What is bluestain?
This is a common blue-toned wood discolouration in softwoods, especially pines. The stain is caused by a type of harmless fungus. Bluestain occurs only in the sapwood, which is the outer part of the tree, closest to the bark – this is why a piece of lumber may be stained only in a very distinct section of the wood. Bluestain fungi are usually carried by forest insects, mainly bark beetles. These are common in the forest and in areas where logs are stored. When the insects land on logs that have bark partially removed, or when they attack standing trees or logs with bark still on, the fungi can germinate and grow into the sapwood. While the fungi penetrate deep into the sapwood, the bark beetles do not. In addition, the beetles are no longer present in finished products as the bark is removed during processing. Some people mistakenly confuse bluestain with mold. Under the microscope you would see that the stain is caused by dark coloured threads of fungus growing in part of the wood tis
