Disease Note

Mycosphaerella pini on Scots Pine in Ontario. D. T. Myren, Forestry Canada, Ontario Region, Box 490, Sault Ste. Marie, Ontario, P6A 5M7, Canada. Plant Dis. 75:644. Accepted for publication 31 January 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0644E.

Red band needle blight, caused by Mycosphaerella pini Rostr. in Munk (anamorph Dothistroma septospora (Doroguine) Morelet var. septospora), was identified as the cause of needle mortality on Scots pine (Pinus sylvestris L.) in a northern Ontario Christmas tree plantation. Trees in the 2-ha plantation, just north of Blind River, averaged 2 m in height. Damage was confined to the lower three branch whorls, which were sheltered by tall grasses and ferns. Of 100 trees sampled, 43 were infected, with an average of 2.4% foliar damage. On the affected whorls, damage levels exceeded 80%. The disease was first reported in a Christmas tree lot, where customer complaints forced the owner to remove the bottom 30 cm of affected trees, at an estimated cost of $5 (Canadian) per affected tree. This is the first report of M. pini on Scots pine in Ontario and is a significant northern extension of the geographic range of the fungus in the province. Previous collections of M. pini in Ontario were on Austrian pine (P. nigra Arnold) in the Toronto and Simcoe areas. Identification of M. pini was confirmed by M. Corlett of the Biosystematics Research Centre (BRC) in Ottawa. Voucher specimens are on deposit at BRC (DAOM 198221) and Forestry Canada, Ontario Region, (SSMF 87-5-1438).