Susceptibility of harvested softwoods to infection by sap-staining fungi

IRG/WP 02-10435

E J Young, R A Eaton, J F Webber

In the UK a field study programme was carried out to compare the susceptibility of softwood timber from five different commercially important tree species to infection by sap-stain fungi. Logs cut from freshly felled Scots pine (Pinus sylvestris), Lodgepole pine (P. contorta var. latifolia), Sitka spruce (Picea sitchensis), Norway spruce (P. abies) and Japanese larch (Larix leptolepis) were exposed for 4 months (April to August 2001). Samples were taken 5cm and 50cm from the end of the logs after four weeks, eight weeks and 16 weeks. The percentage area of sap-stain was then measured in all samples, and isolations taken from the stained wood to identify the fungi causing discolouration. Sap-stain was markedly greater in the two pine species compared with the three other species. We concluded that the susceptibility of the tested tree species was as follows: most susceptible Lodgepole pine @ Scots pine > Norway spruce > Japanese larch > Sitka spruce. In the 5cm samples assessed after four months this equated to a mean stain area of 59%, 61%, 10%, 4% and < 1% in the respective species. Moisture content of the logs was also measured. With an increase in exposure time moisture loss from the logs was progressive. The two species of pine showed the least loss of moisture overall, and moisture loss was less in the 50cm samples than the 5cm samples taken from the log ends. The exception to this was Lodgepole pine. Several factors may influence the susceptibility of particular tree species to sap-stain infection including moisture content, nutrient and extractive composition and volatile compounds within the timber. The effect of log ageing may also affect sap-stain susceptibility. The importance of some of these factors and the composition of the sap-stain community from the five timber species will be investigated in further work.


Keywords: Sap-staining fungi, susceptibility, moisture content, softwoods.

Conference: 02-05-12/17 Cardiff, Wales, UK


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