WHEAT growers concerned by a reported decline in the activity of triazole fungicides against the disease Septoria tritici must look at the effectiveness of the whole product when using a triazole mixture, says a leading crop expert, and not just the isolated activity of its component parts.
According to David Ranner, technical manager for Syngenta, triazole dose rate has a big impact on final product performance, as does the addition of the fungicide Bravo.
Also, higher performance has regularly been seen from mixing different triazoles with complementary disease strengths and movement properties in the plant, he explains.
For growers, such a mixture can often be achieved more cost-effectively by using a pre-formulated product, rather than making a DIY tank mix of components, he adds.
"The specially formulated mixture Cherokee is a good example of this. It combines robust rates of two different triazoles, together with the anti-resistance partner of Bravo.
"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.
"Ultimately, farmers have to decide which fungicide to use based on value for money in terms of disease control and crop output," he points out, "not just on what it contains."
Recognising that there has been a shift in Septoria tritici sensitivity to triazoles, Mr Ranner says this only goes to underline the importance of adding Bravo to triazole mixtures – with its reliable activity against all strains of Septoria tritici – as a means of protecting their future effectiveness and boosting levels of performance.
"As well as its triazole and Bravo components, Cherokee also makes use of Weatherstik formulation technology," explains Mr Ranner. "This is the same technology that makes Bravo as a straight product stick so well to crop leaves, adding further confidence to the end result whatever the weather brings.''
