Bacterial Leaf Spot on Greenhouse Ornamentals
Typical leaf spots caused by bacteria appear as water-soaked, brown to black lesions often outlined with a yellow halo. Water-soaked (or sometimes called greasy) spots often appear on the underside of the leaf first. Lesions caused by Xanthomonas on Begonia and Pelargonium are v-shaped, extending inwards from the leaf margin. Necrotic spots may be angular or somewhat round. Spots may coalesce to cause a blighted appearance in some hosts. Bacterial leaf spots can easily be confused with fungal leaf spots, so be sure to get plants diagnosed by a plant disease clinic (NCSU Plant Disease Clinic).