There has been a clear reduction in the field performance of all azole fungicides since the mid 90s. The graph below shows the variability in performance of epoxiconazole against Septoria tritici since the mid 90s. Each point represents the level of control achieved by a single application of a half-dose of Opus in a fully-replicated HGCA Appropriate Dose experiment.
Although there appears to be a general trend down in terms of activity (line A), there is increasing evidence that in the last 3-4 years the decline in activity may have stabilised at current levels of performance (line B). This would be good news as effective control of septoria can still currently be achieved with the better azole fungicides (epoxiconazole and prothioconazole) despite the decline in activity. However, the field performance of older azoles appears to have been affected to a greater degree.
When the same data are examined at full and quarter-dose (see the graph below) it is clear that with lower doses there is much more variability in performance.
Azoles are the basis of all wheat fungicide programmes so are key to effective disease control, both now and in the future. Key questions are:
•Is further erosion of azole fungicide efficacy likely?
•What are implications for Septoria control in the future?
•Can we safeguard current and future chemistry through effective resistance management?
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