The Second or Third Most Interesting Blog Post You Will Ever Read on Mold


Already you’re most likely dying to see the number one most interesting post on mold, but I’m riding a wave of optimism that has me believing that this brief, albeit interesting article won’t be the peak of my career in the mold world.

To set the stage, there is a situation that our company experiences frequently involving a fungal growth called Blue Stain or Sap Stain. This fungal problem is a common problem in many lumber yards, and once the lumber is used in construction, it is consequently a problem in many homes and businesses. While this fungal growth is commonly seen, its exciting history of riding flying beetles and combatting other fungal species are far less widely known.

Some examples of what this looks like in finished wood can be found here:

Genus Ophiostoma

Although many different kinds of fungal growth can occur in lumber yards that can then be used in the construction process, today we are primarily looking at fungal species in the genus Ophiostoma which are most commonly known for causing the blue sap stain.

Sap stain makes its appearance quickly after a tree’s natural defense mechanisms have been weakened. This can be freshly cut lumber, trees knocked down in windstorms, and other similar instances. It is called sap stain because it only affects sap wood; the soft layers of new wood beneath the bark of the tree. Blue Stain, as it is also commonly called, is because of the dark blue staining it leaves behind.

Ophiostoma spores are wet and slimy, making them difficult to be spread by typical fungal transportation such as wind. Although they can be transported by water droplets, this usually does not take the spores very far. What makes ophiostoma interesting (as promised) is their spores’ utilization of pine beetles to get to new food sources.

Symbiosis…between beetles and microscopic fungi?

Pine beetles tend to find weak and unhealthy trees to infect. The natural defenses of the tree are less affective in these situations and allow for the beetles to make easy work of feeding on the tree. However, to make this process even more easy, a symbiotic relationship is formed between the fungus and the beetles. The spores hitch rides on the beetles as they fly from tree to tree, and once deposited on a new food source, help contribute to weakening the trees’ defenses.1

Imagine now, fungal spores instead of being limited to the whims of slow moving water droplets for their primary transport between food sources, now hitching rides on swift moving flying beetles going directly to new and exciting places. The extent of this that is premeditated by the beetles and fungal spores is probably minimal; however, the imagery of spores riding beetles into battle against trees is entertaining at the very least.

The ophiostoma fungus itself does not typically harm the structural integrity of the wood. Instead of feeding on cellulose and lignin like many decaying fungi, ophiostoma fungi feed on the nutrients within the cells (sugars, starches, proteins). The blue or dark staining present in the lumber occurs because of the fungi synthesizing melanin in their hyphae.1 The pigment remains in the hyphae root structures in the wood and follows the fungus wherever it grows.

Because it does not harm the structural integrity of the wood, the blue stain is primarily a cosmetic defect. Consumers typically like to see an unblemished wood product and thus lumber yards are left vigorously combatting the fungal growth.

Treating Blue Stain, and fighting fungus with fungus

Depending on the depth of the pigment containing hyphae, some staining can be removed by planing or sanding until the hyphae structures are removed from the wood. This can be time consuming but can return the wood to its more natural looking condition and reestablish its value to the consumer.

Anti-microbial chemicals are also often used but due to environmental effects, other methods are being developed. One of the most promising methods is the isolation of albino strains of ophiostoma. These strains do not synthesize melanin and thus do not leave the discoloration in their hyphae structure.2

These albino strains are purposely introduced to freshly cut lumber as a preemptive strike against other strains of ophiostoma that are likely to show up. By giving the albino strains a head start on colonization, it prevents staining from other fungi from occurring.

More than Meets the Eye

So although the effects of blue stain are visible in many places, the fungal story that surrounds it is almost entirely unknown. Beetle riding spores fought with preemptive colonization by albino strains? Sometimes nature is a living fantasy story right in front of us.







Leave a comment