Following the detection of resistance to strobilurin fungicides in Septoria tritici in 2002, farmers and advisers increasingly rely on azole fungicides as the foundation for all wheat fungicide programmes. Lab studies have shown changes in the sensitivity of Septoria tritici to azole fungicides and HGCA-funded experiments over the past 10 years have shown a gradual erosion of field performance of azoles against septoria. HGCA experiments in 2006 compared the activity of the main azoles currently marketed in the UK for the control of S. tritici to see if their activity has been compromised by shifts in sensitivity of the septoria population.
The pictures below are from the ADAS Rosemaund experiment in Herefordshire in 2006 showing the appearance of experimental plots on 20th June, 35 days after treatment. These photographs are from plots treated with a single spray at double the label recommended dose.
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| cyproconazole |
epoxiconazole |
fluquinconazole |
flusilazole |
flutriafol |
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| metconazole |
prochloraz |
propiconazole |
prothioconazole |
tebuconazole |
The disease assessment done at the same time is shown below. This shows the level of septoria present on the flag leaves.
It is clear from these experiments that the performance of some of the azole fungicides has been affected by changes in the sensitivity of the septoria population to the point where some give poor control of the disease when used alone in high disease pressure situations. (The HGCA experiments are carried out on very susceptible varieties under high disease pressure in order to expose any potential weakness in products). Many of these fungicides are still active against other diseases such as the rusts and can be used in mixtures to broaden the disease control spectrum. Many are sold in mixture with other azoles and chlorothalonil to improve control of septoria. However, it is clear that many azoles, if used alone under high disease pressure, would not give adequate control of septoria. | 
