Recent research at Teagasc Oak Park showed the number of times a group of fungicides is used, and the use of effective mix partners, are the most critical practices to slow development of resistance.
Teagasc plant pathologist, Steven Kildea said: “Despite recent declines in the efficacy of azole fungicides, they are still an integral part of fungicide programmes for both disease control and as an anti-resistance partner.
"Therefore, for the coming season, SDHIs should only be used in mixture with a robust rate of azole and a multi-site fungicide, and should never be applied more than twice during the season.”
One strain of Zymoseptoria tritici found at a low frequency at Teagasc Oak Park, Carlow, at the end of the 2015 grain season, survived up to 100 times the concentration of SDHI fungicides compared to the most insensitive strains found in previous years.
A less insensitive strain was identified in the north east.
John Spink, Head of the Teagasc Crops Science Department, said: “Research is on-going to examine potential impact of these strains on disease control, and intensive nationwide monitoring is planned for early spring.”
Given the low frequency of these strains so far, good septoria tritici blotch control is still with SDHI fungicides in the coming season.
However, any increase in their frequency will threaten the future efficacy of this very valuable group of fungicides.