The mode of infection and early stages of colonization of pines by Gremmeniella abietina

Gremmeniella abietinainfects shoots of red and Scots pines through stomata on bracts that subtend short shoots. The germ tube penetrates between guard cells and sparsely colonizes bract tissue by late summer or fall. Only after about late January or early February of the following year does the fungus extend from the bract and begin colonization of the short shoot and surrounding cortical tissue.