Nathan Kleczewski, Extension Specialist – Plant Pathology; nkleczew@udel.edu
For the second time in 3 years Nancy Gregory, diagnostician at the UD clinic, detected Phytophthora nicotianae on the foliage of potato plants. Unlike late blight, symptoms seem to be restricted to the lower canopy, close to the soil surface. The pathogen typically is found in the soil causing pink rot under hot, humid conditions and typically we do not see it on foliage. Continuous potato production and excessive warm, wet days are likely to result in this fungus making an appearance on foliage. Management for P. nicotianae on foliage is not required, but if detected it does indicate that you may have a greater potential for pink rot issues later in the season.