Wheat disease control, the Irish view
In the third of BASF’s Funginar series, this one giving an update on disease control in winter wheat, John Spink Head of Crops, Environment and Land Use Programme, at Teagasc, spoke of ways of tackling the challenge of high disease pressure in the damp Irish climate.
“Wheat growing in Ireland is limited to the south and east of the country where on average there is 800-1500mm of rain, evenly distributed throughout the year, meaning no drought conditions. Yields are high with a national average of 10 t/ha; however, most people aim for 12.5 t/ha in first wheats. The damp climate means that there is high wet weather disease pressure, with Septoria and head blight the main diseases and Yellow rust making the occasional appearance.
Integrated Pest Management (IPM) for Septoria tritici blotch
The really difficult thing about IPM for Septoria in Ireland is that there is always enough inoculum around for an epidemic and what determines the amount of Septoria you are going to get is the weather in the 2-3 weeks after you have applied the fungicide. At present forecasts aren’t good enough to predict that weather accurately so growers need to monitor, assess the risks and modify their approach as they go.
Good disease resistant varieties are the first step of IPM. In Ireland, however, we have a smaller Recommended List than in the UK and anything with any sprouting or lodging problems doesn’t get included. So, some varieties that might be good for Septoria just don’t get on the list.
Single gene resistance is not sustainable. Virulence to Septoria resistance in the variety Cougar was detected in 2020, as well as strains also virulent to a range of Cougar based varieties. So, we need good varieties with durable resistance because major genes are overcome very rapidly.
It is key that resistant varieties are protected with fungicides and vice versa. We have to ensure it is a package approach to Septoria control, resistant variety plus fungicides, in order to ensure durable, lasting resistance.
Work done in collaborative trials at 21 sites across the UK and Ireland showed that sowing late increases the resistance rating of the variety, or conversely, sowing early reduces the resistance rating of the variety.
The concentration of ascospores declines as you go through the winter but there are enough ascospores around, even in November and December, to potentially cause late infection.
Matching fungicide programme to the disease risk
In its Septoria population, Ireland has over 70% of the mutation Cyp51-S524T, the prevalence of this mutation lessens as you go east into Europe, which is reflective of the lessening fungicide usage and disease pressure. This mutation really affected prothioconazole and epoxiconazole so the arrival of Revysol® and QII, InatreqTM are both welcomed. With the loss of chlorothalonil (CTL) we are really focussed on protecting these new actives by using folpet in our high disease pressure situations.
Focussing on leaf 3 and flag leaf sprays
We try to avoid using an azole early in the season, on leaf 4, as in-field selection can occur which then makes the Septoria harder to control later in the season. If there is no Yellow rust risk, then the advice is not to use a spray at T0 as there is not a yield response.
Our programme in terms of Septoria is really focussed on T1, the leaf 3 spray and the T2, flag leaf spray. We recommend folpet in the mix at both of these spray timings to try to reduce the risk of resistance to the main parts of the fungicide programme. Because of our disease pressure we would always use between 80 and 100% dose of all the chemistry.”
Use plant protection products safely. Always read the label and product information before use. For further product information including warning phrases and symbols refer to www.agricentre.basf.co.uk. Revysol® is the brand name for the active ingredient mefentrifluconazole. InatreqTM contains fenpicoxamid. Revysol® is a registered Trademark of BASF. All other brand names used on this publication are Trademarks of other manufacturers in which proprietary rights may exist © BASF 2021. All rights reserved.