According to University of Idaho Potato Specialist Dr. Jeff Miller, the recent hot weather has reduced the favoribility of late blight. The 15-day forecast for southern Idaho is calling for the hot, dry weather to continue with temperatures reaching over 90 degrees Fahrenheit.
If an initial fungicide application has been made, subsequent application intervals can now be increased to 14 days. If thundershowers develop, returning to a seven- to 10-day interval is advised.
Miller also advises continued field scouting with the relaxed 14-day interval. If late blight is found, dispersal will be limited in the hot, dry weather even under irrigation. However, it is critical to know where outbreaks occur for the purposes of forecasting and spray recommendations.
In areas where late blight was observed in 2004, scouting for volunteers and any sign of late blight is recommended. If suspected lesions are found, please submit them to U of I personnel. The lesions should be placed in a plastic bag containing a damp (but not saturated) paper towel. This sample should be kept in a cooler or refrigerator if there will be a few hours between the time of collection and submission.
All information will be kept strictly confidential with findings reported only on a county basis. For more information, call University of Idaho Extension:
Treasure Valley: (208) 722-6701 (Mike Thornton)
Magic Valley: (208) 736-3600 or (208) 423-6621 (Nora Olsen)
Eastern Idaho: (208) 529-8376 (Phil Nolte), (208) 785-8060 (Bill Bohl), or (208) 397-4181 (Jeff Miller)