What would cause a white powdery substance to shed from wood near ceiling inside a cabin ? I can see no sign of insects or holes in the wood Could it be mold or decay from moisture and would a dehumidifier help resolve the problem ?
It sounds like it is frass from Powder Post Beetle. The holes are tiny. I doubt that it is mold but you may want to have a mold remediation company look at it to be sure.
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