Late Blight Found In Southern Idaho

Late blight was confirmed in Canyon County on the morning of July 19th. The infected area appeared to have started from a drowned-out spot. Lesions were scattered throughout the field and another field had a very light infestation.

Initially, the infected leaves didn't show the light-green halo. The characteristic halo appeared after the leaves had dried out. White sporulation was visible on leaves in the early morning dew.

Treasure Valley growers are advised to spray protective fungicide immediately if no applications have been made, and to continue applications on a weekly basis. Spread of the pathogen will be slow as long as the weather remains hot and dry.

Intensive scouting is recommended. The late blight was likely present for some time but limited in expression because of the hot, dry weather.

Spring weather was extremely favorable for late blight establishment. The threat remains high for all areas of the state and will likely appear in other areas soon. Growers should scout wet areas in fields two-to three-times per week.