As you start to prep for milling often you'll see signs of insect attack. I always say that if in doubt, don't use it. Look closely at the images below and you'll see some black coloration and small but perfectly formed holes in the wood where the adult beetle bored its way out through the sap wood when it reached adulthood. Normally you'll see this just in the sap wood so it's not a major deal to simply cut it away. It's also worth noting that the blackening could be suggestive of some sort of treatment designed to kill the beetles and grubs but either way, you cant use the wood for cosmetic reasons so it's best to cut it away.
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