Jun 9, 2016
Washington state late blight strain identified

Dennis Johnson, Washington State University plant pathologist, said that the late blight reported in Washington state last week has been identified as the US8 strain, which is mefenoxam and metalaxyl resistant.

The strain was found in Walla Walla County near Burbank, Washington.

US 8 and US 23 were both present in the Columbia Basin last year. Temperatures are moderating and the expected mild conditions in the Basin will favor heavy sporulation. Rain, cloudy conditions, and frequent sprinkler irrigation will promote late blight infections. Johnson recommends fields with late blight should be on a 5-day application schedule and sprinkler irrigated fields in the Burbank, Finley and north Pasco areas should be treated with a late blight fungicide on a 7-day schedule.

All fields, including rill irrigated fields in the Columbia Basin should be treated with a fungicide 0 to 7 days before any major rainfall (by zero, I mean the day of rain). Monitor fields for late blight and watch the weather forecasts for rain, Johnson said. Volunteer potatoes and refuse tubers need to be managed. Late blight must be managed on a regional basis to effectively control the disease, Johnson said.

Contact Dennis Johnson at 509-335-3753 or [email protected] to report, confirm, or make a late blight diagnosis. The hotline number is 1-800-984-7400.


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