More winter frosts should mean any brown rust epidemic this season should not be as early or as severe as last season, although many of the risk factors for an epidemic do remain in place, fungicide experts suggested at an HGCA wheat disease workshop.

Last season, consistently higher temperatures contributed to the severe disease pressure, Jonathan Blake of ADAS explained. All through the season average monthly temperatures were higher than the 30-year mean.

That was particularly true of April, where they were around 3C higher, he said. It meant the latent period – how quickly the disease produces symptoms from infection – was only 10 days last year. “Usually it would be around 15 days in April, which meant there could be three cycles of infection in April rather than two. That might not sound like much, but rust reproduces exponentially, so it could mean that there were 10 times more spores than you would normally see.”

Higher temperatures also made the disease more efficient at infecting plants, he added.

Bill Barr of Prime Agriculture also pointed to the higher average temperatures as a key reason for the earlier outbreak. “April temperatures were comparable to May and June – so brown rust got going much earlier.”

Analysis over 20 years had showed that higher winter temperatures between November and January also had a direct correlation to brown rust in the following year, he said. Last season the temperatures in that period had also been 2-3C higher than usual.

This November was also milder than average across the UK, while January is also shaping up to be a mild, the Met Office says. December was only 0.1C above average.

But there had been more winter frosts this season, similar to the 30-year average, Mr Blake pointed out. “It is shaping up to be a more normal year. I’m not expecting a brown rust epidemic as early or severe this year, at this stage.”

Field observations suggest early season pressure is less too. “In the right fields you can see brown rust but we are finding it less than last year,” Mr Barr said.

But other factors, such as lots of susceptible varieties, the same virulent races and lots of disease carryover, meant it still could potentially by a high-risk season, he noted.