Which stage of the powderpost beetle life cycle is most destructive to wood?

The larvae stage of the powderpost beetle is the most destructive to wood because it is during this phase that the beetles feed and develop. Once the eggs are laid in or on the wood, they hatch into larvae, which then burrow into the wood, consuming it for nourishment. The larvae can create extensive galleries within the wood as they eat through it, causing significant structural damage.

While the other stages each play a role in the life cycle, they do not cause direct damage to wood. Eggs do not have the capability to damage wood since they are only in the initial stage of development. The pupal stage occurs after the larvae have completed their feeding and before they emerge as adults, and during this stage, there is no active feeding or damage being done. Adults, while they can create exit holes and lay eggs, do not feed on the wood themselves, so their impact in terms of wood damage is much less significant compared to the larvae.