Limitations of Hot Water Treatment in the Control of Phytophthora Fruit Rot of Papaya. M. Aragaki, Plant Pathologist, Department of Plant Pathology, University of Hawaii, Honolulu 96822. W. S. Kimoto, Research Assistant, and J. Y. Uchida, Research Associate, Department of Plant Pathology, University of Hawaii, Honolulu 96822. Plant Dis. 65:744-745. Accepted for publication 7 January 1981. Copyright 1981 American Phytopathological Society. DOI: 10.1094/PD-65-744.

A destructive epidemic of Phytophthora blight of papaya occurred in Hawaii in the spring of 1979. Fruit rots, which were usually controlled by field fungicide applications and postharvest hot water treatment, developed in large numbers. Possible causes for the failure to control fruit rots were tested experimentally and discounted, including failure to maintain minimum specifications for temperature and time of hot water treatment; development of a strain of Phytophthora palmivora tolerant to high temperature; and introduction of P. parasitica or P. capsici, species tolerant to high temperature. Infections 24 hr old were effectively controlled by the standard hot water treatment, but about 30% of the infections 48 hr old survived and developed into rots.

Keyword(s): Carica papaya L.