05/17/07 Potato late blight forecast

Washington Ag May 17, 2007 The Columbia Basin late blight forecasting model is predicting that late blight will occur this year again in the Basin. However, Washington State University plant pathologist Dennis Johnson says on the Late Blight Hotline that the probability of late blight is in the lowest in several years. Johnson: "Probability at present is near 75 percent and the probability will increase with anymore rainfall in May. The current probability is less than what it has been in the Basin for the last five years." No late blight has been reported in the Basin so far but Johnson says sprinkler irrigated fields should be treated with a protective fungicide for late blight at row closure and then seven days later. Johnson: "If the application seven days after row closure coincides with full bloom of primary flower clusters a fungicide effective against both late blight and scerlitini stem rot, such as Omega, would offer protection against both diseases." Johnson says rill irrigated fields do not need to be treated for late blight at this time. He also emphasizes the need to control volunteer plants particularly in fields that had late blight in them the past two years. I'm Bob Hoff.