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Teagasc Scientists Find Shift in Septoria Sensitivity to Triazoles

17 April 2009 Teagasc

New research at Teagasc Crops Research Centre, Oak Park, Carlow has found that current strategies to control the wheat disease Septoria tritici may be under threat. In recent weeks strains of Septoria tritici were found in some crops that were less sensitive to the fungicide prothioconazole (Proline) in the laboratory than any previously tested. These strains also show a reduction in sensitivity to epoxiconazole (Opus).

Dr Eugene O’ Sullivan, plant pathologist at Teagasc Crops Research Centre, Oak Park said: “It is not clear if these changes will affect fungicide performance in the field this year but fungicides should be used in a way that will reduce selection pressure. Triazole fungicides should not be used in T0 (pre-T1) sprays. In subsequent sprays, prothioconazole and epoxiconazole should only be used in pre-formulated mixtures or tank mixes with partner fungicides with different modes of action.”

The triazole group of fungicides have been the mainstay of cereal disease control for three decades. The strobilurins, popular in the late 1990s and early 2000s quickly succumbed to developing resistance in 2003. Growers have relied on triazole fungicides for most of their disease control since then. “We need to do all that we can to avoid any reduction in the efficacy of triazole fungicides,” stated Dr O’ Sullivan.

This development is a cause for major concern according to Professor Jimmy Burke, head of Teagasc’s Crops Research Centre. He said: “It is not clear how the shift in insensitivity will affect disease control by prothioconazole in the coming growing season. Intensive monitoring of the evolving fungicide sensitivity situation will continue at Oak Park. Teagasc researchers will monitor developments in the field as the season progresses, testing the efficacy of the fungicide in crops. In the meantime, growers must choose fungicide strategies wisely.”

Previous studies by scientists at Oak Park have shown a reduction in sensitivity of septoria to the triazole fungicides Folicur and Caramba but not to Opus and Proline. But this has now changed and growers are warned to be vigilant so that world class yields can still be attained,” said Professor Burke.

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