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Unfinished interior wood members in wooden cultural heritages undergo severe discoloration by fungal attack during the summer rainy season. The prevention of fungal discoloration is crucial in the conservation of wooden cultural heritages. It is important to investigate discoloration properties of major mold and stain fungi under different relative humidity conditions to prevent discoloration damage. Among the 54 ascomycetes isolated from wooden cultural heritages in Korea, Aureobasidium pullulans, Cladosporium cladosporioides, Coniochaeta velutina, and Graphiopsis chlorocephala were selected as test fungi because of their particularly strong discoloration intensity on wood. For each fungal species, the minimum relative humidity and exposure period for discoloration were investigated. It was found that A. pullulans and Cl. cladosporioides started to grow and discolor at 75% relative humidity within 3 weeks to 4 weeks, and Co. velutina and G. chlorocephala grew and discolored at relative humidity values greater than 95%. Therefore, the prevention of fungal discoloration of interior wood members by A. pullulans and Cl. cladosporioides for the proper conservation of wooden cultural heritages can be achieved by maintaining an indoor relative humidity of 75% or less during the summer rainy season.

Typical symptoms of rubberwood canker found in East Kalimantan, Indonesia, differ from those of conventional rubberwood peach canker. Rubberwood canker showed a conspicuous longitudinal canker with exposed xylem that was discolored and decayed. Bark wounds, resulting from regular tapping, were enclosed within the xylem, and the tissues had become integrated. The characteristics of abnormal and decayed xylem in this rubberwood canker were analyzed by light microscopy and scanning electron microscopy. Xylem in the vicinity of the enclosed bark contained fewer vessels of smaller diameter and shorter length, and significantly wider rays compared with normal xylem. Around the wide growth zones of the canker, axial cells were disoriented and warped toward the canker zones. In view of the separation among cells, and the concentric degradation of the cell walls starting from the lumen surfaces, decayed xylem appeared to be caused mainly by white-rot fungal attack.

The potential of termite (Coptotermes formosanus Shiraki) and fungal attacks [Fomitopsis palustris (Berkeley et Curtis) Murrill (FFPRI 0507) and Trametes versicolor (L. ex Fr.) Quel (FFPRI 1030)] against moso bamboo (Phyllostachys pubescens Mazel) were evaluated with regard to the seasonal and height-dependent changes of the free glucose and starch contents, which were measured by a newly developed method. The free glucose contents were generally lower in autumn and winter than in spring and summer, whereas the lowest starch contents were obtained in August, and the contents increased almost linearly up to February and March. In terms of the height-dependent fluctuation, the free glucose contents tended to decrease as the sampling heights increased. There was no special correlation between the free glucose or starch contents and the consumption by termites, even though higher mortalities were obtained in the bamboo-fed termites than in the wood-fed termites. However, a positive correlation between the free glucose contents and mass losses of the samples at 4-m and 8-m heights from the bottom by the decay fungi was observed. For starch, no influence on fungal attack was found.

The amount of boron contained in the xylem of Japanese persimmon (Diospyros kaki Thunb.) and ebony (Diospyros ebenum Koen) was determined by inductively coupled plasma (ICP) emission spectrometry and a modified curcumin—acetic acid method. The boron content was compared between the heartwood and sapwood of ebony as well as between a blackened portion (“kurogaki”) and normal portion of Japanese persimmon. The kurogaki contained a higher level of boron than the normal portion of the same individual, although the boron content varied among individuals. Moreover, the boron content of the heartwood of ebony was much higher than that of the sapwood. These results suggest the participation of boron in the blackening of Japanese persimmon. Because both kurogaki and heartwood of ebony are durable to fungal attack, the blackening of Diospyros genus appears to be related to the formation of defensive substances in which boron seems to take part. The convenient curcumin—acetic acid method is an alternative to the ICP method with comparable accuracy.

The heartwood of the Japanese persimmon tree (Diospyros kaki) becomes black on rare occasions and has been highly esteemed as a substitute for ebony. We attempted to clarify how the physical, mechanical, chemical, and biodegradation properties differ between sapwood and blackened heartwood. The specific gravity, equilibrium moisture content, modulus of rupture, and modulus of elasticity in the blackened heartwood were higher, and the loss tangent was lower, than those in sapwood. Furthermore, the blackened portion was more resistant to fungal and termite attacks. A section of heartwood was dark-brown, and the specific gravity and mechanical properties of this portion were slightly lower than those in sapwood. The dark-brown portion was speculated to be a sign or interrupted state of fungal attack. The blackening substance was bound tightly to cell wall components and could not be extracted with any of the organic solvents used. The findings of trace element analysis using inductively coupled plasma-mass spectrometry showed that the boron content was markedly high in the blackened portion. The findings obtained here suggest a role of boron in the antifungal properties and the blackening phenomenon of Japanese persimmon.