New Yellow Rust Strain Confirmed

Yellow rust has been present in many Scottish wheat crops from very early this season. It was unexpectedly common on varieties like KWS Dawsum and Bairstow which had, until now, shown good juvenile plant resistance to the disease. Last week Niab confirmed the fears that a new variant strain of yellow rust has been found. Their annual survey of yellow rust is run as part of the UK Cereal Pathogen Virulence Survey.

The research shows that the new strain detected can infect varieties of wheat which carry the ‘all stage resistance’ or ASR gene (Yr15) which is present in most, if not all, of the UK varieties that show juvenile resistance. The new strain also goes on to sporulate well.

This gene was present in a huge proportion of wheat in the 2024 harvest and in almost 60% of the wheat in the ground now, so the selection pressure for yellow rust to find a way to overcome it has been huge. There is some hope that the affected varieties, which succumbed early because that gene had failed, may have other more diverse adult plant resistance genes waiting to kick in. Late season assessments at the variety trial sites will help to see if that’s the case. It will be useful to look at how the varieties have stood up at the upcoming crop trial open days.

Earlier infections of yellow rust seem to have been managed reasonably well through foliar sprays, but the burned-out stripes of previous infections are scarring the leaves of many previously infected crops. Most head spray (T3) fungicide options are built around azole fungicides which are strong against yellow rust, but do walk crops carefully and adjust doses and product choices if your crop is infected. Always check maximum application numbers and last application timings carefully for this final spray timing.