Development of blue stain in mechanically harvested Scots pine (Pinus sylvestris) logs during storage

Abstract

Blue stain is a type of discoloration that considerably lowers the aesthetic qualities of wood. During harvesting, fungal inoculum finds its way into the wood through places of cutting, delimbing, and damage to the tree stem. The development of peripheral blue stain in the logs of Scots pine (Pinus sylvestris L.) due to damage by a harvester head was investigated, using logs felled and delimbed with a chainsaw as reference. The development of blue stain was related to the age class of the stand, the date of felling, and the microclimatic conditions of the wood storage place. The mean surface area of blue stain in logs produced with the harvester was almost 35 cm2, approximately 30% larger than that of the reference logs. In stands of the fourth age class (diameter at breast height 32 cm), the surface of blue stain was more than two times larger than that of stands of the third age class (diameter at breast height 24 cm). The mean area of blue stain in wood stored after spring felling (19.3 cm2) was about 50% of that after summer felling (38.2 cm2). In particular, the development of blue stain in logs obtained with a harvester was visible between weeks 6 and 9 after spring felling and between weeks 3 and 6 after summer felling. For both felling dates, the range of blue stain depended less on air temperature around the wood stack and depended more on the duration of storage.

Blue‐stain fungi isolated from freshly felled Scots pine logs in Poland, including Leptographium sosnaicola sp. nov

“…Melville) using a mechanised harvesting machine are much more susceptible to colonization by blue‐stain fungi than chainsaw‐processed logs and the study was done in absence of obvious bark beetle attack which would normally bring blue‐stain fungi associated with the beetle (Uzunović et al., 1999a). A similar pattern was recently found for Scots pine logs in Poland (Szewczyk et al., 2020). In addition, in the Polish investigation, the blue‐stain area developed in sapwood stored after spring felling was significantly less than that after summer felling.…”

“…The mean area of blue‐stain in wood stored after spring felling was significantly lower than that in wood stored after summer felling. In addition, the development of blue‐stain in logs was visible between the 6th and 9th weeks after spring felling and between the 3rd and 6th weeks after summer felling (Szewczyk et al., 2020). Most likely, favourable microclimatic conditions, especially air temperature, could profoundly affect the development of blue‐stain fungi in sapwood.…”

“…The methodological details for the estimate of blue‐stain area have been described previously by Szewczyk et al. (2020).…”

“…During the entire storage period, the microclimate was monitored in terms of air temperature and relative humidity using a HOBO Pro v2 U23-001 temperature and relative humidity data logger (Onset Computer Corporation, Bourne, Mass., USA) located on the support of the wood stack. For more detailed information on microclimatic parameters in the vicinity of wood, stacks are provided by Szewczyk et al (2020). During the experiments, the logs felled in July were occasionally colonized by the bark beetle Ips sexdentatus (Born.…”

“…In each season's sampling, samples of wood were taken four times: 3, 6, 9 and 12 weeks after tree felling following the procedures described by Uzunović et al (1999a). From each laying log, 3-cm thick discs with intact bark were cut off with a chainsaw (two discs per measurement period: one at the butt end and the other at the top end) as described by Szewczyk et al (2020). This method allows examination of blue-stain that progresses from wounds at the log surface (Beal et al, 2010).…”