Oilseed rape growers are being warned the danger of light leaf spot hitting crops is at the highest level for large parts of the country.
Regional forecasts predict more than 60% of crops are likely to have more than 25% of their plants affected by light leaf spot in all areas of Britain apart from East Anglia and south England, where the incidence level is expected to be lower.
This is the third year running the risk of the fungal disease has been at its most severe level, with regional risk levels broadly similar to that of a year ago.
“Many factors influence the risk of disease development and we are reminding people to visit the light leaf spot web page to build a customised forecast,” said plant pathologist Neal Evans, who put together the forecast using Rothamstead Research data.
Dr Evans explained the best way to know what is happening on a field-by-field basis was to take plant samples, and put them in polythene bags at 10-15C for four to five days to bring out the symptoms.
Crops most at risk are varieties with a resistance rating below six which have not received a phoma spray, so the disease can be detected and sprayed before it becomes established.
Controlling the disease
Paul Gosling, who manages the fungicide performance work at AHDB explained their fungicide performance trials showed several products can achieve similar control levels.
“Product choice will be ultimately guided by other considerations, such as product activity against phoma leaf spot and plant growth regulatory activity,” he added.
Growers looking for more information are advised to visit the AHDB disease management web page.