Conditions ripe for Septoria and yellow rust in Northern crops

The droplets of dew glistening in leaf axils are probably providing sufficient moisture to enable Septoria and yellow rust to keep cycling reflects Fiona Burnett as she strides out into the winter wheat plots at Bayer’s demonstration site in North Yorkshire for a closer look. 

With leaf 4 emerging or emerged in the 35 winter wheat varieties on the site at Stockbridge Technology Centre, Cawood, disease levels are relatively low after cold weather in January and February, followed by a dry March. 

Stooping to pluck a few leaves from a plot of KWS Zyatt, Fiona, who is professor of applied plant pathology at SRUC, and the Crop Doctor for the Cawood site, quickly identifies symptoms of Septoria. 

“There’s quite a bit of Septoria on the lower leaves, but it’s not excessive; it is what you would expect,” she says.  

A tebuconazole-based T0 fungicide is due to be applied to the plots on 3 April – the day after Fiona’s visit. While the decision to apply a T0 should be based on disease risk, not going in with a T0 could lead to a temptation to apply the T1 spray early and in doing so, compromise its efficacy, she says. 

“The difficulty at T1 is being able to properly hit leaf 3. It is generally a waiting game – nobody knowingly goes on with a fungicide at the wrong time,” says Fiona.  

With Septoria the main target at T1, yellow rust and possibly eyespot may also be in the mix.  

“I wouldn’t be worrying about brown rust at T1 this far north,” adds Fiona.  

And while a dry spell may be keeping a lid on disease, it is still important to have a T1 plan in place, she says. 

“I quite like the idea that people think about their fungicide programme, so that they've got a framework, they’ve factored in different actives and ideally, they are mixing and alternating those actives. 

“My ideal scenario would be an SDHI + azole, which keeps two actives in play, and I like to include a multisite, so I'd be putting folpet in the mix as well at the T1 timing. 

“Mixing an azole with an SDHI brings you a broader spectrum of activity and builds in a bit of resistance management too.” 

Fiona cautions against a reactive approach at T1, which could inadvertently compromise which actives are available for use at T2.  

“There is a lot of the season still ahead of us. The risk is that you leave a little chink in the armour that lets in yellow rust or brown rust, which you then have to manage before or at flag leaf. You want something that manages all your risks.” 

Pictured: Yellow Rust identified at Bayer’s demonstration site in North Yorkshire

Bayer technical manager Tom Sowerby, who is responsible for the Cawood site, is keen to hear Fiona’s view on what last autumn’s drilling pattern in the region means for fungicide programmes.  

He says: “In this area we had two distinct drilling dates: September, when everyone got on and got wheat in the ground and then we had a bit of wet weather, and we were into November.” 

Earlier drilled crops will certainly carry more disease risk, Fiona tells him. 

“Tailoring your inputs to that risk is key. The later drilled crops are maybe carrying a bit less disease at the moment but at this time of year the differences we see in disease levels are down to drilling date.” 

Pictured: Tom Sowerby and Fiona Burnett