Spring disease assessment

Brown rust risk map
Spring disease assessment
Winter Oilseed Rape Disease Survey: Spring assessment 2018

Twenty five plants from each surveyed crop were assessed visually for symptoms of disease at early stem extension.

  • Light leaf spot affected 64% crops and 15% plants this spring, which was just slightly lower than last year (68% crops and 15% plants affected). Light leaf spot was the most severe disease in the survey this spring, affecting 0.5% total leaf area, which was more severe than last year when the severity was 0.2% total leaf area affected. The disease affected crops in all regions, with the North showing the highest incidence (88% crops and 40% plants affected) and also the greatest severity (1.9% total leaf area affected).
  • Phoma leaf spot affected 90% crops and 32% plants, which was slightly lower than last year when 91% crops and 36% plants were affected. Severity of the disease was low, with a national mean of 0.1% total leaf area affected – the same severity as last year. Phoma leaf spot affected crops in all regions with the Midlands & West and South West having 100% crops affected. The region with the lowest incidence was the South East, with 80% crops affected.
  • Nationally, Alternaria leaf spot affected 30% crops and 2% plants this spring, which was very higher than last year when 20% crops and 2% plants were affected. Alternaria leaf spot was recorded on crops in all regions in the survey, with the exception of the North. The South West had the highest incidence with 63% crops and 8% plants affected. Severity of the disease was low, with all regions having a mean of less than 0.05% total leaf area affected.
  • Downy mildew affected 16% crops and 1% plants this spring. This was very similar to last year when 17% crops and 2% plants were affected. The disease was recorded in all regions in the survey this spring with the exception of the South West. The region with the highest incidence was the South East with 30% crops and 1.6% plants affected. Severity of the disease was low, with a mean of less than 0.05% total leaf area affected in all regions.
  • Powdery mildew was not recorded on any surveyed crop this spring.
  • White leaf spot, ring spot and botrytis were also not found in any surveyed crop this spring.

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