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02 Jul 2018

Denomination of new official races downy mildew in lettuce, Bl:34EU & Bl:35EU

With effect from 02 July 2018 the International Bremia Evaluation Board Europe (IBEB-EU) has named two new official races of downy mildew in lettuce, Bl:34EU & Bl:35EU.

New official strains

These new races of lettuce downy mildew pathogen (Bremia lactucae, Bl) have been identified in recent years; Bl:34EU was first identified in Belgium in 2015, and has been since found in many  countries in Europe;  Bl:35EU was first identified in France in 2015, and has been since found in Belgium, the Netherlands, UK, & Germany.


The International Bremia Evaluation Board (IBEB) is a joint initiative of lettuce breeding companies in USA, France and the Netherlands, University of California-Davis, the Dutch inspection service (Naktuinbouw) and the French National Seed Station (GEVES). IBEB’s mission is to identify new races of Bremia lactucae that pose a significant threat to the American and European lettuce industry and promote the use of standardized race names in communications with growers. The race identification and nomination is done by regional IBEB committees specific to each continent. For more information see the ISF website

Integrated Resistance Management

Rijk Zwaan’s lettuce program has a range of varieties resistant to Bl:34EU and Bl:35EU, other official strains, and in many cases to other local isolates. For the most up to date information on varietal performance and downy mildew, we recommend that growers speak to their local sales representative.

As the spread of this new strain is mainly limited to Europe it is not of major significance to Australian growers.

However, the announcement of a new strain serves as a reminder that although Rijk Zwaan as a breeding company endeavours to supply growers with lettuce varieties resistant to all official strains and locally discovered isolates, this is not always full insurance against downy mildew outbreaks.

Rijk Zwaan advocates an integrated approach to disease control; resistant varieties are a large part of this, but crop protection agents and hygiene measures are also important to help prevent the development of new downy mildew races. Proper hygiene practices, such as removal of debris and diseased plants, will reduce the spread of downy mildew in crops.

For more information on Bl:34EU & Bl:35EU please see the official press release, or contact your local sales representative.

Download the Plantum Press Release