Scab of cucurbits
On leaves, slightly water-soaked or pale-green spots are the first symptoms. These spots are usually numerous and can appear on and between veins. Similar, elongate spots may develop on stems and petioles. Spots gradually turn grey or white and become roughly circular to angular, often with yellow margins. They are superficially similar to those caused by angular leaf spot. Fine veinlets in the spots may remain brown or tan and are distinct against a white background.