HGCA tested the main azole fungicides available for wheat in two dose-response experiments in 2006. These results match very closely the results from PSD-funded experiments which tested all currently available azoles against S.tritici in 2-spray programmes at full label doses. The PSD results were presented at the AAB Conference in November 2006 and at HGCA Workshops in 2007. A cross-site summary of the PSD experiments is shown below. Results showed that:
•There was a very wide range of activity of current azoles against S. tritici.
•Under very high disease pressure many are not sufficiently active to give adequate control of Septoria if used alone.
•Epoxiconazole and prothioconazole were clearly highly active, even when used alone.
The graph above, showing the percentage control achieved from each treatment (all at full label dose, applied at GS32 and again at GS39) clearly shows the wide range of activity, with poorer products only giving 30-40% control. This level of activity is not consistent with a label claim for control of septoria.
The HGCA experiments allowed a direct comparison between the HGCA Appropriate Fungicide Dose experiments (where single sprays are applied) and the PSD experiments where 2-spray programmes at full label dose were used. The graph below shows the relative performance of the double dose treatment from the HGCA experiments.
The full dose response curves generated from the 2006 experiments are shown below. These are shown compared with the 1994-2004 data set. It is clear that the performance of many azoles in 2006 was considerably poorer than the performance derived from data from the 1994-2004 experiments. This is largely due to the fact that the curves for older products generated in 2004 are biased towards data from the mid to late-90s when all azoles were more effective against S. tritici . The 2006 data confirm the position of epoxiconazole and prothioconazole as the most effective azoles against S. tritici with fluquinconazole and metconazole next in order of efficacy – very similar to the order of efficacy from the PSD experiments.
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