We have two leaf diseases of potatoes in Iowa which can reduce the yield and increase spoilage of stored potatoes. These are early blight and late blight. You can prevent most of the damage from these diseases by spraying the growing crop.
Hooker, W. J.; Buchholtz, W. F.; and Coe, D. M.
"You Can Whip Potato Blight,"
Iowa Farm Science: Vol. 4
, Article 5.
Available at: https://lib.dr.iastate.edu/farmscience/vol4/iss12/5