The effectiveness of all triazole fungicide active ingredients with a label claim for Septoria tritici control in wheat will be tested this spring in four trials specifically commissioned by the Pesticides Safety Directorate.

The trials are in response to PSD being made aware of recent data, particularly in the HGCA appropriate fungicide dose trials, suggesting some triazoles may no longer be able to achieve consistently the 80% control of septoria required to make a label claim of control.

Four trials, three in England, one in Scotland, will be used to test the triazoles, but in contrast to the HGCA AFD trials which are one-spray only, each active substance will be applied at full label rate twice.

ADAS plant pathologist Bill Clark believes PSD is acting responsibly in commissioning the trials.

“Part of PSD’s role is to review label claims, particularly with regard to resistance issues.

Responsible

“Historically it has made manufacturers put something on the label to the effect where resistance occurs efficacy may be reduced, but this is not really that helpful to growers.

So one could argue it is taking a more responsible view.”

The trials are likely to ask questions of the older triazoles, Mr Clark suggests.

“But I expect epoxiconazole and prothioconazole will work perfectly well.”

Under more pressure could be Bayer CropScience’s Folicur (tebuconazole), which the AFD trials suggests has drifted in performance in recent years.

But Bayer product manager Peter Stacey welcomes the chance for the product to clear its name.

“The AFD trials are not normal practice; they are an extreme test under severe pressure.

These trials are testing the product as it would be used in a more normal manner.

I’m not expecting there to be any problems.”

PSD intends to test a representative product for each triazole active substance approved for use against septoria.

If the field performance of any is found to be seriously reduced it intends to take action to make growers aware of the decline in performance and, potentially, make label changes.

Manufacturers will have the chance to submit their own data if they feel PSD’s proposals are unjustified.

mike.abram@rbi.co.uk