Frost, canker, and dieback of Douglas-fir in the central interior of British Columbia

The relationships between dieback severity of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), growing-season frosts, and invasion by canker pathogens in plantations >10 years old in central British Columbia are described. The coincidence of frosts and dieback events was determined by dissection and by mapping dieback damage in arid around frost pockets. Putative canker pathogens were isolated from bark and fruiting bodies. The timing of significant dieback events coincided with major growing-season frosts, as determined by the formation of frost rings. Damage was most severe in shallow depressions and valley bottoms. Early flushing trees were more severely affected than late flushing trees in two of three plantations. Seven weak canker parasites were isolated from dead Douglas-fir bark. Among these, Sclerophomasemenospora Funk was restricted to tissues killed by frost or other factors, while Leucocytosporakunzei (Fr.:Fr.) Munk and a Sirodothis sp. accounted for about 65% of isolates from recently kille...