Crop experts at Rothamsted Research Institute have issued a warning over heightened disease risk for light leaf spot and phoma in oilseed rape for the 2012/13 growing season.

They suggest that disease pressure will be high, as might be expected due to the dreary and wet summer endured throughout most of the UK. The warning was made on Tuesday (25th September) and coincided with areas of the UK receiving a month’s worth of rainfall in 24 hours.

Increased light leaf spot risk is predicted for many crops, as well as an early onset of phoma leaf spot outbreaks in most regions. The tortuous, extended harvest experienced by many growers has compounded the threat , resulting in many crops sown very late which are either yet to emerge or which consist of small vulnerable plants.

The cold, snowy winters and long wet springs of recent years have favoured light leaf spot, according to Weather Innovations plant pathologist Dr Neal Evans.

"It's become the 'forgotten disease' somewhat," Evans says. "The high incidence of the disease in crops of all regions last year means that there is a lot of inoculum about for the 2012-13 season and this is reflected in the forecast. There is a real need for extra vigilance this year."

The phoma leaf spot forecast prediction dates are generally 7-14 days earlier than last year across most of the arable growing region. An early onset of the epidemic combined with poorly developed crops could prove disastrous to an industry hit but what has generally regarded as a poor harvest.

Dr Peter Gladders of ADAS Boxworth says they have already seen leaf spotting on volunteer plants in western counties.

"Early infections, particularly on emerging cotyledons could lead to severe losses, even at this stage of the season," Gladders says.

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