Spore dispersal and infection of lodgepole pine by Dothistroma septosporum in northwest British Columbia.

Spore dispersal and infection by Dothistroma septosporum which has severely attacked lodgepole pine plantations in northwest British Columbia were studied. Spore abundance was assessed at different distances and heights from single juvenile tree inoculum sources and microclimatic factors were recorded during two consecutive years. One- year-old lodgepole pine seedlings were exposed to natural conditions at the study sites for inoculation. Conidia were assessed from spore traps from June to September in 2009 and were present in the samples whenever rain fell, with a peak in July. It was rare to detect spores more than 2 m away from inoculum sources. The timing and number of conidia dispersed were strongly tied to the climatic variables, particularly rainfall. Infection of the seedlings by the fungus was strongly influenced by the exposure periods, number of spores and high relative humidity. The results suggest increasing the planting distances between susceptible tree species through mixed species plantations and promoting dry conditions within pine plantations may be valuable strategies to reduce the spread of the disease and manage lodgepole pine plantations in the area. --P. ii.