Alternaria leaf blight of Cucurbits

Another name for this disease is target leaf spot which refers to the appearance of the lesions on the upper surface of the leaves. Lesions tend to appear first on the older leaves as small circular spots. The spots are light brown with a light center and form concentric dark rings as they enlarge, thus the name target spot. Lesions which form on the lower leaf surface tend to be more diffuse. Fruit infections begin as sunken brown spots and may later develop a dark powdery appearance as the fungus sporulates. The infection may also begin at the blossom end with the entire fruit eventually turning brown and shriveling.