Tag Archives: downy mildew

New diagnostic test for downy mildew

An AHDB Horticulture-funded study into reducing the cost of downy mildew control in onion crops has resulted in a new diagnostic test which will be available for growers to trial next year.

Dr Alison Wakeham of the University of Worcester explained the scientific work which has gone into developing the MILIONCAST (MILDEW on ONION FIRECAST) model which provides predictions of downy mildew sporulation based on environmental conditions.

However this cannot determine the disease is actually present, which is where the new hand held test comes in. An in-field air sampling device is collected and, “A five minute stick test shows if the disease is present in the [air]sample and at what level. As the level of the disease increases the strength of the line depletes,” explained Dr Wakeham.

In order to prevent different interpretations of the result due to differences in people’s eyesight a reader is used, although phone apps to read similar tests are becoming available. In trials using the test and the forecast model reduced the number of spays by half while maintaining control levels of the disease.

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New race of downy mildew recognised

The International Bremia Evaluation Board (IBEB) has officially designated a new race of downy mildew in lettuce: Bl:32. This isolate was already known, but has now become much more widespread in Europe, according to research by the IBEB into the Bremia isolates identified in 2014 and earlier. Most outbreaks of Bremia caused by these new isolates have only local consequences. In recent years, however, Bl:32 has been identified in France, Germany, The Netherlands, the United Kingdom, Austria, Switzerland and Belgium, and it has recently also spread to Portugal and northern Spain.

The IBEB is a joint initiative of lettuce breeding companies in France and the Netherlands, 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 European lettuce industry and promote the use of commonly accepted race names in communication with growers.

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