Issue link: http://palletcentral.uberflip.com/i/1115386
palletcentral.com PalletCentral • March-April 2019 23 Bluestain Bluestain is not mold; it is a common cause for the discoloration of lumber. Certain dark- colored microscopic fungi cause a bluish or grayish discoloration in the sapwood of the tree. Not all bluestains are blue. Other stain shades can be blue, bluish black, gray, brown, red, yellow, orange, or purple. Bluestain has no effect on the performance and strength of lumber. It can be used for exactly the same purpose as non-stained lumber. Bluestain poses no health risk, and is safe to handle. (reference sidebar for more on bluestain). Surface bluestain is caused by similar bluestain fungi that invade sapwood after the logs have been processed through a sawmill into lumber. They don't penetrate the wood deeply but cause discoloration in the wood's surface that's sometimes confused with decay mold. Bluestain does not destroy the wood cell's wall to force decay. As with surface grown molds, these fungi can be removed from the surface of the wood by planing it. Deep bluestain fungi are typically from trees that grow deep into sapwood causing dark blue or gray discoloration. The fungi attach themselves to insects that attack trees or logs, especially bark and ambrosia beetles, such as the mountain pine beetle. Any tree or log that is attacked by beetles is likely bluestained. Thus, if a tree has its bark intact, then it won't be impacted. Trees and logs with damaged bark are also susceptible to be colonized by bluestain fungi. Once the bluestained log is converted to lumber, it shows long blue or gray streaks of color, hence the name "bluestain." This stain appears in a radial pattern from the center to the outside of the tree. Bluestain fungi does not destroy the wood cell's wall. Its impact on the strength of the wood is minimal and it will stop growing once the wood has been heat treated or it has a 19% or less moisture content. Because deep bluestain infiltrates the tree via insects prior to it being felled or as a log in inventory, not much can be done to prevent it from discoloring the wood. Some industries may try to chemically bleach impacted lumber but this is not a widespread industry practice. PC