Accept cookies?

Our websites use cookies to deliver services to you on the internet. We do not use these to store personal information about you. Selecting Yes or No will set a cookie to remember your choice for this website.

YES     NO

Close this window   |  More information about our use of cookies.

Autumn disease assessment

Winter Oilseed Rape Disease Survey: Autumn assessment 2017/2018

Twenty-five plants from each surveyed crop were assessed visually for symptoms of disease at mid leaf production (December).

  • Ninety-one per cent of crops were affected with Phoma leaf spot in the autumn of 2017, this was higher than the previous autumn when 79% crops were affected. Within crops, 40% plants were affected with phoma leaf spot which was also higher than in the previous year when 27% plants were affected. Phoma leaf spot was recorded in all regions in the survey, with the highest incidence in the North and South East (where 100% crops were affected in both regions) whereas incidence across the rest of the country was uniformly consistent at 87% of crops affected. National severity was low, with 0.1% mean total leaf area affected.
  • Light leaf spot in the autumn was only recorded on plants in the North region, where there were 18% crops and 5% plants affected. This gave a national mean of 4% crops and 1% plants affected, which was lower than in the previous autumn when 10% crops and 1% plants were affected. The incidence of light leaf spot this autumn was also lower than the long-term mean (2005/6-2014/15) of 9% crops and 1% plants affected. The severity of light leaf spot in the North was 0.1% mean leaf area affected, but nationally less than 0.05% leaf area was affected.
  • Alternaria leaf spot affected 65% crops and 10% plants in the autumn of 2017, this was markedly higher than in the previous autumn when 44% crops and 4% plants were affected. Alternaria leaf spot was recorded in all regions in the survey. Regionally, the incidence of Alternaria leaf spot was highest in the South East with 90% crops and 18% plants affected and lowest in the North with 47% crops and 4% plants affected. The severity of Alternaria was low, with all regions having a mean of less than 0.05% total leaf area affected.
  • Downy mildew affected 28% crops and 5% plants this autumn which was very similar to the previous year when 29% crops and 4% plants were affected. The incidence of downy mildew this year was higher than the long-term mean (2005/6-2014/15) of 20% crops and 2% plants affected. Downy mildew was recorded in crops from all regions in the survey, except the South West. Regionally, the highest incidence was in the South East where 40% crops were affected. The severity of downy mildew was low throughout the country, with a national mean of less than 0.05% total leaf area affected.
  • Nationally, powdery mildew affected 19% crops and 5% plants this autumn, which was slightly higher than last year (when 14% crops and 2% plants were affected) but lower than the long-term mean (2005/6 – 2014/15) (20% crops and 7% plants affected). Powdery mildew was recorded at similar levels in all regions of the survey except the South West where it was not recorded on any surveyed crop. The severity of the disease was low, with a national mean of 0.1% mean leaf area affected.
  • Ring spot and Botrytis were not recorded on any surveyed crop this autumn.

Incidence of diseases on the leaf - % crops affected

Incidence of diseases on the leaf - % plants affected

Regional incidence of diseases on the leaf - % crops affected

Regional incidence of diseases on the leaf - % plants affected