An oilseed rape leaf showing symptoms of light leaf spot© Bayer

Oilseed rape growers in northern Britain face a higher risk from the crop’s most yield-damaging disease light leaf spot than those further south.

The risk of the disease is expected to be worst in northern England and the Moray Firth area of northern Scotland this season, according to a disease forecast.

This light leaf spot survey assesses the proportion of oilseed rape which will have more than 25% of plants affected in the spring, based on the previous incidence of the disease and the weather.

The risk ranges from 66% in northern England and the Moray Firth, down to 13% in East Anglia.

See also: Wet autumn could herald oilseed rape disease concerns

Moderate risk

Neal Evans, plant pathologist at independent forecaster Weather Innovations who puts together the forecast, said the overall risk this season was “moderate” but there are some regional hotspots.

He added the long dry spring had limited disease transfer from leaves to the pods.

“Last season was fairly strange, with a large light leaf spot epidemic seen in most crops during the winter but the long, dry spring limited transfer to pods,” he said.

Dr Evans suggested the forecast should only be used as a guide and crops should be inspected regularly on a field-by-field basis, and growers should look to apply a suitable fungicide as soon as the disease is detected.

The risk varies from 52-56% in the rest of Scotland, 45% in Lincolnshire, 58% in Wales and the West Midlands, and ranges for 30% to 40% across southern England.

A PDF of the light leaf spot forecast trends for 2013-17 can be downloaded from the AHDB’s website