Impact of decay and blue stain causing fungi on the structural integrity of wood
C Brischke, C Welzbacher, T Huckfeldt, F Schuh
The potential influence of diverse decay patterns caused by different brown rot provoking basidiomycetes on the structural integrity of wood was investigated. Additionally the potential impact of blue stain on the structural integrity was examined. Therefore decayed Norway spruce (Picea abies Karst.) specimens representing a wide range of mass loss, caused by four different brown-rot fungi and one white-rot fungus, were applied to a high-energy multiple impact (HEMI) -test series. The relationship between the resistance to impact milling (RIM) and the mass loss by fungal decay could be subdivided in three areas: 1. Prior to measurable mass loss a strength reduction was detectable due to the depolymerisation of wood cell wall components. 2. Between 0 and 25-30% mass loss RIM decreased with increasing mass loss. 3. Above 30% mass loss RIM increased again due to gluing effects of the fungal mycelium. The influence of the different brown rot fungi on the structural integrity of the wood differed slightly, but partly significantly. According to preliminary results blue stain caused by Aureobasidium pullulans and Sydowia polyspora was found to have no significant impact on RIM.
Keywords: brown rot, early decay detection, HEMI-test, resistance to impact milling, strength loss, testing, white rot, blue stain