Notes from Windward: #68


Blue Stain Fungi

Kerst describes a key Windward fungi

     One of the ways we are able to cut building costs at Windward is to manufacture our own lumber from dead or dying trees on the property. Recently we've been working with a large Ponderosa Pine and many of the boards we've harvested have a blue pattern running along the sapwood of the tree but not penetrating the heartwood (the very core of the tree, usually darker because it stores sugar, dyes and oil).

Sarah cutting deck lumber for Red Box's faux roof

     Walt had seen this pattern in other trees he'd harvested and, correctly believing it was a fungus, asked me to look into what might cause the blue staining. Any fungus that has already established itself in wood has an advantage over other fungi, which presents a problem since we would like to inoculate the chips we make from the dead pine trees we cut down into an edible fungi.

note the blue lines radiating out from the center

     After speaking with my mom, who's worked with the Forest Service since before I came into the picture, I was able to track down that the invading fungus is aptly named "Blue Stain." The presence of blue stain generally does not affect the structural integrity of the wood but will often decrease the value for aesthetic reasons.

      [Walt: which is a good example of value being in the eye of the beholder since at times we've been able to sell blue stained planking for a premium because someone really liked the effect, and it was only available from a custom mill.]

a Mountain Pine Beetle gallery

     On the other hand, some people like the appearance of the stain and intentionally use the patterns created by the fungi. There are several types of fungi which cause blue stain and what we are seeing is likely to be either Ophiostoma clavigerum or Ophiostoma montium, which are both associated with pine beetle attacks. It's likely that our trees have been attacked by either the mountain pine beetle or the western pine beetles, both common in the Pacific Northwest, and inspection of the inner bark reveals larva galleries more similar to that of the mountain pine beetle (straight and mostly vertical rather than the winding paths left by western pine beetles).

a Western Pine Beetle gallery

     Pine beetle infestations are becoming increasing widespread due to several factors. Pine beetles are most susceptible to extreme temperatures, especially cold. As our winters are becoming more mild and Nature's beetle-control mechanism ceases to exist. Also effective in managing beetle populations is the practice of controlled burning, which becomes more difficult to do as humans continue to build homes close to potentially vulnerable forested areas.

     The mountain pine beetle attacks pines, preferring larger diameter trees, and bores into the phloem, or inner bark, where it feeds on the tree's nutrients and lays eggs. Egg laying females initiate the attack but then give off pheromones that attract large numbers of males, which can eventually overwhelm the tree. The tree responds to the initial infestation by increasing it's resin output in an effort to plug up the bore holes, which is why you can often see excess tree resin coming out of the trunk of an infected tree.

Kerst points out a beetle entry hole amidst the resin

     However, the resin response is blocked by blue stain fungi which is introduced by the bark beetles, quite the symbiotic relationship. The blue stain fungi spreads from the phloem through the sapwood, which acts as the conduit for water and nutrients from the roots up to the leaves where it's converted to resin. Resin proceeds to flow back down the tree via the phloem. Once the fungi is well established, the water and nutrients are either blocked or consumed before reaching the leaves, resulting in resin response failure. Eventually the combination of blue stain fungi and bark beetles kills the tree and the following year the beetles fly off to other trees, carrying with them their faithful fungus.

Notes From Windward - Index - Vol. 68