All fungicide strategies adhered to food safety, complying with the Maximum Residue Limits established by Codex and the European Union. Effectiveness varied based on RLS development, application time, and number of applications. Fungicide treatments applied at GS33+GS47 were the most effective as the highest severity levels were observed at the stage after GS47 under the conditions studied. Plump grain yield only showed minimal differences in the late epidemic. The study emphasized the low risk of fungicide presence in grains, favoring efficacy when selecting RLS management options. Any changes in management or regulations should be carefully reviewed to maintain findings. The research underscored the compatibility of recommended fungicide treatments with food safety standards, highlighting the balance between disease control efficacy and consumer safety.