Late blight is present in a number of fields north of Pasco up to at least Eltopia and east of Pasco to the Snake River. The strain of the late blight pathogen is US8. This is metalaxyl and mefenoxam resistant. Do not use Ridomil.
Fields with late blight and adjacent fields should be on a 5 to 7 day fungicide application schedule. Fields north of Pasco to Mesa and east of Pasco to Eureka and Burbank without late blight should be on a 7 day schedule. Other fields in the Basin should be treated at row closure and then on a 10 to 14 day schedule. Monitor fields for late blight and please keep us posted of any new developments. Collections are needed to determine the genotype.
Please contact Dennis Johnson at 509-335-3753 or dajohn@wsu.edu to report, confirm, or make a late blight diagnosis. We need to have samples tested to determine the strain so we know which fungicides will be effective.
Originally posted by Dr. Dennis Johnson’s late blight hotline, that was updated on July 12, 2017.
