Phlox sp. (Phlox) has several foliar diseases but the most common is powdery mildew. Buy resistant varieties. Improve sunlight and air circulation. Fungicides and sanitation are helpful.
Written by James Schuster, Extension Educator, Horticulture, and reviewed by Bruce Paulsrud, Extension Specialist, Plant Pathology and Phil Nixon, Extension Entomologist, University of Illinois at Urbana-Champaign.