|Crop Knowledge Master||Fungi|
|internal blight of papaya (Plant Disease Pathogen)|
Wayne Nishijima, Extension Plant Pathologist
Department of Plant Pathology
University of Hawaii at Hilo
Internal "blight" is a disease of papaya fruit that occurs when one of several fungi enter the seed cavity and cause an internal infection. Although this is the most common fungus involved, both Fusarium sp. and Penicillium sp. are occasionally recovered from diseased fruit.
Although Cladosporium sp. has only been reported to occur on papaya in Hawaii, other Cladosporium spp. occur widely in other states, causing a variety of diseases on many different hosts.
Infected tissue is watersoaked and translucent in the early stages to black and firm in the later stages of infection. Infected fruits yellow prematurely and unevenly in the fruit column. People harvesting or packing papaya fruits, therefore, can easily recognize infected fruits and cull them.
Once inside the seed cavity the fungus grows through the mucilaginous coating surrounding the seeds, causing it to shrivel, dry and darken. The entire seed cavity is usually colonized and the adjacent flesh also can be infected.
Apparently, the incomplete closure of the blossom end is genetically controlled thus proper seed selection, i.e. consistently selecting seeds only from trees on which this problem does not occur, is important in minimizing this disorder.
Preventive field sprays can reduce inoculum level in the field.
Hine, R.B., Holtzmann, O.V., and Raabe, R.D. 1965. Diseases of papaya (Carica papaya L.) in Hawaii. Hawaii Agric. Exp. Stn. Bull. 136, Univ. of Hawaii, 25 pp.
Zee, F.T., Nishina, M.S., Chan, H.T., and Nishijima, K.A. 1989. Blossom end defects and fruit fly infestation in papayas following hot water quarantine treatment. HortScience, 24:323-325.