Papaya Seedling Blight and Damping-off Caused by Colletotrichum gloeosporioides in Hawaii. J. Y. Uchida, Department of Plant Pathology, University of Hawaii, Honolulu 96822 . C. Y. Kadooka, and M. Aragaki, Department of Plant Pathology, and R. Manshardt, Department of Horticulture, University of Hawaii, Honolulu 96822. Plant Dis. 80:712. Accepted for publication 27 March 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0712A.
In 1994, a severe damping-off of glasshouse-grown, hybrid papaya (Carica papaya L.) seedlings occurred in the University of Hawaii at Manoa breeding program with over 80% mortality in some trays. Stem lesions were associated with Colletotrichum gloeosporioides (Penz.) Penz. & Sacc, in Penz. Nearly 90% of the specimens of hybrid Sunrise Solo x cv. #356 yielded Colletotrichum colonies from isolations. Two weeks after seeding, 30 to 40 healthy seedlings of hybrid Sunrise Solo x cv. #356 were inoculated with conidial suspensions of two single-conidial isolates adjusted to 106 spores/ml. Plants were kept at 100% relative humidity for 24 h and then returned to the glasshouse. Both isolates of C. gloeosporioides were pathogenic, causing cotyledon or leaf spots, defoliation, stem lesions, collar rots, and damping-off. Over 80% of the seedlings were diseased in 3 weeks. The fungus spread from leaf or cotyledon lesions to stems and eventually caused stem or collar rot and damping-off. Both isolates of Colletotrichum were reisolated and all control plants remained healthy. Similar results were obtained with the commercial cultivar Sunrise Solo. Major diseases of papaya caused by C. gloeosporioides in Hawaii have been anthracnose and postharvest fruit rots. This is the first report of severe papaya seedling losses caused by this fungus.