Late blight

Late blight (Phytophthora infestans) is a highly destructive oomycete disease affecting potatoes, tomatoes, and other solanaceous crops. Symptoms begin as dark, water-soaked greenish-gray spots on leaf surfaces, rapidly expanding into dark brown to black necrotic lesions with chlorotic borders. Under humid conditions, a fine white mold-like growth (sporangia) forms on the underside of the leaves, leading to rapid leaf collapse, tissue rot, and widespread plant destruction.