Phoma and light leaf spot

The most important foliar diseases of oilseed rape are phoma leaf spot/stem canker and light leaf spot. This page includes information about the diseases and their management (including the leaf spot forecasts)

Phoma leaf spot/stem canker

Leptosphaeria maculans and L. biglobosa

  • Often the most important disease in southern and eastern England
  • Can affect crops from emergence onwards
  • The fungus grows down the petiole and invades the stem to produce stem cankers that cause premature ripening and lodging
  • Plants with large leaves are less vulnerable than small plants
  • Managed at the leaf spot stage in autumn winter using resistant varieties and fungicide sprays

Phoma forecast

This forecast provides information on the date when 10 per cent of oilseed rape plants are expected to show symptoms of phoma leaf spot, generally regarded as the treatment threshold. The forecast uses temperature and rainfall data to simulate the development of the phoma fungus on crop debris and subsequent infection of young plants. The full model uses data from 01 July through to 26 September.

Click on the site "pointer" symbols to reveal phoma forecast information for that location. 

NOTE: Date ranges are displayed Month/Day/Year (US format)

Raw data (pdf)

1 = No symptoms. 2 = Infection started. 3 = 10% incidence. 4 = No data.

Light leaf spot

Pyrenopeziza brassicae

  • Historically, it was most serious in Scotland and the north of England
  • Has increased in importance in recent years throughout England
  • Risk can be predicted from disease levels on the pods of the previous year and summer temperatures
  • Managed using resistant varieties and fungicide sprays
  • Control may be affected by fungicide resistance but spray timing is more important

Light leaf spot forecast

Issued in autumn, the preliminary forecast shows the proportion of the oilseed rape crop (disease resistance rating of 5) estimated to have more than 25 per cent of plants affected by LLS in the spring for the current season. The forecast uses previous season pod incidence data, deviation from 30-year mean summer temperature data and 30-year mean rainfall data. In spring, the forecast is updated to reflect deviation in actual winter rainfall data from the 30-year mean.

LLS forecast maps, including the preliminary forecast for 2018/19

How risk compares to recent years. Download as a PDF.

Customised LLS forecast

To take account of variety, sowing date and autumn fungicide applications, produce a customised forecast to provide a better indication of risk.

Access the customised forecast service

You can register to be notified by e-mail when an updated forecast is released. You can also get updates via Twitter (@LeafSpot)