Agreed - the grain looks A LOT like White Oak, but I don't think powder post beetles or other insects attack White Oak - maybe someone smarter will weigh in?Had you asked "What type of wood is this?", I would have said: "White oak". However, I have never had any experience with chestnut, so can't rule it out.
Appears to be White Oak. Typically very resistant to insects...that one piece looks like it laid on the ground for a while at some point which would have made it prone to insect attack.