Firewood Insects

Asked October 31, 2016, 8:49 AM EDT

We have a combination of ash and cherry for our indoor fireplace. The wood is intermingled in the stack. Yesterday we were moving the stack from out back to behind the house for easier access. We noticed that the ash had a lot of what appeared to be sawdust. Although it is much finer than one would expect sawdust to be, in fact, it's more garlic or onion powder. There are also very small black specs withing the dust, and are only on the ash. So what might this be, and is there any danger of bringing some of this wood inside the garage for storage? Is the dust harmful if inhaled?

Livingston County Michigan insect issues

1 Response

It’s hard to make a definitive identification but from your description of the “sawdust’ like material coincides with the frass of the powderpost beetle. The frass can have the consistency of talc or powder depending on the specific species of the beetle. The powderpost beetle prefers many hardwoods including oak, ash, hickory, and cherry to name a few. Piles of sawdust appear from small holes in logs that are infested by the beetles. Powderpost beetles are very small brown, black in color which make them hard to see. Most homeowners will see the piles of sawdust more often than the actual beetle.

From one MSU articles explains:

“These small beetles lay their eggs on or below the surface of unfinished wood. The young larvae that hatch burrow into the wood, creating small tunnels as they feed on the wood. Often the only sign of these beetles are numerous small pinhole openings in the wood and fine sawdust that accumulates in and around holes where larvae are feeding. Powderpost beetles that come into the home in firewood can move from the logs to other wood that is unfinished, such as frames inside of furniture as well as structural wood within the house.”

For more information on this beetle see the following Ohio State link: Powderpost beetle.

Storing this wood in your garage is usually not recommended, you certainly do not want any unwanted guests to travel or to introduce new problems. Before using or burning this wood you do want to make sure that it is properly cured. The following are general guidelines from Purdue

Bring firewood indoors only as needed, at most a couple of days supply at a time. Storing firewood in the home for long periods speeds insect development inside the wood, which allows them to emerge inside the home.

Do not stack wood up against the house or garage. This can result in moisture or insect problems in the building. A minimum of 3 feet between the firewood and building should be maintained. This also allows better air circulation, which promotes more rapid and thorough drying of the wood. Stacking the wood off the ground whenever possible also will increase drying and reduce potential pest problems.

I have include links to MSU articles that will provide you with more information on storing and curing firewood.

Use firewood wisely

Best way to store firewood

You may be bringing in more than just wood

I hope you find this information beneficial. Thank you for using our service.