Another quiet week on the late blight front in Idaho. However, on 10 August 2020, late blight was confirmed on potato in Adams County, Wisconsin. The strain was genotyped as US-23. The lesions, on leaves and stems, were found on very few plants in one isolated area. The infection was estimated to be less than one week old. Only in the 48hrs before the outbreak was discovered had the weather become favorable for late blight with the weather hot and dry and not favorable for late blight in the weeks prior to that. This should be a reminder that with pop up thunderstorms in the area, the weather conditions can rapidly change and become favorable for late blight disease development.
Spores of Alternaria solani (early blight) were detected at Parma (6 days) and Acequia (3 days). Spores of S. sclerotiourm (white mold) were detected at Idaho Falls (3 days), Parma (1 day), Acequia (1 day), Rupert/Paul (1 day), Rexburg (2 days), Ashton/Tetonia (3 days) and Blackfoot (6 days).
None of the weather stations in Idaho reported any days where the number of hours of relative humidity above 80% were above 10 hrs.