A crop used in beer and whisky production, soups and as animal fodder is affected by a disease found in wild grass, according to leading agricultural researchers from St Albans and Harpenden.

Farmers and researchers have puzzled over the source of a disease called leaf blotch, caused by a fungal pathogen, hitting the leaves, ears and stems of barley.

It decreases grain quality and reduces crop yields by up to 40 per cent.

But St Albans’ Bruce Fitt, professor of plant pathology at the University of Herts, said research had shown that the fungal pathogen causing barley leaf blotch could be found on wild ryegrasses.

Such grasses are common as weeds within cereal crop fields, and grow along surrounding field margins.

Barley is the second most important cereal crop grown in the UK, used as animal fodder, in human foods such as health foods, soups and stews, and also in the drinks production industry.

High quality malting barley underpins beer and whisky production and is worth around £20 billion to the UK economy.

In a study, both DNA and plant testing showed that the leaf blotch pathogen which affects barley can be found on wild grasses and was virulent on commonly grown varieties of barley.

Prof Fitt said: “Crops that appear to be clear of disease can suddenly develop leaf blotch symptoms unexpectedly.

“If this pathogen species can be spread from wild grasses onto barley crops and back again, further investigation is needed to identify how widespread this species is and also the role that wild grasses play as sources of disease for other crops such as wheat.”

The fungal pathogen has been studied in a project funded by the Perry Foundation.

Findings have been published in a paper co-authored by Kevin King and Jon West, both from Rothamsted Research in Harpenden, Patrick Brunner, of ETH Zürich University, Paul Dyer of the University of Nottingham and Prof Fitt.