Insects Can Take Their Toll

Insects Can Take Their Toll

Then there are insects, plenty of them. Insects recycle dead, down, and wounded trees into fertile soil and plant nutrients. Unfortunately, these little recyclers don't observe "off limit" signs. They'll eat wood destined for your shop (or the wood already there) as well as what loggers leave behind. Here's a roundup of those that make their mark.

Some insects focus only on living trees and green logs Insect species in this category actually number in the thousands. But woodworkers usually never see these culprits, only the results of their activity.

Fly larvae create distinctive marks The dark, thin streaks of varying length running with the grain that you'll often spot on basswood, birch, cherry, maple, and willow boards were made by fly larvae. These pith flecks result from the burrowing of the larvae down through the cambium layer of the living tree toward the ground. The wound heals after the larvae pass, but the tissue turns dark. The pith flecks don't weaken the wood. It only looks bad.

Bark beetles engrave as they go Many insects attack the inner bark of trees (mostly conifers) and freshly cut logs. As they excavate around the trunk, they leave a telltale trail. Visible entrance holes with expelled frass (fecal matter, bark, and wood powder) indicate their work. Because these beetles live on fresh logs and living trees, they perish with the later processing of the wood.

Horntails and others do boring work Some insects bore into trees, logs, and freshly sawn lumber to simply feast. The most common are the pine sawyers and the horntails. The 1/4" to 1" grub holes they leave behind indicate their past presence. You'll find their tracks in hardwoods and softwoods, and in sapwood as well as heartwood. Kiln drying kills their larvae. But if their activity was extensive, the lumber is weakened and its appearance downgraded.