FARMERS in Scotland are expected to have a low level yellow rust incidence this spring and summer, but are being told to watch out for Blue 7 and Red 24 big hitting races

The cold winter has meant that yellow rust incidence is currently low, but with some known ‘big-hitting’ races and only three Recommended List (RL) varieties resistant to early ingress of the disease, agronomists are recommending vigilance.

Dr Sarah Holdgate, of NIAB, who manages the UK Cereal Pathogen Virulence Survey (UKCPVS), said: “There is not a lot to report at the moment. The frost and snow we have had is helping to slow yellow rust down a bit.”

Most winter wheat varieties are susceptible at the seedling stage to at least one race of yellow rust. She added: “Only three varieties on the winter wheat Recommended List are resistant at this time of year and those are Costello, KWS Crispin and KWS Siskin and I have not heard anything unusual about any of those.”

During the high disease pressure year 2016 there were some big changes in yellow rust populations and she added: “A couple of varieties went down by two points or more on the Recommended List that year, so we had suspicions that there was at least one new race on the go.

“What we saw in 2017 was that, actually, things didn’t really change a lot. So what had changed in 2016 remained – however, there were no new changes so we suspect that we are stable for the moment, but never say never. Blue 7 and Red 24 are the current big hitters in terms of yellow rust races which are doing the most damage.”

Scott Milne, the agronomy manager for Scotland at BASF, told The SF: “At the moment, I am not particularly concerned about yellow rust in Scotland but it is something I always advise growers in the Borders, Lothians and Fife to keep an eye out for. These are often the areas that it shows first.”

And infection occurs mainly in coastal areas, but Mr Milne added: “We have seen it moving up the country in the last couple of years. KWS Barrel is being widely grown this year and has a good rating for yellow rust resistance, with an 8. However, a lot of Zulu is in the ground, which is a 5 for yellow rust, so in coastal areas I would definitely regard it as susceptible.

"The great thing for us is there is absolutely no slippage in the control of yellow rust with the active ingredients that we have available. That’s regardless of whether it’s triazoles, SDHI’s or strobilurins – they are all still doing a good job.”

If yellow rust is present at T0, he recommended knocking it out with an azole. “Any of our epoxiconazole-based products will do a good job and then make sure spray intervals are kept to approximately three to four weeks,” he said.

“At T1, Adexar is a good option because it is proven to be the best fungicide on yellow rust and septoria and then at T2 follow up with Adexar, or Librax. I would always recommend two SDHIs as we have to go for yield and two SDHIs are the way to do that.

"To ensure the best anti-resistance strategy, our philosophy is always to mix a good SDHI, a good triazole and chlorothalonil, or another multi-site, use robust rates and keep the spray intervals correct,” he said.