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Saturday, 21 January 2017

Red Streaking

Red Streaking Red-streaking discoloration (known as "Rotstreifigkeit" in Germany) is one of the most common and important damage in seasoning logs and sawn lumber, occurring only in conifers (spruce, pine, fir) and recognized as a distinct con-dition in continental Europe. 

The stripe-shaped to spotted yellow to reddish-brown discoloration extends in logs from both their bark-covered faces and from their cut ends (Butin 1995; Baum and Bariska 2002) . Stems that are not debarked show a rather flat discoloration and debarked stems exhibit a streakier staining (v. Pechmann et al. 1967). Causal agents are several white-rot Basidiomycetes, in spruce particularly Stereum sanguinolentum (Kleist and Seehann 1997) and Amylostereum areola-turn. In south Germany, Amylostereum chailettii is common (Zycha and Knopf 1963; v. Pechmann et al. 1967). 

In pine, red streaking is mainly due to Trichap-turn abietinum (Butin 1995). According to Kreisel (1961), S. sanguinolentum and T. abietinum occur often together in stored logs. Red streaking develops if the wood remains in a semi-moist state over a long period, especially in the warmer season (v. Pechmann et al. 1967). The fungi gain access to the wood through the exposed cut ends and bark fissures. 

The mycelium reaches its greatest density in the medullary rays, where the fungus uses the primary storage compounds in the ray parenchyma cells. From there, the discoloration spreads axially deeply in the wood, penetrating the bordered pits and also by thin bore hyphae that perforate the tracheids cell wall (Kleist and Seehann 1997; Kleist 2001). Logs may be stained during overseas shipment, and red streaks producing fungi become again active in rewetted boards due to their ability to dryness resistance. The staining is mainly an oxidative process (Butin 1995). Kleist (2001) stated that the fungi involved excrete the pigments. The moisture optimum of most species lies between 50 and 120% u. 

Red-streaking fungi are slowly growing white-rot fungi, so that initially no serious strength loss is connected with turning red. During longer colonization how-ever an intensive white rot develops with substantial mass and strength loss, so that red streaking damage represents a transition from discoloration to decay (v. Pechmann et al. 1967; Peredo and Inzunza 1990). Secondary infections by brown-rot fungi may occur. Red-streaked wood samples were degraded in the lab test more strongly by brown-rot fungi than controls without pre-infection. From reddish discolored fir wood, 26 Basid-iomycetes (white and brown rot) and numerous blue-stain and mold fungi were isolated (v. Pechmann et al. 1967). From Pinus radiata wood, different molds, blue-stain fungi, Stereum sp. and the white-rot fungi Ganoderma sp., Schizophyllum commune and Trametes versicolor were isolated (Peredo and Inzunza 1990).

 Spruce wood samples from forest dieback sites contained more often A. areolatum and S. sanguinolentum compared to samples from healthy forests (Schmidt et al. 1986). Stereum sanguinolentum Bleeding Stereum small, thin, resupinate to semipileate fruit body, soft-leathery-crusty, bowl-shaped, upper surface: felty, concentrically zonate, yellow-brown, whitish-wavy margin ; bright to grey-brown hymenium blood-red after injury; dimitic (Breitenbach and Kranzlin 1986); amphithallic (Calderoni et al. 2003); apart from the saprobic way of life also parasitic after penetration through wounds and thus the most important species of "wound rot of spruce" (Butin 1995); stacked wood not attacked; genus Stereum with multiple clamps (Kreisel 1969). 

Trichaptum abietinum Fir Polystictus fruit body: annual, resupinate to semipileate and pileate, singly and roofing tile-like; upper surface: white-grey-brown, thin, felty, hirsute, zonate, leathery; pore surface: young net-shaped to porous, old: labyrinthine; young hymenium reddish with angular violet pores, later brown-violet; dimitic (Breitenbach and Kranzlin 1986); tetrapolar heterothallic (Nobles 1965); saprobic on stumps, stored logs and finished wood; severe white rot at high wood moisture; rarely on living trees (Kreisel 1961). 

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