Thanks to Sandesh Dangi of Phil Wharton’s lab (Univ. of Idaho) for determining that the fields with late blight in Minidoka County are the US-23 genotype.
Most isolates of the US-23 genotype can be managed with mefenoxam or metalaxyl (Ridomil and similar fungicides). Mefenoxam/metalaxyl are highly systemic and are highly effective in reducing sporulation of the pathogen. Other fungicides which have been shown to be highly effective against the late blight pathogen include Orondis, Revus, Zing or Gavel, Ranmam, Omega, Previcur, Forum, Curzate and Tanos, and Ariston.
Phosphite-based fungicides are not effective against foliar late blight but are effective in protecting tubers. If tuber infection is feared for tubers destined for storage, then post-harvest applications of phosphite fungicides (e.g. Resist 57, Phostrol, Phiticide) can be highly effective.
Protectant fungicides such as chlorothalonil and mancozeb can be effective in dry weather conditions.
A discussion about the pros and cons of different fungicides can be found here:
Please bring in samples to the University of Idaho or Miller Research if you have any questions about whether late blight is present in your field or not.
