Common Signs and Symptoms of Plant Disease Unhealthy plants have special distress signals that let you know when pathogens have attacked. Plants will respond to the stress of infection with a wide range of symptoms, from leaf spots and damaged fruit to wilting and even death. To help narrow down your diagnosis, see if any of the descriptions below match the affected parts of your plant. Blights Leaves, flowers, stems, and branches that suddenly wilt, wither, and die are common indications of blight. Common garden blights include Botrytis, early and late blight (caused by fungi), and fire blight (produced by bacteria). Cankers Affected woody plants produce dead, and often sunken, patches in stems and branches. These cankers may ooze a sticky or foul-smelling material and can spread to kill whole trunks or shoots. The fungal Cytospora canker is a common orchard problem: bacterial fire blight is another canker-causer. Galls Swellings or overgrown patches of leaf or stem tissue are commonly known as galls They may be caused by fungi (like leaf gall) , bacteria  (such as crown gall), or even insects (such as gall wasps). Leaf Curl Deformed and discolored leaves suffer from leaf curl. Peach leaf curl  is caused by a fungus; viruses may also produce these symptoms. Leaf Spots Rounded or irregular areas n various colors are common leaf symptoms. They are produced by many pathogens. Mildews Dusty white, gray, or purplish patches on the surfaces or undersides of leaves are an easy clue to the fungal  powdery and downy mildews. Rots Soft or discolored and dying plant tissue generally indicate some kind of rot. Fungi and bacteria can cause rot on fruit, stems, flowers, or roots. Rusts Orange or yellowish spots, galls,or coatings are caused by rust fungi. Rusts may affect leave, stems, flowers, or fruits. Wilts Drooping leaves and stems indicate that the plant isn't getting enough water. This may be caused by improper watering or by fungi and bacteria that can clog the plant's water conducting system.Fungi cause Fusarium and Verticillium wilt; bacterial wilt is a problem in cucumbers and related crops.