Late Blight Forecast: So Far So Good
As of July 5th, late blight has not been reported in southern Idaho. The last several days have been warm and dry.
A seven to 10 day protectant spray program at row closure is still recommended. University of Idaho Potato Specialist Dr. Nora Olsen advises growers to carefully scout areas where irrigation overlaps occur, pivot centers, low-lying areas, and other spots where additional water may be present.
Late blight symptoms include water soaked-lesions on the undersides of leaves that may produce spores. Growers should also watch for blackish-colored lesions on stems, meristems and petioles.
Low numbers of green peach aphids have been spotted in the Treasure Valley. Scouting should also entail looking for aphids on the underside of leaves in the middle of the canopy.
July 5th was the 10th anniversary of having late blight in Idaho. The industry has learned a lot since then and Scouting and timely fungicide applications are the best tools.
If you see symptoms that you think might be late blight, please contact University of Idaho personnel: Mike Thorton (722-6701) in western Idaho, Nora Olsen (736-3600) in the Magic Valley, and Jeff Miller (397-4181), Bill Bohl (785-8060), or Phil Nolte (529-8376) in eastern Idaho. All information submitted to the University of Idaho will be kept in strict confidentiality and results will only be reported on a county level.