Conidial dispersal of Sphaeropsis sapinea in three climatic regions of South Africa.
Conidia of S. sapinea [Diplodia pinea] 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 max. monthly temp. and monthly spore count for any of the regions. Although conidial dispersal was strongly related to the occurrence of rainfall, peak conidial dispersal in the 3 regions succeeded peak rainfall by up to 16 weeks. Max. conidial production occurred in spring (Oct.) in the winter rainfall region, in early summer (Dec.) in the constant rainfall region, and in late summer (Feb.) in the summer rainfall region. It is suggested that, in all 3 climatic regions, winter is the most desirable time for management operations such as pruning that favour infection by D. pinea.