A fresh race of yellow rust has been detected in the UK for the first time and wheat growers are being advised to examine crops for abnormal amounts of the disease.
The new so-called Kranich race was identified from an isolate collected in 2014 and tested in the field in 2015, with some wheat varieties being slightly more susceptible.
The UK Cereal Pathogen Virulence Survey (UKCPVS) is currently monitoring the new race, but says the actual risk posed by it is unknown at this stage.
Sarah Holdgate, UKCPVS project manager based at crop consultants Niab, advises growers to monitor their wheat crops especially those varieties with high resistance to yellow rust and send samples to her at Niab if they are concerned.
“We are looking to make growers aware of the situation, but we don’t know the full scale of the effect of the new race,” she says.
Dr Holdgate reports that in 2015 trials, two new varieties wheat – Spyder and Graham – showed very slightly more susceptibility to the new strain, although they both have a high resistance rating of 8.
Yellow rust races and year first detected in the UK
The AHDB Recommended List ranks varieties on a 1-9 scale, with 9s showing high resistance with varieties such as Crusoe, Illustrious and Siskin down to Solstice and Kielder with a lowly rating of 3.
“Growers should be aware that the Recommended List ratings were based on last year and if this race takes off some of these ratings may not hold,” she says.
The Kranich race, named after a winter wheat variety, was first found in Denmark and Sweden in 2011, and is the first new race detected in the UK since 2011, the year which saw the Warrior race establish in the UK.
When the Warrior race arrived in the UK, some varieties such as Claire saw its resistance rating slightly reduced down to a 6.
Dr Holdgate says the Kranich race is believed to be an exotic incursion similar to the Warrior race, although the two are not closely related.
Recently, the European population of yellow rust has been replaced by new invasive strains, almost certainly originating in the Himalayan region and the Warrior group has come to dominate the UK population.
The AHDB says that if yellow rust symptoms are seen in crops, growers should strongly consider applying a T0 fungicide spray, irrespective of growth stage, to protect crops from further infection.