How do Powderpost beetles primarily damage wood?

Powderpost beetles are known for their distinctive damage to wood, which primarily manifests as a fine powder. This dust is the result of the adult beetles tunneling through wood as larvae, where they feed on the cellulose and starches within the wood. As they burrow, they create exit holes and leave behind this powdery frass, which is often the first indication of an infestation.

The fine powder signifies that the beetles have actively been feeding and boring into the wood, weakening the wooden structure over time. While other options may relate to wood-destroying behaviors of various pests, the hallmark of powderpost beetle activity is indeed the fine powder they produce. This characteristic makes option B the correct choice, as it specifically identifies the primary way these pests cause damage to wood.