Which statement does NOT accurately describe bark beetle damage?

The statement that larval tunnels are free of frass is not an accurate description of bark beetle damage. In fact, frass, which is a mixture of wood shavings and insect excrement, is typically present in the tunnels created by bark beetle larvae. This frass can often be seen accumulating at the entrance of the tunnels or falling from the tree, indicating active infestation.

In contrast, the other statements provide accurate characterizations of bark beetle damage. The wood that has been affected by bark beetles is usually stained due to the disruption of the tree's ability to transport nutrients and water. This staining results from the tree's response to the infestation and the introduction of pathogens. Additionally, bark beetle activity creates visible exit holes as adult beetles emerge from the wood, and severe infestations can indeed lead to tree mortality due to the extensive damage caused by the larvae feeding under the bark and disrupting the tree’s vascular system.