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Disease Note.

First Report of Endive and Escarole as Hosts of Sclerotinia minor. S. T. Koike, University of California Cooperative Extension, Salinas 93901. K. V. Subbarao, Department of Plant Pathology, University of California, Davis and located at U. S. Agricultural Research Station, Salinas 93905. Plant Dis. 79:642. Accepted for publication 17 May 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0642E.

In 1994, endive (Cichorium endivia L. 'Broadleaf Batavian') and lettuce (Lactuca sativa L. 'Salinas') were planted in a field trial near Salinas, Calif. Plants were thinned 4 weeks after emergence. One week later, plants were inoculated with a Sclerotinia minor Jagger isolate from lettuce. Inocula consisted of a mixture of sclerotia and mycelia-infested oat seed; the mixture was placed on top of the soil 1 cm away from the plant crowns. As plants approached maturity, 80% of the lettuce plants collapsed and died, and 19% of the endive plants developed chlorosis and necrosis of lower leaves with localized necrosis of crown tissue. The small sclerotia of S. minor formed on these diseased tissues. Necrotic crown tissues were plated on acidified potato-dextrose agar, and S. minor was recovered and identified from colonies that developed after 4 days at 23 to 24C. Pathogenicity of the S. minor isolated from endive was determined by transplanting into sterilized sand 20 4-week-old plants each of endive (cv. Ruffec), escarole (Cichorium endivia L. 'Full Heart'), and lettuce (cv. Alpha). Three or four sclerotia, taken from sterilized-potato-slice culture (1), were placed in the sand 0.5 cm deep and 0.5 cm from the plants. Ten control plants of each cultivar were grown similarly, but without soil infestation. After 3 weeks in a greenhouse at 21 to 23C, the inoculated plants wilted and collapsed. Sclerotinia minor was reisolaled from necrotic crown and stem tissues. Controls showed no symptoms. The test was repeated with identical results. This is the first report of endive and escarole as hosts of S. minor. While 19% of the field-planted endive developed disease symptoms. S. minor sclerotia formed on the lower senescent leaves of virtually all of the endive plants in the trial. Sclerotinia minor on endive and escarole may contribute inoculum that could increase lettuce drop on the lettuce crops in the Salinas Valley of California.

Reference: (1) C. L. Patterson and R. G. Grogan. Plant Dis. 72:1046, 1988.