|Crop Knowledge Master||Fungi|
|fruit and stem-and rot of papaya (Plant Disease Pathogen)|
Wayne Nishijima, Extension Plant Pathologist
Department of Plant Pathology
University of Hawaii at Hilo
This fungus has a wide host range around the world. However, the focus of this summary is its affect on papaya. In Hawaii, the only other known host of this fungus is cacao (Theobroma cacao).
This disease has been reported in Hawaii and India only, but unidentified Botryodiplodia spp. (synonym of Lasiodiplodia theobromae) have been reported from Brazil and Mexico causing papaya stem cankers. The fungus is found throughout the tropics and subtropics.
Fruit and stem-end rot is relatively minor but can be important under certain situations. The fungus is found throughout the tropics and subtropics causing numerous kinds of diseases but especially rots of fruits and root crops during storage. Although stem-end rots and body surface rots of papaya fruits in postharvest storage are the most common form of this disease the fungus is known to infect young, developing fruit in the field, presumably infecting through wounds.
The overall symptoms of this disease resemble dry rot caused by Mycosphaerella sp. but can be distinguished from dry rot by having a wider, more extensive translucent margin. It is a fast growing fungus and it is not unusual for it to rot and mummify the entire fruit. Gray mycelium forms over the infected area and later turns black from the masses of pycnidia that form. The infected flesh takes on a bluish-black discoloration in the soft water-soaked tissue. Air pockets often form in the infected area, presumably caused by the flesh shrinking, and later become filled with gray mycelium.
Sporulating lesions are black and have a rough surface caused by erumpent, confluent arrangement of pycnidia formed in stromata. Conidia are initially hyaline and unicellular, subovoid to ellipsoidal with a granular content. Mature conidia are two-celled, cinnamon to light brown in color and often with longitudinal striations. Conidia are 18-30 x 10-15 µm.
Stem-end rots caused by this fungus have been most troublesome on fruits that are vapor heated for fruit fly quarantine purposes. The single hot water postharvest dip (48ûC for 20 min) is effective in controlling this disease.
No specific control measures have been developed for this disease but field sprays with protective fungicides should reduce field inoculum levels and reduce disease incidence.
Alvarez, A.M., Hylin, J.W., and Ogata, J.N. 1977. Postharvest diseases of papaya reduced by biweekly orchard sprays. Plant Dis. Rep. 61:731-735.
Alvarez, A.M., and Nishijima, W.T. 1987. Postharvest diseases of papaya. Plant Dis. 71:681-686.
Gupta, O., and Nema, K.G. 1979. Effect of different temperature and relative humidity on the development of fruit rots of papaya caused by Botryodiplodia theobromae and Colletotrichum papayae. Indian Phytopathol. 32:106-107.
Hunter, J.E., and Buddenhagen, I.W. 1972. Incidence, epidemiology and control of fruit diseases of papaya in Hawaii. Trop. Agric. (Trinidad) 49:61-71.
Saldana, M.I., Marquez, M., and Ruiz, P. 1985. Identificacion de enfermedades fungosas del cultivo de la papaya (Carica papaya L.) en el estado de Tabasco. Revista Mexicana de Fitopatologia 3:14-17.