Seasonal Response of Pinus radiata in South Africa to Artificial Inoculation with Sphaeropsis sapinea. W. J. Swart, Department of Plant Pathology, University of the Orange Free State, Bloemfontein 9300, South Africa. M. J. Wingfield, Department of Microbiology and Biochemistry, University of the Orange Free State, Bloemfontein 9300, South Africa. Plant Dis. 75:1031-1033. Accepted for publication 28 March 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-1031.

Trials were conducted in the winter rainfall region of South Africa to determine the effect of season on the rates of colonization of pine tissue by three isolates of Sphaeropsis sapinea. Four-year-old Pinus radiata trees were inoculated during fall and spring in 1986 and 1987. In both years, cambial lesions caused by S. sapinea on trees inoculated in spring were significantly longer than those on trees inoculated in fall. There was a significant interaction (P < 0.01) between seasons and isolates. Thus, season can influence the outcome of infection by S. sapinea. Management operations such as pruning or felling may be timed to avoid making wounds (loci of infection and colonization) before or during the summer dry seasons.