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Disease Note

Meria laricis Found on European Larch in Ontario. D. T. Myren, Department of the Environment, Canadian Forestry Service, Great Lakes Forest Research Centre, P. O. Box 490, Sault Ste. Marie, Ontario P6A 5M7. Plant Disease 68:732, 1984. Accepted for publication 7 May 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-732e.

Meria laricis Vuill. was identified as the cause of a needle cast of European larch (Larix decidua Mill.) in a 28-ha plantation of mixed confiers near Chatsworth, Ontario.  The affected trees averaged 12 m in height and 19 cm DBH.  Defoliation ranged from 10 to 30%, with almost total defoliation noted on six trees 3 m high.  M. laricis was previously known in North America only on western larch (L. occidentalis Nutt.) in the states of Washington, Idaho, and Montana and in the Canadian provinces of British Columbia and Alberta.  The Ontario collection is the first North American record of M. laricis on European larch.  M. laricis causes a serious disease of European larch in nurseries in Europe and therefore is a potential problem for nurseries in Ontario producing European larch and larch hybrids.  Voucher specimens have been deposited at the Biosystematics Research Institute in Ottawa (DAOM 188195) and at the Great Lakes Forest Research Centre (SSMF 8350755 and 8359021).