Climatic conditions in Iowa are generally unfavorable to the development of the potato disease known as late blight. It is of rare occurence here but in occasional seasons it causes serious losses.

The climatic conditions under which late blight occurs in Iowa are a high degree of humidity with heavy dews and midsummer temperatures lower than usual. An excess of rainfall and a predominance of cloudy weather are contributing factors.

The practice of shipping in northern grown potatoes for seed is common in Iowa. Such seed is apt to be infected with the late blight fungus.