Trials confirming that strains of the potentially devastating wheat disease, septoria tritici – which is highly resistant to key fungicides – were circulating in the UK are “toward the worst end of expectations”, according to researchers.
And terming this a “warning shot”, plant health experts yesterday said it was imperative that the whole industry adopted strategies to ensure the continued efficacy of fungicides used to control one of the most challenging diseases for grain growers.
Work for the Agricultural and Horticultural Development Board (AHDB) showed that some samples of the disease from crops in 2015 were highly resistant to the key fungicide, Succinate Dehydrogenase Inhibitors (SDHIs).
The results came from tests on susceptible seedlings in a glasshouse using field rates of straight SDHI fungicides – and while higher rates than were used commercially offered some control of most strains, some were resistant even to full rates.
“This confirms, more than ever, that it is critical to adopt best resistance management practices to slow the spread of these strains and maximise the effective lifespan of the SDHIs,” said Dr Paul Gosling, who manages resistance research at AHDB.
Edinburgh-based plant pathologist Professor Fiona Burnett, who chairs the Fungicide Resistance Action Group (FRAG-UK) added: “It is imperative that the whole industry acts together to actively manage this situation.
“We’ve updated the FRAG-UK guidelines, which emphasise the need to use SDHIs with robust azole doses and the use of multisites in programmes.
“Azoles provide the win-win for 2016, both in terms of helping to protect the SDHIs but also in widening the efficacy against yellow rust this season.”
Although the research had shown that the frequency of the highly resistant isolates was extremely low in the UK in 2015 – and that good control of septoria from SDHIs was still anticipated in 2016 – Burnett added that the ability of these new highly resistant mutated strains to survive and increase was a cause for concern.
“Growers and agronomists will continue to need to take resistance management seriously and actively manage the risk in crops,” she said.