International Symposium on Cereal Leaf Blights 2019 | University College Dublin, Ireland | 22-24 May 2019

Resistance to azole (DMI), SDHI and strobilurine class fungicides in field isolates of Zymoseptoria tritici in Baltic countries

Andres Mae*

Thies Marten Heick
Department of Agroecology, Aarhus University

Pille Soovali

Poster Presentation
Cultural Management, Fungicide Resistance and Epidemiology

Atrium, UCD O'Brien centre for Science
Poster 19

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In Estonia, outlined by the ECRI, the specific monitoring program ( for detection of leaf diseases on cereals is carried out since 2014 to undertake control measures when first symptoms detected to minimize the impact of disease. In Estonia the 2-spray strategy using 0.75 doseof fungicide is used to control Zymoseptoria in wheat.

In 2018 in addition to monitoring we also started fungicide resistance-related investigations. A total number of 63 isolates from Baltic countries including 29 from Estonia, 4 from Latvia and 30 samples from Lithuania were tested for sensitivity to epoxiconazole, prothioconazole-destio, tebuconazole and fluxapyroxade. This was the first year of testing and therefore there is no reference to previous years. In addition 10 samples from Finland were included into the study. Sensitivity testing was carried out as  bioassay analysing single spore isolates on different concentrations of fungicides.

The average EC50 value in Baltic countries (and Finland) to prothioconazole-desthio varied between 0.06–0.24 ppm, tebuconazole 1.25–17.7 ppm, and epoxiconazole 1.04–1.98 ppm. The samples were also analysed for CYP51 mutations. Frequencies of D134G, V136A/C, A379G, I381V, and S524T in the Finnish-Baltic region were lower than in other Nordic countries.

The average EC50 value for fluxapyroxade varied between 0.07–0.32 ppm. The isolates were analysed for SDHI mutations. SDHI mutations C-N86S, C-N86K, C-T79N, C-T79I, C-W80S, C-G90R, C-H152R were not found in the Finnish-Baltic region in 2018.

The frequency of mutation G143A conferring strobilurin resistance was high (50-70%) in all of samples from Estonia, Finland, Latvia and Lithuania.

Those findings demonstrate that although the presence of fungicide resistance mutations has been confirmed for azole and strobilurin class fungicide these mutations do not dominate (except G143)A in the Baltic region and there has been no reports in the failure of the field performance of these fungicides so far.