WHITE-ROT AND MANGANESE DEPOSITION IN TNBTO-AAC PRESERVATIVE TREATED PINE STAKES FROM FIELD-TESTS

A pine test stake previously impregnated in 1978 with 12.0 kg/m(3) loa ding of a TnBTO-AAC formulation and set out under field test condition s in the south of Sweden failed in the summer of 1996 with decay rate of Class 4 according to EN 252. Visual and microscopic examination of the test stake showed the outer 1-2 mm to be degraded by soft rot cavi ty forming fungi whereas internal attack throughout the groundline reg ion and below was by simultaneous white rot characterized by cell wall thinning, and pronounced bore hole formation. Observations showed the visual presence of very large numbers of characteristic brownish-blac k flecks associated with the white rotted wood. These flecks were char acterized by transmission electron microscopy (TEM) in conjunction wit h x-ray microanalysis and were found comprised primarily of manganese possibly as MnO2. Observations further showed gross manganese penetrat ion into partially degraded tracheid wall layers and middle lamella re gions and its association with extracellular fungal slime in the wood cell lumina.