In Britain, mechanised harvesting of conifer forestry crops is now the preferred method of felling where terrain and access allows. However, use of mechanised harvesters can lead to excessive debarking, loosening of the bark and wood splintering with, on average, about a third of the bark removed from the more severely damaged logs. More bark has also been observed to be lost from logs harvested early in the summer (June) than later in the season (August). In an experiment which ran from June October in 1993, mechanically harvested logs with only relatively small amounts of bark damage (mean 12%) were found to be much more susceptible to attack by bluestain fungi than those processed manually, and the damaged areas were associated with extensive bluestain development around the log circumference. The most dramatic staining was produced by Ceratocystis coerulescens and Leptographium wingfieldii. Bark beetles which act as vectors of some bluestain fungi were excluded from the experimental logs, but other insect genera were found to act as casual vectors of the staining fungi. Harvester design and improved skills of harvester operators cannot significantly reduce the potential amount of blue stain degrade as significant reduction of stain only comes with the very low amounts of bark damage (0-10% of circumference) and this is practically unachievable with mechanised methods. Thus rapid delivery of logs for further processing remains the safest way of minimising the opportunity for fungal attack.

Download document (1.5 Mb)
free for the members of IRG. Available if purchased.

Purchase this document