Reports of early wheat brown rust

In this blog, Senior Crop Protection Scientist Catherine Harries comments on reports of early wheat brown rust symptoms at commercial and Recommended Lists (RL) trial sites.

Last week, we wrote about observations of early yellow rust in UK wheat crops. Although wheat brown rust is generally considered a late-season disease, we have also received reports of early infection from this disease in commercial crops and RL trials.

In fact, in the RL fungicide untreated trial series, wheat brown rust has been seen at sites in Lincolnshire and Norfolk for a few weeks.

To put this in perspective, we did not record brown rust in RL winter wheat trials until 10 May in 2023. Last year, infection did not get going until mid-June, peaking in early July (see the figure, below).

Brown rust development appears to be several weeks ahead this year.

Brown rust percentage in RL trials (2023)

As with yellow rust, resistance to brown rust may be different at the young plant stage compared to the adult plant stage.

The expression of adult plant resistance (which the 1–9 disease resistance rating is based on) varies across winter wheat varieties.

Typically, it ranges from growth stage 20 to growth stage 49. However, cooler weather can delay it and high disease pressure can speed it up.

By growth stage 55, it is likely that all varieties will express adult stage resistance.

The UK Cereal Pathogen Virulence Survey (UKCPVS) tests which RL varieties are susceptible to brown rust at the young plant stage.

In recent tests (based on samples collected in 2023), all current RL (2024/25) varieties have been classed as susceptible at the young plant stage. One candidate variety (RGT Goldfinch) has been classified as resistant.

Unlike yellow rust, young plant stage resistance information for brown rust is not published in the RL tables.

So far, UKCPVS has already received several samples of brown rust (and yellow rust) from winter wheat crops in 2024 (shown in the figure below). 

Number of rust samples received by UKCPVS

Check the RL 1–9 disease resistance rating for your variety and take it into account in your fungicide programmes.

When it comes to rusts, be prepared to expect the unexpected. As pathogen populations change, varietal resistance can decrease (it can also increase).

Based on RL trial results, the wheat brown rust watch list reveals varieties that performed out of line with their RL disease resistance rating at some sites. It can help provide an early indication of changes to the pathogen population.

The latest brown rust watch list highlights KWS Zyatt (7), LG Astronomer (7) and KWS Extase (6) as varieties that had slightly higher levels of brown rust than expected (at 1–3 sites).

If you see unusual levels of brown (or yellow) rust in any variety (above what the ratings suggest), send a freepost sample to UKCPVS for testing. This will help us look for evidence of shifts in disease resistance and report findings to industry.