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Disease Note.

First Report of Geastrumia polystigmalis on Apple and Common Blackberry in North America. E. M. Johnson, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616. T. B. Sutton, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616. Plant Dis. 78:1219. Accepted for publication 3 October 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-1219A.

While examining common blackberry stems (Rubus argutus Link) and apple fruit (Malus? domestica Borkh.) in North Carolina for fungal colonies, thalli and pycnidia atypical of the apple sooty blotch pathogen Gloeodes pomigena (Schwein.) Colby were observed. Specimens on brambles were collected in April and May 1993; specimens on apples were collected in June 1993. Whole mount, squash, and cross sections were made for histological evaluation of morphological characteristics. Subglobose pycnidia 50-100 µm in diameter with ragged tears in the apex were observed. When a droplet of deionized water was placed on the colony, pycnidia swelled and fusiform conidial arms with 7-9 septa were teased out from the torn opening. The fungus was identified as Geastrumia polystigmatis Batista & M. L. Farr (I) by B. C. Sutton (International Mycological Institute, [IMI]). Colonies characteristic of G. polystigmatis were observed on apple fruit during the summer of 1993 but pycnidia were rarely found on them. However, a small barren circular area within the thallus remained as evidence of the prior presence of pycnidia. The fungus was readily cultured on potato-dextrose agar. This is the first report of G. polystigmatis in North America. This fungus was previously reported in Tanzania on Hymenocardia acida Tul. and Costus afera Ker. and in the Dominican Republic on Andira jamaicensis Urb. Specimens were deposited in the herbarium of the IMI (IMI 358517 and 358518).

Reference: (1) K. A. Pirozynski. Mycologia 63:897, 1971.