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Seasonal Availability of Phaeocryptopus gaeumannii Ascospores and Conditions That Influence Their Release. E. Michaels, Western Washington Research and Extension Center, Washington State University, Puyallup 98371. G. A. Chastagner, Western Washington Research and Extension Center, Washington State University, Puyallup 98371. Plant Dis. 68:942-944. Accepted for publication 16 June 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-942.

Ascospores of Phaeocryptopus gaeumannii were released from pseudothecia on moistened needles from April through September, with maximum numbers released during June and July. Pseudothecia on 1-yr-old needles released 10 times more ascospores than did those on 2-yr-old needles. Moistened pseudothecia released 75% of available ascospores within 20 min and all within 4 hr. Ascospores were released at 530 C, with maximum release at 20 C. Compared with darkness, ultraviolet or fluorescent light sources enhanced ascospore release.