fruit spot, symptom of plant disease, usually caused by fungi and bacteria. A spot is a definite, localized area. Spots frequently enlarge and merge to form a rot, a softening discoloration and often a disintegration of tissue. All fruits are susceptible; infection commonly starts at a wound, the stem end, or the underside. Bacterial decays that are caused by Erwinia and some Pseudomonas species are watery to mushy and putrid and follow injuries. Other bacterial and fungal decays (except Pythium and Phytophthora) are generally firm and dry. Fruit-infecting organisms may attack other plant parts. Insects commonly transmit the infecting microorganisms and provide the entry wounds. Spots and rots develop rapidly in warm, moist storage. See also rot; scab; sooty mold.