Late blight was confirmed in the Columbia Basin June 25 at two locations; south of Kennewick (Horse Heaven Hills) and near Burbank, Wash. There are few additional details at this time.
The weather conditions this spring in Idaho have been extremely favorable for late blight to become established. Potatoes need to be protected beginning at row closure. Protectant fungicides (EBDC and chlorothalonil) are recommended on a 10–14 day schedule while vines are actively growing. These products will also provide some protection against early blight and brown leaf spot. At this point in time, these products will provide good preventative protection. If late blight is found in southern Idaho, then more a more aggressive approach may be necessary.
Use of Omega for white mold control provides protection against late blight. While Endura is highly effective against early blight and white mold, it is not effective against late blight. Revus Top is effective against both early blight and late blight. Gavel, Ranman, Forum, Previcur and Curzate are also highly effective against late blight. Tanos is a combination of a QoI fungicide and Curzate. Use of a phosphorus acid product may be beneficial for protecting tubers against late blight and pink rot. A more complete discussion of different fungicides and their relative strengths can be found at:
Oregon Hot Line is (800) 705-3377
Washington (800) 984-7400
Source: Philip B. Hamm, Superintendant at the OSU Hermiston Agricultural Research & Extension Center.