No new official downy mildew race in Europe

Downy mildew can affect lettuce leaves in both protected and open-field crops, resulting in production losses. New variants of downy mildew (Bremia lactucae or Bl) often emerge during the cultivation cycle. But on 1 July this year, the International Bremia Evaluation Board Europe (IBEB-EU) announced that no new Bremia variants found in practice in Europe over the past year were deemed significant enough to warrant an official denomination.  

Based on research into Bremia, the IBEB-EU concluded that the race Bl: 41EU continues to play an important role in the downy mildew outbreaks. Additionally, Bl: 37EU, Bl: 38EU, Bl: 39EU and Bl: 40EU are significant. Rijk Zwaan’s crop specialists are happy to advise growers with detailed information about the company’s range of lettuce varieties and their resistances against these races and other diseases. 

Rijk Zwaan's research and breeding station in Fijnaart, the Netherlands. The company has more than 500 lettuce varieties, tailored to various cultivation methods and environmental conditions and with various resistances.  

Sustainable solution  

In its breeding activities, Rijk Zwaan focuses heavily on resistances to make plants resilient against diseases such as downy mildew. The company is a strong advocate of integrated pest management to minimise the risk of plant-disease outbreaks. Resistant varieties play a crucial role, but Rijk Zwaan also advises growers the restrained use of appropriate crop protection agents to prevent the emergence of new downy mildew variants. Furthermore, the implementation of good hygiene practices – such as removing diseased crops and rapidly ploughing in crop residues – can help to reduce the spread of downy mildew in lettuce. 

International Bremia Evaluation Board  

The International Bremia Evaluation Board (IBEB) is a joint initiative of lettuce breeding companies in the USA, France and the Netherlands, plus the University of California-Davis, the Netherlands’ Inspection Service for Horticulture (Naktuinbouw) and the French National Seed Station (GEVES). IBEB's mission is to identify new Bremia lactucae races that pose a significant threat to North American or European lettuce production, and to promote the use of standardised race names in communication with growers. Races are identified and denominated by regional, continent-specific IBEB committees. For more information, visit the International Seed Federation’s website.  

Denomination of a new Bremia race in the USA  

On 1 July, the US committee of the International Bremia Evaluation Board (IBEB-US) did publish the denomination of a new race of downy mildew in lettuce occurring in the western US: Bl: 10US.