I have a couple of rough-sawn (4-inch x 22-inch x 8-feet) black walnut planks that have been kept in unheated storage for the past 30 years in Southern Minnesota. When I began planing them, I found little white grub-type creatures about the diameter of pencil lead and about 3-4mm long. I don’t really care what they are, but how do I get rid of them?
Simon Watts: I think you would be most unwise to make furniture out of the walnut you describe — unless you want to make a feature as was done with ‘Wormy Chestnut’ years ago. My guess is that only the sapwood — nearest the bark — is infested and you could cut it off and use only the heartwood.
Lee Grindinger: You have a couple of options. Exposing the lumber to 140 degree heat for 24 hours will rid your lumber of these beasts but this requires close attention to humidity during the process. The easiest way to rid yourself of these insects is to remove all the sapwood from your lumber. Bugs rarely bother the heartwood of walnut. Another option is to treat the lumber with an insecticide such as Boracare. These chemicals are applied with a brush or sprayer. Bug bombs under tents are another option but this is only marginally effective since it won’t kill the eggs. I’d highly recommend identifying these grubs. A county agent can do this and if they turn out to be powder post beetles you should closely monitor your lumber and furniture. There are several borers and knowing which one you have is important.
Michael Dresdner: Most major pest control companies can direct you to a local firm that does contained fumigation. That means the wood will go to their site, be fumigated to kill the darling worms, and returned to you clean as a whistle. By the way, have you checked all the other wood that this was stored near for infestation? That includes the wooden structure it was stored in.
