Influence of bark damage on bluestain development in pine logs
A Uzunovic, J F Webber, D J Dickinson
Mechanized harvesting of conifers can lead to extensive bark damage, with the resulting wounds providing suitable entry points for bluestain fungi that are not associated with bark beetle vectors. However, the amount of bluestain colonisation can vary greatly between the different types of wound. To evaluate the effect of wound type seven different types of wounds were artificially created on freshly felled logs of Corsican pine. These ranged from barely visible punctures, to the removal of large strips of bark, simulating typical harvester damage. The logs were left in the field exposed to natural inocula of wood degrading fungi and assessed after 6 and 12 weeks. Results indicated that surface area of injury was not the best parameter for predicting the rate and extent of staining. Minor disruptions of the bark e.g. crushing and punctures, were sometimes associated with substantial amounts of stain development. Wounds with flaps of loosened but still attached bark were especially susceptible to bluestain colonization, but additional damage to exposed wood surfaces did not result in more stain. Stain development was strongly associated with the edges of wounds where the bark and exposed wood met. Excluding potential bluestain vectors such as bark beetles and weevils by enclosing the logs in netting did not markedly reduce stain, suggesting that micro-arthropods such as mites play an important part in disseminating bluestain fungi to wounds produced during harvesting and log extraction.