Downy mildew explosion in seed onions

In recent years, onion growers had little trouble with it, but downy mildew can now be found in almost every block of seed onions. In the worst cases, it can lead to significant yield loss. Downy mildew also has a high risk of infection in the coming days.

There have been plenty of infection opportunities for downy mildew lately. Finding a pipe here and there with a small infestation of downy mildew is not a disaster, but the onion grower must remain alert when it is found and adhere to a strict spraying schedule.

Downy mildew under control
Reports are coming in about downy mildew from all over the Netherlands, says Andre Boot, Hazera's crop specialist on onions. This varies from minor infestations to major problems, which can lead to significant yield losses. The Gewastour onion growers also occasionally find some mildew, but so far it has not caused any problems. 'Some spots have been found in our plot, but that is under control,' reports onion grower Harmjan Hospers from Nagele. On the plot in Kimswerd, onion grower Reinder Hogenhout also occasionally finds a pipe with downy mildew and sees it much more than in recent years.

Mildew strikes easier due to stemphylium
The leaf spot disease stemphylium makes it a lot easier for downy mildew, says Andre Boot: 'After the warm days you see that the crop develops yellow tips and you see quite a lot. This is not only because of a moisture deficiency, but also the leaf disease stemphylium. That is not a problem if you follow a correct spraying schedule. However, those are precisely the places where downy mildew can strike more easily.' 

More information about leaf spot diseases in seed onions can be found in the video from Bayer Cropscience, with Mark Ermers.

Jesse Torringa

Jesse is an editor at Boerenbusiness and focuses in particular on the arable farming sector, including grain and onions. He also closely follows the fertilizer market. In addition, Jesse works on an arable farm in Groningen with seed potatoes as the main branch.

j.torringa@boerenbusiness. Nl

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