Syngenta has defended the performance of its combination triazole fungicide, Cherokee, after the publication of Pesticide Safety Directorate trials results suggested the activity of the individual components against Septoria tritici in wheat was relatively poor.

Wheat growers concerned by the results needed to look at the effectiveness of the whole product, the firm’s David Ranner said.

“In over 20 small plot trials and widespread commercial use last season Cherokee frequently matched more expensive products for both Septoria tritici control – where it has consistently given in excess of 90% control – and good yield delivery.”

Individually propiconazole and cyproconazole only gave 30% control of Septoria tritici in an eradicant situation across the three PSD trials.

But applying mixtures of triazoles with complementary disease strengths and movement properties, as in Cherokee (propiconazole + cyproconazole + chlorothalonil), had regularly improved performance, Mr Ranner explained.

The addition of chlorothalonil was also extremely important to performance.

Shifts in Septoria tritici sensitivity to triazoles had occurred, he admitted, but it underlined the importance of adding Bravo (chlorothalonil) to triazoles to protect their future effectiveness and to boost performance.

“Ultimately farmers have to decide which fungicide to use based on value for money in terms of disease control and output, not just on what it contains.”