Jul 26, 2016Late blight spreads in Columbia Basin
Dennis Johnson, WSU professor and Extension plant pathologist, reported the following information in the alert.
Late blight has spread and is extensively present in fields near Burbank, northeast of Pasco, north of Pasco, and north to Eltopia. The strain of the late blight pathogen in the Basin this year is US8, which is resistant to metalaxyl. A serious storage problem, due to tuber infection is potentially ahead for this fall. Monitor fields thoroughly for late blight so you know what you are up against. Fields with late blight should be on a 5 day application schedule. Fields adjacent to infected fields should be on a 5 to 7 day application schedule. All sprinkler irrigated fields in the Columbia Basin should be on at least a 7 to 10 day application schedule. Water needs for many potato crops at this time are decreasing so do not over water. All fields, including rill irrigated fields in the Columbia Basin should be treated with a fungicide before any rainfall. Monitor fields for late blight and watch the weather forecasts for rain.
A recent Potato Progress article, Fungicide Application for Management of Potato Late Blight in the Columbia Basin by Johnson, Philip B. Hamm and Jeffrey S. Miller, has detailed information to help manage the disease.