Wheat yellow rust watch list
Based on Recommended Lists (RL) trial results, the wheat yellow rust watch list can reveal varieties that performed out of line with their RL disease resistance rating at some sites. Use the list to help understand disease risk and focus in-season management.
Measuring disease resistance (key points)
- The UK yellow rust population is increasingly diverse, with large pathogen race variations across sites and seasons – and even individual leaves
- RL yellow rust disease resistance ratings use a simple scale – from 1 (least resistant) to 9 (most resistant)
- The ratings are based on a three-year data set and reflect average (across trials/years) disease levels/resistance on adult plants (after growth stage 55)
- However, these averages can mask relatively poor varietal performance at some trial sites
- The yellow rust watch list addresses this, as it indicates varieties that performed out of line with their RL disease rating in some trials
- Currently, the watch list broadly agrees with the RL disease ratings – most varieties widely perform as expected from their RL rating
- As the situation can change rapidly, it is important to monitor all varieties closely and report unusual disease levels to the UK Cereal Pathogen Virulence Survey (UKCPVS)
What is the watch list?
Introduced for the RL 2021/22, the wheat yellow rust watch list provides a way to flag unusual levels of yellow rust seen in some trials, compared with what the headline disease rating would otherwise suggest. This extra layer of information may provide a valuable early warning of a potential change in the UK’s race structure and help focus in-season management strategies.
Watch list category descriptions
The watch list orders varieties based on disease levels in the three worst trials for each variety (for the specified trial year), with three categories used to describe their performance.
Highly resistant varieties (near the top of the table)
The variety was resistant against the rust races present in all trials. The resistance is most likely to be effective against both common and uncommon races. A standard monitoring and fungicide programme is appropriate.
Medium-resistant varieties (near the middle of the table)
The variety was moderately susceptible to one or more races present in some trials. Refer to the RL rating to indicate whether this susceptibility is likely to be common (medium RL rating) or rare (higher RL rating). Monitor these varieties frequently. Be prepared to increase use of rust-active fungicides in the programme.
Low-resistant varieties (near the bottom of the table)
The variety was highly susceptible to one or more races present in some trials. Refer to the main RL rating to indicate whether this susceptibility is likely to be common (low RL rating) or rare (medium–high RL rating). Monitor these varieties frequently. Be prepared to increase use of rust-active fungicides in the programme.
Disease rating v watch list category
Close alignment between the RL disease resistance rating and the watch list category means a variety is most likely to perform as expected in all locations. The above chart is for illustrative purposes only. The coloured variety dots indicate the approximate relationship between the watch list and the RL disease ratings (RL 2021/22).
The yellow rust watch list (RL 2021/22)
Based on data from a single trial year (2019/20), the watch list also features the RL 2021/22 yellow rust disease ratings, for comparison. Currently, the watch list order broadly agrees with the disease ratings.
|Yellow rust |
watch list category
Winter wheat variety
|Highly resistant||KWS Siskin||9|
|Low resistance||KWS Zyatt||5*|
Varieties with an * indicate susceptibility to yellow rust before the T2 fungicide timing. Use the young-plant resistance status to indicate expected disease levels at this stage (before growth stage 55) and guide T0 and T1 fungicide treatment decisions. At this stage, most varieties are susceptible.
Due to the complexity of the yellow rust pathogen population, it is not possible to predict how varieties will perform during the growing season. Use the disease rating and watch list as a guide. However, if uncommon wheat yellow rust races arrive and/or spread (or established races diminish), varieties may not perform as expected. All RL varieties are on the watch list. Monitor all crops closely. Increase monitoring frequency following a mild, wet winter. Report unexpected disease observations to the UKCPVS.
Always consider all characteristics of a variety. Growing varieties with a range of yellow rust ratings, rather than only those with a very high potential resistance, may help to slow down resistance breakdown of some varieties.
While AHDB makes every effort to ensure data accuracy, it is impossible to eliminate all errors. Due to the restricted number of trials considered in the watch list, anomalous results will have a disproportionate effect on the yellow rust categorisations, compared with the effect on the main RL rating. For overall varietal risk, use the main RL rating.