First Report of Septoria Fruit and Leaf Spot, Caused by Septoria cucurbitacearum, on Cucurbita moschata in Illinois. D. M. Eastburn, Department of Plant Pathology, University of Illinois at Urbana-Champaign. Plant Dis. 75:1286. Accepted for publication 29 July 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-1286E.
Septoria fruit and leaf spot was observed on processing pumpkin (Cucurbita moschata (Duchesne) Duchesne ex Poir.) in four commercial fields in central Illinois during the summer of 1990. Leaf spots were small (1-5 mm in diameter), circular to irregular, light tan to brown necrotic areas. Light to dark brown erumpent pycnidia developed in the necrotic tissue of older lesions. Small (1-2 mm in diameter), raised white spots, with dark brown pycnidia forming in the center, developed on the fruit. The size and morphology of pycnidia and conidia produced both on leaf lesions and in vitro on potato-dextrose agar were within the range reported for Septoria cucurbitacearum Sacco Pathogenicity was verified after spray-inoculation of 3-wk-old pumpkin plants (cv. Libby Select) with a suspension of 8 × 103 conidia per milliliter. The leaf lesions that developed on inoculated plants were similar to those observed in the field. Koch's postulates were completed by reisolating S. cucurbitacearum from inoculated plants. Plants were too young to set fruit, so inoculation did not reproduce fruit spots. This is the first report of Septoria fruit and leaf spot on Cucurbita spp. in Illinois and the first report on C. moschata in the United States.