Onion Growers Asked to Watch for Downy Mildew, Iris Yellow Spot

Washington State University is warning onion growers to be vigilant with their disease management.  WSU Extension’s Tim Waters told the Washington Ag Network one of the chief concerns is Downy Mildew, which is a water mold like Late Blight

“Conditions that promote Late Blight in potato are also going to promote Downy Mildew in Onions; so cool wet conditions.  And we had those conditions this spring.  Downy Mildew typically is found in seed crops, onion seed crops to some extent, but last year we started finding it in bulb crops, and it was pretty wide spread.”

Waters says they suspect with the weather the Columbia Basin experienced this spring, they will see several cases of Downy Mildew.  Already this year, one case has been reported on the northern portion of the Basin.

“So, it is out there, in a relatively low level, but it’s going to be an important one for people to watch out for especially in center pivots irrigated fields.  That leaf tissue is staying wetter longer, and that’s going to promote growth of that pathogen”

Waters added they’ve found a few cases of iris yellow spot virus, which is typical for this time of year.  He says bulb growers need to be maintaining their thrips to reduce movement of the virus.

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