A bumper year for light leaf spot on Oilseed Rape in 2012

Fera has published the latest results from the Defra Winter Oilseed Rape Pest and Disease survey showing that light leaf spot disease levels in oilseed rape crops during pod ripening were the highest ever recorded.

Levels of light leaf spot have been increasing steadily year-on-year

Levels of light leaf spot have been increasing steadily year-on-year since the very low levels recorded in 2004, and levels of disease on the stems in 2012 were the highest recorded since the survey began in 1987. In recent years, phoma canker has been the most prevalent disease, but levels have started to decline and light leaf spot has this year gained predominance as the most common disease on oilseed rape. At pod ripening, light leaf spot was present in 97% of the crops surveyed with 82% of crops showing symptoms on the pods. Regional analysis shows that the few crops which remained unaffected by the disease were in the Eastern region and confirms the historic trend of the disease being more prevalent in the North and West of the country. At the start of the 2011-2012 growing season, light leaf spot levels were slightly lower than those seen in previous years. However, it was during stem extension in the spring when these levels started to increase, with incidence at this point being the second highest recorded since the survey began. As the disease favours cooler, wetter conditions disease levels continued to rise throughout the remainder of the season.

Levels of Sclerotinia, Botrytis and Alternaria were also much higher than those seen in previous years. Sclerotinia stem rot affected 10% of crops in the survey – the highest incidence since 2008. On the pods, Botrytis affected 91% crops – the highest incidence since 2005 and on the stems, Botrytis affected 34% crops – the highest incidence since 1991. Alternaria pod spot affected 76% crops – the highest since 2007. Regionally, it was the Midlands and West which had the highest incidences of all three of these diseases.

More detailed information on results from the survey is available via the CropMonitor website at: www.cropmonitor.co.uk.

• Annual monitoring of winter oilseed rape diseases is carried out by Fera in collaboration with ADAS and NIABTAG as part of the national crop pest and disease surveys funded by Defra. The incidence of diseases was assessed in approximately 100 commercially grown winter oilseed crops which were selected at random from a list of farms stratified by region and farm size. The fields were sampled by collecting 25 plants at random from a diagonal transect of the field. Crops were sampled during leaf development, stem extension and pod ripening.
• The Food and Environment Research Agency (Fera) is an Executive Agency of the UK Government’s Department for Environment, Food and Rural Affairs (Defra). Its remit is to provide robust evidence, rigorous analysis and expert professional advice to government, international organisations and the private sector, in order to support and develop a sustainable and secure food chain, a healthy natural environment, and to protect the global community from biological and chemical risks.