Development of fungal stain in logs of three Canadian softwoods

Freshly felled wood is susceptible to fungal stain, and the severity of the infection may vary with various environmental and storage conditions. Information on how long it takes for stain to develop in logs would be very useful to help sawmills effectively reduce losses from stain through proper management. In this study, we conducted a systematic survey at three selected sawmills in eastern Canada to study fungal stain development in logs. The work was done through the summer of 1997. Freshly felled logs of jack pine (Pinus banksiana ), black spruce (Picea mariana ), and balsam fir (Abies balsamea) were closely stacked and left for 1 month in an undisturbed part of sawmill yards. The logs were then sampled destructively by cutting five 2- to 3-cm discs along the length of each log. Stain area and maximal radial stain penetration were measured in each disc after the isolation of causal microorganisms. The results showed that a period of 30 days of log storage during the summer was enough for significant stain development under test conditions. Among the three wood species used in the experiment, jack pine was the most susceptible, followed by black spruce (except at one location) and balsam fir. There was substantial variation in stain development in different locations as well as among individual logs. The majority of fungi isolated from these logs were staining fungi. Decay fungi were rarely encountered but various molds were frequently associated with stained wood.

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