It is now apparent that significant changes are taking place within the UK’s population of yellow rust fungi.
Recent reports from Agricultural and Horticultural Development Board (AHDB) recommended list (RL) trial sites in the northeast of England point to enhanced yellow rust activity in young plants across a range of winter wheat varieties.
There are also the first hints of something unusual starting to happen in other RL trial regions.
As the yellow rust pathogen population is highly diverse, it is not unusual to detect new strains.
However, these early observations suggest that there may be a significant new strain or strains in the UK pathogen population that have been not seen before.
Interestingly, some varieties historically classified as susceptible at the young plant stage are currently relatively clean at the impacted trial sites.
This suggests a potential pathogen population shift that may have displaced some other yellow rust strains.
Mark Bollebakker, who manages the RL trials at AHDB, said: “The trials in question were at about growth stage 30 at the time of inspection, so adult plant resistance had not kicked in.
“When it does, from stem extension onwards, these varieties may outgrow initial infection. However, it is difficult to predict what will happen.
“We have sent sample for testing to give us a better understanding of what we are seeing.”
AHDB is now committed to field trials with the sole purpose of gathering data on young plant resistance to the fungi at sites traditionally associated with high yellow rust pressures.
This will allow disease assessments to be made at the young plant stage when infection pressures are naturally high.
To boost pressure further, the trials are also artificially inoculated with yellow rust (multiple isolates) with a highly susceptible variety grown (between the plots) to spread the disease.
Varieties that are impacted by yellow rust at the young plant stage are more likely to require treatment with fungicides that have good rust activity during the T0–T2 fungicide period, even if they have a high adult plant disease resistance rating.
Significantly, yellow rust has already been identified in 2025 winter wheat crops growing in Co. Louth.
These developments add to the early identification of brown rust in winter wheat RL plots across regions of England in 2024: it is normally regarded as a late season disease of wheat.
