The Fungicide Resistance Action Group-UK (FRAG-UK) is urging growers and agronomists to adhere to guidelines on resistance management so that declines in sensitivity to either triazole or SDHI fungicides are not accelerated through high-risk practices.
In a statement issued in response to reports of laboratory and field isolates of septoria tritici with reduced sensitivities to SDHI fungicides, the group recommends several measures to reduce the risk of fungicide resistance development and extend product life.
There have been several examples of laboratory mutants of cereal pathogens, including septoria and net blotch, showing reduced sensitivity to SDHIs. In November 2015, Rothamsted Research reported low frequencies of septoria isolates with reduced SDHI sensitivity in UK field populations, while earlier this month Teagasc in the Republic of Ireland confirmed the detection of field isolates of septoria with reduced sensitivity to SDHIs.
Some of these isolates had a mutation in the SDHI target site which had not previously been detected in field isolates, says FRAG-UK.
Follow the statutory requirement to limit the number of applications to two SDHI fungicide-containing sprays
Always use SDHI fungicides in mixture with a fungicide from an alternative mode of action group, which has comparable efficacy against the target pathogen(s)
Tank mixing SDHIs is not an anti-resistance strategy. In any tank mix the SDHI should be applied in a balanced mixture with at least one fungicide with comparable efficacy against the target pathogens from an alternative mode of action group
Field performance from SDHIs is still anticipated to be good in 2016, says the group. However, strong stewardship is needed to prevent a rapid increase in the frequency of isolates with reduced sensitivity to SDHIs in the septoria population.
Dr Paul Gosling, AHDB research manager, says: “AHDB supports the resistance action groups in their effort to provide evidence-based, independent and practical information on resistance management. FRAG-UK’s statement follows the release of our latest fungicide performance data. Our trials show that SDHIs remain the most active chemistry against septoria when applied in protectant situations.
“However, the new information on SDHI sensitivity, once again, shows why it is critical to adopt best resistance management practices.”
The full FRAG-UK statement is available here
View ADAS pathologist Jonathan Blakes’s presentation to the AHDB Agronomists' Conference on using fungicides effectively in wheat, barley and oilseed rape