Enhancement of Sphaeropsis sapinea Stem Invasion of Pines by Water Deficits. P. R. Bachi, Department of Plant Pathology, Cook College, New Jersey Agricultural Experiment Station, Rutgers University, New Brunswick 08903. J. L. Peterson, Department of Plant Pathology, Cook College, New Jersey Agricultural Experiment Station, Rutgers University, New Brunswick 08903. Plant Dis. 69:798-799. Accepted for publication 18 February 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-798.

Three-year-old Austrian, Scots, and Japanese black pines growing in a loamy clay soil were inoculated with Sphaeropsis sapinea. Water was withheld for periods sufficient to create soil water potentials of –0.1, –0.6 to –0.8, and –1.2 to –1.5 MPa. Increasingly negative soil water potentials promoted greater linear fungal growth in stems. Scots and Austrian pines were more susceptible to S. sapinea than Japanese black pine, although fungal growth within stems of this normally resistant species was extensive. These findings support field observations of increased infection by S. sapinea on droughted or unhealthy trees.