News - 02-07-2025
New race of downy mildew in the USA
There is a new downy mildew race in the USA, that has not been detected Australia or Europe and is not considered a threat to the local market.
The International Bremia Evaluation Board (IBEB) is an organisation that monitors and designates new races of Bremia lactucae in Europe.
IBEB works internationally through regional boards, including IBEB-EU (Europe) and IBEB-US (United States), to standardise race names and communication with growers. Australia does not currently have its own IBEB board.
On 1 July, the International Bremia Evaluation Board (IBEB) released its latest updates on lettuce downy mildew (Bremia lactucae) activity – with important findings from both Europe and the United States.
In Europe, the IBEB-EU confirmed that no new official race has been identified.
In the United States, the IBEB-US has officially denominated a new race.
Bl: 10US, now widespread in California and relevant to the US and Mexican markets.
Importantly for Australian growers, Bl:10US has not been detected in Australia and is not considered a local threat.
Our breeding programs at Rijk Zwaan continue to stay ahead of emerging strains, and many of our varieties already include resistance to US races BI: 7 to 10US, offering reassurance for export-linked supply chains.
The most significant strains currently impacting Australian crops remain Bl: 41EU, alongside Bl: 37EU, 38EU, 39EU and 40EU. These races continue to be actively managed across Australian growing regions, and Rijk Zwaan’s lettuce range includes varieties with resistance to these key strains.
While no crop is immune to downy mildew, using highly resistant varieties - like those from Rijk Zwaan - alongside proper preventive practices offers the best strategy for successful lettuce production.
Lettuce varieties have developed at Rijk Zwaan’s research and breeding station in the Netherlands and trial stations in Australia, are tailored to our diverse growing conditions and cultivation methods , as well the unique pests and disease threats faced by growers in Australia.
Rijk Zwaan remains committed to sustainable solutions, with strong focus on resistance breeding, integrated disease management, and grower support. Our crop specialists are available to help growers select varieties best suited to local conditions and disease pressures.
For more information about Bremia-resistant varieties, take a look at our lettuce assortment, or reach out to your local Rijk Zwaan representative.
Contact:
Rob Philip
+614 2757 6044
r.philip@rijkzwaan.com.au
Published: 02/07/2025
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