A trial was initiated to study the growth of known isolates of sapstain fungi in scots pine (Pinus sylvestris) which had been naturally aged or sterilised by autoclaving or irradiation. Sawlogs cut from commercial thinnings were reduced to billet size and the exposed ends were painted with a bituminous sealant to reduce moisture loss. Some billets were inoculated after autoclaving or gamma-irradiation when freshly felled (time zero) or when nine weeks old. Other non-sterilised billets were inoculated at time zero, three, six and nine weeks. The fungal inocula comprised two isolates each of Leptographium wingfieldii, Ophiostoma piceae, and Sphaeropsis sapinea, which were introduced into the billets below the bark and incubated at 20°C. After two weeks, the bark was removed and the sapwood lesions were measured and recorded photographically. The three species showed different growth characteristics over the trial. 0. piceae had the poorest growth, which increased slightly as the logs were aged. The two isolates of L. wingfieldii differed in colonising ability, but both showed the greatest growth between time zero and three week old logs followed by a decline in growth rate over the rest of the trial. S. sapinea was the most vigorous coloniser, but showed a more or less steady decline in colonising ability as the logs aged. All the fungi exhibited faster rates of growth in freshly felled logs which had been sterilised by autoclaving or irradiation. The lesions exhibited zonation: outer healthy tissue, a central area of stained tissue and an intermediate pale zone. The pathogenic/saprotrophic nature of the inoculated fungi is discussed and related to the condition of the timber.

Download document (1.1 Mb)
free for the members of IRG. Available if purchased.

Purchase this document