Effects of Timing and Dosage of Fungicide Applications On Control of Emerging Stem Rust Races (Puccinia graminis f. sp. tritici) in Winter Wheat

Abstract Stem rust on winter wheat ( Puccinia graminis f. sp. tritici ) has been found in many regions of Europe in recent years. With the emergence of resistance-breaking stem rust races, fungicide treatments are essential to secure yields as part of integrated pest management. In this study, the efficacy of fungicides which are not yet approved for the control of stem rust in Germany was investigated. The results show that effective control is possible with the three fungicides tested, Elatus Era, Fandango and Proline, whose efficacy varies with the time and dose of application. Seedling and field trials showed that mixtures of azoles (prothioconazole) with strobilurins (fluoxastrobin) as in the fungicide Fandango or carboxamides (benzovindiflupyr) as in the fungicide Elatus Era provide better control than solo treatments with prothioconazole as in the fungicide Proline. Curative treatments one, three and five days after inoculation of seedlings resulted in effective control of stem rust with all tested fungicides even at low doses. The timing of fungicide application proved to be a crucial factor, with treatments of seedlings closer to inoculation providing a better disease control, as confirmed in the field trials. Across all years, seed size as measured by thousand kernel weight was significantly higher than control in all treated variants in the field. There was no difference in grain yield. This research highlights the need for integrated pest management strategies, including decision support systems, to improve control while minimizing fungicide use through improved timing and ensuring sustainable crop protection.