The sensitivity of septoria to SDHIs and azoles is eight and 14 times lower, respectively, than what it was in 2005. This was reported by Steven Kildea at the Teagasc National Tillage Conference last week.
It’s not a localised, specific effect, he said, and resistance has been detected from the north-east to the south-west of the country.
Kildea stated that a number of azoles may go off the market as products are reviewed. Others may have restricted usage. However, he added that new actives are coming down the line.
Image source: Teagasc
Diversity is key
Kildea explained that, while resistance to products has been found, good control of septoria can still be achieved. Differences still exist between azoles and use should alternate between the two groups.
Teagasc research has also shown that the more active ingredients in the tank, the better the yield. For example, one Teagasc trial showed that yield increased where Elatus Era was applied compared to Elatus alone. Similarly, yield increased where Elatus Era and Bravo were applied compared to Elatus Era on its own.
Image source: Teagasc
SDHIs
Resistance to SDHIs is widespread across the country and there is no differentiation between SDHIs. In addition, high levels of resistance have been found in all regions.
Broad-spectrum fungicides
Kildea described chlorothalonil as having effective control. He stated that it gives good protection and good control in general. It is most effective when added to a mix, but may also help to protect leaf two between main spray timings.
Recommendations for 2018
Kildea outlined the Teagasc winter wheat disease control recommendations for 2018. Where disease pressure is high early in the season, a multisite or a stobilurin may be applied. An azole mix and a multisite should be applied at T1. Where disease pressure is high, an SDHI should also be added.
T2 applications should include an SDHI, azole and a multisite. T3 should include an azole mix and possibly a multisite.
Data source: Teagasc