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Two Bacterial Diseases of Papaya Trees Caused by Erwinia Species in the Northern Mariana Islands. E. E. Trujillo, Professor, Department of Plant Pathology, University of Hawaii, Honolulu 96822. M. N. Schroth, Professor, Department of Plant Pathology, University of California, Berkeley 94720. Plant Dis. 66:116-120. Accepted for publication 16 April 1981. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-116.

An Erwinia sp. was the cause of blackish, water-soaked, mushy cankers that occurred near or in leaf axils of upper portions of papaya stems in the northern Mariana Islands. This disease was prevalent on wild and commercial papaya trees after near-typhoon storms. The pathogen gained entrance through wounds caused by wind damage to the foliage. A different Erwinia sp. was the cause of a systemic blight of papaya resulting in rapid decline of commercial orchards. Symptoms of this disease were dark, angular, greasy, water-soaked lesions on the underside of the leaf causing chlorosis and necrosis of the foliage. Water-soaked lesions on petioles and upper portions of the stems were followed by systemic invasion and rot of the tree top and finally tree death in less than 6 wk. The African snail Achotina fulica, a vector of the decline Erwinia sp., spread it from diseased to healthy trees in the feeding process. The decline Erwinia sp. was recovered from the fresh excreta of snails collected from diseased trees. High resistance to the pathogen was observed in wild papaya trees of the northern Marianas. Commercial varieties tested showed high to low susceptibility. Kapoho Solo, one of the most important commercial lines in Hawaii, was highly susceptible. The two Erwinia pathogens do not correspond with any of the defined Erwinia species and subspecies. The diseases are referred to as the Erwinia mushy canker disease of papaya and the Erwinia decline disease of papaya.