Reduced yellow rust resistance among winter wheat varieties means growers should look at additional ways of managing the disease this autumn.
A substantial number of winter wheat varieties have seen a fall in their single-year yellow rust resistance ratings compared with previous ratings which were based on three years of data.
The drop follows the yellow rust pathogen overcoming the YR15 plant resistance gene, with some variety resistance ratings tumbling by as much as 4 or 5 points on the 1-9 resistance scale this autumn.
Delayed
“This puts extra reliance on other methods to help counter the disease – not least in case fungicide applications next spring end up being delayed,” says Mike Thornton of agronomy firm Procam.
Yellow rust can flare up rapidly in suitable weather. And with little movement towards drilling wheat varieties with greater resistance this autumn, growers should be thinking of ways to help make plants more resilient.
“Yellow rust tends to be less of a problem in earlier-drilled winter wheat crops than in later-drilled ones. So avoiding later drilling is a consideration – but this needs balancing against the increased risks from Septoria and grassweeds from early drilling.
“But in addition to drilling date, we also know that plants under stress tend to be more susceptible to yellow rust infection, and there are several ways to help plants become less exposed to stress factors.”
Correct nutrition
Beginning in autumn, these include getting autumn nutrition right to improve rooting for better access to soil moisture and nutrients. Arguably, this is something that growers should be considering anyway, in case next year is also incredibly dry.
Potash (K) and phosphate (P) are both important for root development. Mr Thornton recommends using soil testing to assess the levels of these nutrients in the soil. Growers should also to assess the levels available to the plant, he says.
Low soil temperatures as we head towards winter tend to reduce phosphate availability and acidic soils cause phosphate to be locked up, says Mr Thornton.
Pre-emergence
If there’s a need to improve phosphate availability, consider a pre-emergence application of LibPhos. This preferentially binds to calcium in the soil, freeing up soluble phosphate that can be absorbed by the plant.
“To encourage rooting at the post-emergence stage, consider a seaweed-based biostimulant such as Zodiac, or the pidolic acid and phosphite biostimulant, Incite. These types of treatment are a sensible cost and can soon deliver a return.
“They can be tank-mixed with certain aphicides. If you’re paying to go through the crop with the sprayer anyway, it makes sense to get the best return on investment from that operation.
“We need to think about adopting an intentional approach to building better root systems in autumn. Even if your farm didn’t succumb to the effects of reduced wheat yellow rust resistance in 2025, it’s still important not to be complacent.”