VIEW ARTICLE

Factors Affecting Postharvest Development of Collectotrichum gloeosporioides in Citrus Fruits. G. Eldon Brown, Plant Pathologist III, Florida Department of Citrus, University of Florida, Institute of Food and Agricultural Sciences, Agricultural Research and Education Center, P.O. Box 1088, Lake Alfred 33850; Phytopathology 65:404-409. Accepted for publication 18 October 1974. DOI: 10.1094/Phyto-65-404.

Appressoria of Colletotrichum gloeosporioides were often very numerous in localized areas on the surface of citrus fruits. Most appressoria did not produce infection hyphae, and those hyphae that were formed caused only a latent infection before fruit maturity. Such hyphae were thin, thread-like, less than 1.0 µm in diameter, and were observed within or beneath the cuticle, intercellularly in the epidermis, or inter- and intracellularly in the upper two-to-four cell layers of the flavedo. Ethylene-degreening treatment of mature Robinson tangerines stimulated appressoria to form infection hyphae, thereby causing an increased incidence of anthracnose. This effect was greater when an ethylene concentration of 50 µliters/liter of air rather than 5 µliters/liter of air were used. Washing the tangerines before degreening removed many of the appressoria and thereby reduced anthracnose severity. Infections established before harvest frequently did not provide sufficient latent inoculum to induce anthracnose.