Teagasc research has confirmed that Irish septoria strains are able to overcome a source of genetic resistance in some of the wheat varieties currently on trial for the seed market.
A report from the variety trials open days in June outlined that varieties with Cougar in their parentage appeared poor on septoria resistance.
Dr Steven Kildea of Teagasc outlined that: "Cougar derived resistance has been included in commercial breeding programmes for a number of reasons, including its initial resistance to septoria.
"However, our work has now confirmed that this source of resistance is vulnerable to Irish strains of septoria. With upwards of 20% of the Irish winter wheat seed available for autumn 2021 expected to be made up of varieties bred from Cougar the implications of these findings are immediate."
Four of the six varieties up for recommendation for the Department of Agriculture's winter wheat 2021 recommended list were bred from Cougar.
Rapid glasshouse work was carried out to investigate the breakdown of these crops to septoria.
While it has been shown that these strains can cause high levels of septoria in varieties bred from Cougar there is no evidence to suggest that these strains are "more aggressive" on other wheat varieties.
Research is ongoing to see how these strains have spread in septoria populations here in Ireland.
On a positive note, Kildea outlined that "following intensive sensitivity analysis these septoria strains are similar in fungicide sensitivity to the wider Irish Z tritici population".
Teagasc has reemphasised the need for farmers to practice integrated pest management (IPM) strategies and to be aware of the risks associated with varieties they choose and to consider the septoria pressure in the locations where the crop is being grown.
Teagasc has suggested keeping these varieties to a minimum (the four varieties currently take up 20% of the seed availability for 2021), delaying sowing where possible, matching disease risk to fungicide choices and ensuring the correct application timings for septoria control.