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Disease Note

Needle Cast of Douglas-Fir Caused by Rhabdocline pseudotsugae subsp. pseudotsugae and Phaeocryptopus gaeumannii in Ontario. D. T. Myren, Great Lakes Forest Research Centre, Sault Ste. Marie, Ontario P6A 5M7. Plant Dis. 68:1099. Accepted for publication 3 July 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-1099a.

Rhabdocline pseudorsugae Syd. subsp. pseudotsugae was identified as the cause of needle cast of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) in a 20-ha Christmas tree plantation near Pontypool, Ontario. The trees were planted in 1971 and were 2 m tall. Phaeocryptopus gaeumannii (Rohde) Petr., Swiss needle cast, was also present in the plantation, and some foliage samples showed both organisms. Defoliation of 25-35% was evident on 5% of the trees. This is believed to be the first report of these fungi in Ontario. P. gaeumanniiwas also found in a 2-ha Douglas-fir Christmas tree plantation near Midland, Ontario; about 50 trees were unmerchantable because of defoliation. Voucher specimens have been deposited with the Biosystematics Research Institute (DAOM 186432) and the Great Lakes Forest Research Centre (SSMF 8350159 and SSMF 8350165).
References:O'Brien, J. G., and Morton, H. L. Plant Dis. 67:661, 1983. Parker, A. K., and Reid, J. Can. J. Bot. 47:1533, 1969.