Association of Mortality of Recently Planted Seedlings and Established Saplings in Red Pine Plantations with Sphaeropsis Collar Rot. Glen R. Stanosz, Assistant Professor, Departments of Plant Pathology and Forestry, University of Wisconsin-Madison, Madison 53706. Jane Cummings Carlson, Wisconsin Department of Natural Resources, 3911 Fish Hatchery Road, Fitchburg 53711. Plant Dis. 80:750-753. Accepted for publication 25 March 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0750.

Established saplings and recently planted seedlings frequently died during 1991 and 1992, respectively, in red pine (Pinus resinosa) plantations in Wisconsin. Mortality of seedlings in 12 plantations ranged from 14 to 95%. Mortality’of saplings in 16 plantations ranged from 0 to 30%. Symptoms included blackened cortical tissue and dark staining of the underlying xylem in the lower stems and root collars. Pycnidia of Sphaeropsis sapinea were observed in these areas on 17 to 97% of dead seedlings. Pycnidia of the pathogen were observed on the lower stems or root collars of 67 to 87% of dead saplings examined in four plantations. These epidemics appear to be related to substantial rainfall deficits in each year, compared to 30-year averages. These observations comprise the first association of Sphaeropsis collar rot with high frequencies of red pine mortality in these situations.

Keyword(s): Diplodia pinea, drought, water stress