Farmers should look up the Recommend List (RL) disease ratings of their varieties, monitor crops and use AHDB fungicide efficacy data to manage the disease, according to AHDB senior crop production scientist Mark Bollebakker.

He said: “Most varieties on the RL only show a moderate level of resistance to brown rust and a few are quite susceptible.

“The early infection and susceptibility of varieties means we need to prepare for an outbreak, should conditions remain conducive to the disease.”

Disease check

Brown rust severity varies seasonally and geographically, with outbreaks typically occurring when temperatures climb above 15˚C to 25˚C, primarily in southern and eastern UK. This year, disease pressure may be higher than average across much of the UK.

According to SAC, growers in Scotland should not ignore the disease, as it can be an issue in warm, humid weather.

Once established, the disease can cycle very rapidly in favourable conditions, with symptoms appearing only five to six days after infection.

The disease typically peaks in mid-summer, however this year, low levels of infection were recorded as early as March at RL trial sites due to a mild winter.

Brown rust symptoms

Farmers should look for small pustules on the leaf surface, which are less than 1mm in diameter. Brown rust pustules do not develop in lines along the leaf.

Rust-active fungicides

AHDB head of Farming Systems and Agronomy Ollie Johnson said: “This season, farmers should consider increasing their use of rust-active fungicides at the T2 timing to counter the threat, especially on relatively susceptible varieties. T2 is the most economically important spray, so a lot rests on it.

Head of farming systems and agronomy at AHDB, Ollie Johnson said: “Farmers should consider increasing their use of rust-active fungicides at the T2 timing to counter the threat, especially on susceptible varieties. T2 is the most economically important spray.

“AHDB fungicide performance work details the relative performance of key fungicides against brown rust and other foliar pathogens of cereals.

“The results can help farmers target brown rust, as well as the other main diseases at this timing, such as septoria tritici and yellow rust.”

The trials, which use high-risk locations, highly susceptible varieties, and one spray timing (T2 for brown rust trials), provide a tough test for fungicides.

Products containing isoflucypram or mefentrifluconazole have been highly effective against brown rust, with useful activity from pydiflumetofen.The pathogen causing brown rust in wheat (Puccinia triticina) is specific to wheat and will not infect other cereals like barley, rye and triticale. Different related pathogens cause brown rust in other cereals.

Fungicide performance curves for brown rust, can be viewed at ahdb.org.uk/fungicide-performance