Key points
This trial was established to investigate if alternating or mixing triazole fungicides increases their efficacy against Septoria tritici blotch (STB) compared with sequential application of one triazole and to examine the influence of the treatments on the sensitivity of the pathogen to fungicide.
The work compares triazoles applied on their own. This is not suggested as commercial practice.
Four sequential applications of a full rate of Proline yielded significantly more than Opus® or Sportak® EW applied at full rates at the same timings.
In four spray programmes, mixing half label rates of Opus and Proline® or alternating full label rates of Opus followed by Proline achieved similar yield and levels of disease control to full label rates of Proline applied alone.
In a four spray programme, full label rate mixtures of Opus plus Proline achieved a significantly higher yield than equivalent programmes based on a full label rate of Proline alone, although disease control was similar.
The addition of two applications of the SDHI fluxapyroxad (in Adexar®) as part of a four spray programme achieved similar yields and levels of disease control to sequential full label rate applications of Proline.
The highest margin over fungicide cost (MOFC) was $1191/ha for alternating four full rates of Opus and Proline. The MOFC for mixing four half rates and four full rates of Opus + Proline were $1173 and $1142/ha respectively.
Plant & Food Research will be analysing the sensitivity of the STB pathogen in samples taken at the start and conclusion of this trial.