01 Jul 2019

Denomination of a new official race of downy mildew in lettuce, Bl:36

With effect from 01 July 2019 the International Bremia Evaluation Board Europe (IBEB-EU) has designated a new official race of downy mildew in lettuce, Bl:36EU.

This new race of lettuce downy mildew pathogen (Bremia lactucae, Bl) has been identified in recent years; Bl:36EU was first encountered in Germany in 2016, and over recent years it was found throughout Europe (France, the Netherlands, Italy, Switzerland and Scandinavia).


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 standardised 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.

Managing Downy Mildew

Rijk Zwaan’s lettuce program has a range of varieties resistant to Bl:36EU, 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 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:36EU, please see the official press release, or contact your local sales representative.

For more information