1 October 1999

Fungal disease in barley may lie undetected

By Andrew Swallow

OMPHALINA patch, a soil- borne fungal disease, has severely cut barley yields for one Worcs grower this season. It could well be going undiagnosed elsewhere, say experts.

"Winter barley was very disappointing," says Steven Watkins of Sheepcote Farm, Upton-on-Severn. "It yielded only 2t/acre where normally we get over 3t."

It was first noticed that the crop was under-performing in April.

"As the crop grew away, discrete areas started to look awful," says Technicrop agronomist Paul Tainty. "Imagine the worst lime deficiency symptoms – the plants were pale yellow and just did not want to grow. It looked a bit like chronic manganese deficiency, but without the floppy leaves."

Full tissue and soil analysis from affected patches revealed nothing to cause the visual symptoms. "The only thing a bit low was sulphur," he says.

Then, in a technical handout, Mr Tainty stumbled across a description of omphalina. "We pulled up some plants and washed the roots, and that was it."

Each root bundle contained four or five cotton wool-like balls of fungus, each about the size of an oilseed rape seed.

That is typical for the disease, though above-ground symptoms are often limited to stunting, says ADAS Wolverhampton pathologist John Scrace. "Plants are normally green, but stunted."

Yield loss in affected patches ranges from 25 to 50%. Light land favours the disease and barley is most commonly hit, though wheat and rye can also be infected. Scler-otia survive in the soil long enough to span most rotations, he says.

"Well never grow barley in the field again," echoes Mr Watkins. &#42

OMPHALINAPATCH

&#8226 Soil-borne fungal disease.

&#8226 Cereals, mainly barley, hit.

&#8226 25-50% yield losses.

&#8226 Distinct stunted patches.

&#8226 Cotton-wool beads on roots.

&#8226 Rotation no cure.