Conidial Dispersal of Sphaeropsis sapinea in Three Climatic Regions of South Africa. W. J. Swart, Plant Protection Research Institute, Private Bag X5017, Stellenbosch 7600, South Africa. M. J. Wingfield, and P. S. Knox-Davies. Plant Protection Research Institute, Private Bag X5017, Stellenbosch 7600, South Africa, and Department of Plant Pathology, University of Stellenbosch, Stellenbosch 7600, South Africa. Plant Dis. 71:1038-1040. Accepted for publication 7 May 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-1038.

Conidia of Sphaeropsis sapinea were trapped in pine plantations in regions of South Africa with summer, winter, and constant rainfall. Spore traps, made from microscope slides coated with petroleum jelly, were collected weekly over a year. Vertical slides trapped conidia deposited by impaction and were more efficient than horizontal slides that trapped those deposited by sedimentation. There was no direct relationship between mean maximum monthly temperature and monthly spore count for any of the regions. Although dispersal of S. sapinea conidia was strongly related to the occurrence of rainfall, peak conidial dispersal in the three regions succeeded peak rainfall by up to 16 wk. Maximum conidial production occurred in spring (October) in the winter rainfall region, in early summer (December) in the constant rainfall region, and in late summer (February) in the summer rainfall region. These results suggest that, in all three climatic regions, winter is the most desirable time for management operations such as pruning that favor infection by S. sapinea.