Bug Holes in Air-Dried Maple

Advice on a lumber insect infestation. March 4, 2009

A while back I bought a bunch of hard maple from a local sawmill because it was cut it for an order that had fallen through. Well I got a good deal on the maple so I bought it and have dried about half of it. I put the wood up on sticks as soon as I got it and then put the stacks in a shady area and covered the stacks.

All was good until the other day I noticed that after I had planed some of the boards for a customer that the entire length of the board was dotted with small pin holes about the size of bird shot. In fact it looked like the boards had been shot with a shotgun. The lumber had been sawn on a circular mill and with the rough surface the small holes are not very noticeable until the wood is planed.

My question/dilemma is - were the boards sold to me this way and are therefore the sawmiller’s fault? Could the stacks of maple been attacked by some kind of bug while drying or after kiln drying?

To me the holes look like powder post beetles but I don't know if they attack maple or not. I kind of doubt that they would go after kiln dried wood that was stored in the shop. Not all the boards have holes but I've found enough that this is a major problem. I would appreciate it if anyone had any info on how these small holes got there and if it was most likely in the logs or problem came during drying process.

Forum Responses
(Sawing and Drying Forum)
From Gene Wengert, forum technical advisor:
It is impossible to diagnose and identify this insect by e-mail. There are two main possibilities - ambrosia beetle and powderpost beetle. The first prefers wetter wood and is commonly found in air drying, especially slow air drying. The second is not so common and is usually a result of exposure to other wood that is infected and is only is drier wood. In either case, it is not the sawmiller's problem.

From contributor S:
If you still have any of the boards that have been stacked for a while, carefully look at the stacks and see if you can detect any sawdust on the boards in little piles. This would indicate that the bugs are still in there chewing away. It’s pretty hard to determine when they got in there. The best you can do is make something rustic out of the wormy maple. But you need to get it kiln dried to make sure the bugs are dead. Now you know what to look for when you buy lumber.

From the original questioner:
I think it sure could be the miller’s fault if he was sawing wormy logs. All the lumber was graded by a professional grader but the holes are so small that they are very hard to see. I didn’t notice them until the boards were surfaced. Maybe the holes happened during the air drying process. There’s probably no way to know for sure.

From Gene Wengert, forum technical advisor:
These very small holes would not normally occur in a log unless the log was badly mishandled, and if mishandled, there would be other evidence. If they were in the log, it would have to be an old log that was not promptly sawn and there would be blue stain and even white rot as well. Further, if you put two adjacent lumber pieces together, the holes would line up if it happened in the log. If the log were recently harvested from a live tree and sawn within a month, there would not be a risk for such insects getting into the log.

The slow drying mentioned gives strong evidence that they are ambrosia beetles that thrive in such drying conditions. Oftentimes we can see these insect holes in the stickers as well. Did you look at the stickers?

From the original questioner:
I will look at the stickers to see if I can find any holes in them as well. Most likely the cause was my slow drying. I put some in the kiln right away but got an order to custom dry a bunch of lumber and couldn’t get the rest of the maple in for a long time. Some is still on sticks. Is there any chance that the bugs could spread to other lumber stored near the maple? Do you think I can put this back into kiln and just sterilize it by letting it sit for a few days with temps above 145 degrees?

From Gene Wengert, forum technical advisor:
If they are still active in KD lumber, then they can spread. If active in air drying, they can spread to other air drying lumber. Clean the area of all wood debris to prevent this. Insecticides will not be very effective however. A county extension agent may have more info.