Bugs in my Walnut?

[Brooks Kieffer]

I am working on a Walnut slab table top about 3" thick. I am probably about 98% completed. BLO on all sides, many coats of shellac followed by many coats of Waterlox. I just came down to my shop and niticed a small (1" dia.) mound of what feels like fine sand in the middle of the slab. Under it I can feel a small, pin head sized bump. Me thinks me has bugs. Anyone have any idea what they might be or better yet, how to get rid of them?
Thanks for the help!

[Frank Drew]

Brooks,

The dust, or frass, might be from powderpost beetles; can you see a small entry hole? They mostly attack sapwood but bugs will do what bugs will do and you can find damage anywhere.

[Brooks Kieffer]

If there is a hole it is very small. Seriously, about the size of a pin head.

[Frank Drew]

The hole a powderpost beetle makes is maybe 1/16" or so. I have a small chunk of very hard rosewood with several even tinier holes, made by whatever unknown critter; I'm amazed that a bug that could drill into that wood, as dense as it is.

[Chip Lindley]

Kiln drying kills these critters! But if your wood is air-dried, you are at their mercy. Heat is not an option now, since your tabletop is completed, BUT perhaps fumigating IS! The slab could be slipped into a plastic bag and gassed with something recommended by a reliable exterminator. Whole houses are done this way! So, a tabletop should not be such big deal!

[Corey Wilcox]

I can't tell you how to get rid of them if it is powder post beetles, but I can tell you that they are highly persistent. I just resawed a piece of spalted maple earlier this week that has been in my shop for no less than 7 years. It looked okay on the outside, but when I cut it open I found that the inside was pretty well destroyed with by beetle boring and upon closer inspection actually found two live, albeit resawed, worms wiggling around. So if you think you may powder post beetles show no mercy and give no quarter! Also might be good to check the rest of your stock if you had any nearby.

[Dave Tinley]

I have 7 boards, all Ash, they are 11-12 inches wide, and 9 feet long.
They have been sitting outside, stickered for two years now.
Four months ago i noticed the small pin holes and little mounds of dust.
After some research I found that they can be killed in a kiln, since I am not anywhere near a kiln I was told of another method. Wrap the boards in black plastic, like they sell in the paint dept. Leave it in the sun for a couple of weeks and that should do it.
I have not tried that yet, and dont know if that will help in your situation.
I did take one board, cut it in half and ripped down the middle. I used those to boards for new sawhorse tops. I coated both sides with marine varnish, very heavily. That was ten days ago, todate I have not seen any activity.
Could be the little buggers have full stomachs, or they could just be hiding out inside.


Dave

[Richard M. Wolfe]

Walnut and especially ash are favorites of powder post beetle. The only effective way to kill them is by heat. Fumigation won't work as the critter is inside the wood and can't be reached by insecticides. Wrapping the wood in black plastic and putting it in the sun is effective provided the wood reaches 130 degrees. What I've read recommends 130-150 degrees for at least four hours.

Within the past couple months I have found powder post beetle in both bois d'arc (osage orange) and pecan, and I've never seen them in either of those. Hope it's not a new species or adaptation.

[Frank Drew]

I had more damage to ash than to any other wood I've used; I don't mind so much getting holes in cherry or walnut sapwood since I'd cut those parts off anyway.

[Larry Edgerton]

Walnut and especially ash are favorites of powder post beetle. The only effective way to kill them is by heat. Fumigation won't work as the critter is inside the wood and can't be reached by insecticides. Wrapping the wood in black plastic and putting it in the sun is effective provided the wood reaches 130 degrees. What I've read recommends 130-150 degrees for at least four hours.

Within the past couple months I have found powder post beetle in both bois d'arc (osage orange) and pecan, and I've never seen them in either of those. Hope it's not a new species or adaptation.

Heat is not the only cure, but it is the reason that I do not allow any wood that is not kiln dried in my shop. I do not want them to get a hold on my wood stocks.

Anyway..... You can treat stacks of wood without heat. Mix a solution of 21 Mule Team Borax and water in a garden sprayer and mist your wood stocks. It will take care of the powder post beatles. This is a "Secret" formula used by exterminaters to get rid of them in a house. It does not hurt the wood that I have noticed, but I store all of my wood in the rough.

I anually clean my shop and mist my wood storage area with this solution as a precaution. I am not sure what you can do about your finished project, maybe burn it and treat the rest of the wood and your shop.

[george wilson]

That concentrated borax solution is what the millwork shop used near my old shop. That stuff is VERY expensive!! If you can make your own,do so.

Isn't there a real danger of getting those beetles everywhere in your house,as well as in your wood stockpile? I'd get that table away from valuable things until I could make sure they were all dead.

[Richard M. Wolfe]

For a borax treatment I use TimBor. As I recall a 25 lb bucket costs about $75. Mix it in a pump-up sprayer. It's only effective if applied immediately after wood is milled. The powder post beetle lays eggs on the treated wood and the grub ingests the treatment as it bores into the wood. Since the borax is only on the very top layer of wood the treatment, like fumigation, is not effective for wood which already has the larvae down in the wood.

Heat treating is about the only sure fire method of eliminating powder post Once the wood has dried to a certain point large borers (the ones that make a hole about a quarter inch across) won't get in it, but powder post infect fairly dry wood....wood with moisture to about 10-12%. So now the kicker . Just because wood has been kiln dried (and yes, kiln dried properly) doesn't mean it won't be attacked by powder post. I got a small batch of red oak that I know had been kiln dried and I didn't use it for a while; it was stored in a non-conditioned storage area. Several months later when I went to get some I found a number of boards riddled with powder post. In some cases the kiln dried wood "acclimates' back to a moisture content that the powder post can tolerate. I find that I don't have that much of a problem with most woods that have been dried, though. The beetle larvae is going after starches and sugars which are mainly in the sapwood and very top of the heartwood and so can usually be cut out. Prolonged storage seems to alter 'something' and make it less of a target. But it depends on the wood. The prime target for powder post that I have is mesquite. I have had them riddle sapwood in 'fresh' mesquite so badly I could grab a handful of sapwood and break it loose from the board and powder it in my hand. That's why about all mesquite pieces you see have the sapwood removed. If a piece is made and sealed properly it should keep them out, but the majority of the people don't take a chance - if there's the slightest opening they find it. But after some extended storage time the yellow mesquite sapwood ages to an off white. It's still susceptible to powder post but not nearly as bad. On the other hand, I have had ash that was several years old that the critters continued to use as a buffet. I have heard of furniture being attacked by powder post, but a combination of sealing with a finish and age make this fairly uncommon. I can't remember offhand what the critter is that gets into furniture in Europe (I've seen numerous references to English furniture) but I'm glad we don't have it here.

[Frank Drew]

Just because wood has been kiln dried (and yes, kiln dried properly) doesn't mean it won't be attacked by powder post.

That's been my experience, too, Richard, with kiln-dried ash. I liked, and maybe even prefered, air-dried walnut and cherry, but I wouldn't bring any affected wood into the shop until I'd trimmed off the affected portions.

[David G Baker]

A friend of mine is renting a farm house that has 4 or 5 out buildings that are infested with powder post beetles. He has told the property owner several times about the problem but the owner ignores him. The problem is so bad that there are piles of powder surrounding the main support beams in the barn.
I am not sure what type of wood the house flooring is made from, several times while visiting he would point out the tiny holes in the floor so they have invaded the house as well.