Septoria tritici blotch (STB; Zymoseptoria tritici) is the most important leaf disease of wheat in Northern and Western Europe. The problem of fungicide resistance in Z. tritici populations is challenging future control options. In order to investigate differences in azole performances against STB, 55 field trials were carried out during four seasons (2015-2018). These trials were undertaken in ten different countries across Europe covering a diversity of climatic zones and agricultural practices. During all four seasons, four single azoles (epoxiconazole, prothioconazole, tebuconazole and metconazole) were tested. Increasing variability in the performances of these azoles against STB was observed across Europe. The efficacy of the tested azoles varied considerably across the continent and between countries. The shifts in disease control from these commonly used azoles were confirmed by increasing EC 50 values for epoxiconazole, prothioconazole-desthio and metconazole. The sensitivity towards tebuconazole remained relatively low across the four years. The frequencies of CYP51 mutations varied substantially across Europe, with a clear pattern of significantly decreasing frequencies of D134G, V136A and S524T in the local Z. tritici populations from west to east. In contrast, no major differences were seen for CYP51 mutations V136C, A379 and I381V. The four azoles showed different levels of cross-resistance, which again depended on specific CYP51 mutations. Across the four seasons, the single azoles increased the yields between 9 and 11% on average.

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Keywords: Acid, 2,4-dichlorophenoxy acetic acid (2,4-D), controlled release, ring-opening polymerization of β-butyrolactone, SEC, 1 H-NMR, ESI-MS characterization of oligomers, assessment of the herbicide effectiveness.Abstract: A novel herbicidal controlled release formulation composed of (2,4-dichlorophenoxy) acetic acid (2,4-D) chemically bonded to biodegradable (R,S)-3-hydroxybutyric acid oligomers was investigated. The synthesis of (R,S)-3-hydroxy butyric acid oligomers was carried out via the ring opening polymerization of β-butyrolactone initiated by 2,4-dichlorophenoxy acetic potassium salt in the presence of complexing agents. The formed oligomers were characterized by size exclusion chromatography, proton magnetic resonance and electrospray mass spectrometry in order to fi nd out their molar mass distribution and molecular structures. An assessment of biological effectiveness of the obtained herbicidal formulation was carried out in the greenhouse vs. Sinapis alba var. Nakielska. A promotion of the controlled release formulation with decreased water solubility and with low vapor pressure of the active ingredient, instead of traditional formulations of 2,4-dichlorophenoxy acetic acid may help to ensure a greater safety for workers and reduce the risk of dissemination of the active ingredient in the soil profi le.

Septoria tritici blotch (STB; Zymoseptoria tritici) is a severe leaf disease on wheat in Northern Europe. Fungicide resistance in the populations of Z. tritici is increasingly challenging future control options. Twenty-five field trials were carried out in nine countries across Europe from 2019 to 2021 to investigate the efficacy of specific DMI and SDHI fungicides against STB. During the test period, two single DMIs (prothioconazole and mefentrifluconazole) and four different SDHIs (fluxapyroxad, bixafen, benzovindiflupyr and fluopyram) along with different co-formulations of DMIs and SDHIs applied at flag leaf emergence were tested. Across all countries, significant differences in azole performances against STB were seen; prothioconazole was outperformed in all countries by mefentrifluconazole. The effects also varied substantially between the SDHIs, with fluxapyroxad providing the best efficacy overall, while the performance of fluopyram was inferior to other SDHIs. In Ireland and the UK, the efficacy of SDHIs was significantly lower compared with results from continental Europe. This reduction in performances from both DMIs and SDHIs was reflected in yield responses and also linked to decreased sensitivity of Z. tritici isolates measured as EC50 values. A clear and significant gradient in EC50 values was seen across Europe. The lower sensitivity to SDHIs in Ireland and the UK was coincident with the prevalence of SDH-C-alterations T79N, N86S, and sporadically of H152R. The isolates’ sensitivity to SDHIs showed a clear cross-resistance between fluxapyroxad, bixafen, benzovindiflupyr and fluopyram, although the links with the latter were less apparent. Co-formulations of DMIs + SDHIs performed well in all trials conducted in 2021. Only minor differences were seen between fluxapyroxad + mefentrifluconazole and bixafen + fluopyram + prothioconazole; the combination of benzovindiflupyr + prothioconazole gave an inferior performance at some sites. Fenpicoxamid performed in line with the most effective co-formulations. This investigation shows a clear link between reduced field efficacy by solo SDHIs as a result of increasing problems with sensitivity shifting and the selection of several SDH-C mutations. The presented data stress the need to practice anti-resistance strategies to delay further erosion of fungicide efficacy.

S u m m a r yIn the years 2001 and 2002 at the Institute of Plant Protection Branch in Sooenicowice research work was performed on seed treatment with fungicides against leaf diseases of spring wheat cv. Ismena caused by pathogenic fungi: Blumeria graminis, Phaeasphaeria nodorum, Puccinia recondita i Pyrenophora tritici-repentis. Two variants of protection were included in the experiment: seed dressing with fungicides or seed dressing and single application of foliar spray at GS 49.At early growth stages of spring wheat a very high biological activity against powdery mildew, septoria leaf spot, brown rust and tan spot was recorded for seed dressing containing triticonazole+prochloraz. In the case of triadimenol+imazalil+fu-beridazole only a weak, but long-lasting effect against brown rust and septoria leaf spot was observed. Leaf infection as well as 1000 grain mass and yield, in the experimental combination with using triticonazole+prochloraz were on the same level as in the experimental variant where after seed dressing with triadimenol+imazalil+fuberi-dazole plots were sprayed with tridemorf+epoxykonazole at GS 49. It was concluded that seed dressing preparation containing triticonazole+prochloraz constituted a good base for protection of spring wheat against foliar diseases.