Oilseed rape growers are urged to inspect crops regularly after visible symptoms of light leaf spot were spotted at monitoring sites in both Yorkshire and Herefordshire.
“Disease incidence is currently in the region of 10% of plants affected and increases to more than 20% when plants are incubated,” said Julie Smith, plant pathologist with Adas.
“Light leaf spot can increase quickly and last year we saw the number of plants affected go from zero to 40% in two weeks in a susceptible variety,” she warned.
Phoma should also be a concern for growers in regions where autumn rain was sufficient to trigger the threshold required for infestation.
However, crops in the driest regions could now be the most vulnerable as they have not had the ability to grow away from the disease, warns Tim Nicholson, commercial technical manager with Bayer.
“In some areas such as Kent, it was so dry that development really stalled and small plants will still benefit from a phoma spray. Growers here need to be particularly vigilant,” he says.
Mr Nicholson advises that data from trial plots show that growers will see value in treating light leaf spot ahead of stem extension.
“If crops are showing signs of disease, my advice would be to treat if travel conditions allow. There’s no guarantee the conditions will be better at stem extension, and it might be too late if either disease gets established.”