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I found bugs in wood that I've had air drying for the last few years. What are they, and is the wood still safe to use?

I had a tree cut down a few years ago and some of the wood milled in to slabs. It's now time for me to start using it and so far I've come across some very nice pieces. However, I've also found a piece that appears to have bugs living in it. They seem to be some kind of larva.

I could carefully examine every piece I use, but that won't catch them all. In this case, these were uncovered after a few passes through the planer. While the end plan for this particular piece involves being covered in a layer of epoxy, that won't be the plan for every piece in the pile.

Closeup of bugs found

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  • Well it's some kind of wood-boring insect of course, but an attempt at specifics would need your location. Where in the world are you? "is the wood still safe to use?" Sort of. Structurally, if the wood is not badly undermined (as can happen with long-term infestation) then it's fine as long as you kill ALL of the bugs (at every stage in the life cycle) This is, regrettably, harder to do with 100% assurance than one might think, unless you have access to an industrial freezer. This board and all the other slabs (which you must assume are also infested) are a big problem [contd]
    – Graphus
    Dec 4, 2021 at 19:26
  • ...and should be removed immediately if they are indoors Like, right now. It's not just this wood, potentially you have to worry about your workbench(es), wooden tools handles and even the studs in the walls!
    – Graphus
    Dec 4, 2021 at 19:30
  • Location is Central US (Missouri).
    – Elros
    Dec 4, 2021 at 21:47
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    @Elros. You should check with your local agricultural agency before disposing of the wood. It can easily infect other trees if not properly handled and your community/state may have specific protocols.
    – Ashlar
    Dec 5, 2021 at 2:54
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    Someone at Biology or The Great Outdoors might be able to ID the little suckers.
    – FreeMan
    Dec 6, 2021 at 19:20

2 Answers 2

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The easiest way to guarantee you will kill them all is to have the boards kiln dried. Safe is relative, they are very unlikely to be dangerous to people. I also don't think they are much of a real problem for homes or other wood based things. Many of these larva are fairly species specific. Also outside of termites, I've not heard of to many bugs eating up houses or furniture at least none that wasn't already water damaged.

Having said that, they will continue to eat your lumber until they die or pupate and fly away, so kiln drying is the way to go (even a solar kiln). Many wood borers die just from the lumber drying naturally, it doesn't have enough moisture for them to survive. So these are a little hardier. The best bet for identifying them though would be to talk to local foresters, National Forest Service, DNR or some other similar place. If they are actual pests that need watching they'd like to know, or they just might be a normal 'tree disposer' that is 'relatively' harmless.

I've milled a lot of wood, every now and then I've found them with worms eating them. Never had any long term issues with an 'infestation'.

The Emerald Ash Borer actually needs living trees to eat. They live under the bark and will bore a little ways into the sap wood. Peeling the bark off is the 'sure-fire' way not to transport the EAB.

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  • Obviously kiln drying will do it, but I would debate the "easiest" here on a number of grounds. Firstly, finding a kilning operation within easy reach might not be that simple. Secondly, and possibly the most important, they might be reluctant to handle the wood (similar to how many mills won't slab urban trees).
    – Graphus
    Dec 6, 2021 at 20:32
  • @Graphus, I'll give you that I didn't think about 'ease' of finding a kiln. I think you can find a kiln with in 2 hours of most cities and towns around here. But at least in MN WI none seem to worry too much about pest in the kiln since it kills them. But you are right that doesn't mean someone might not have a problem with them. Still what would be easier? Chemical treatments? Not high on my list of things. Could always build their own solar kiln I suppose.
    – bowlturner
    Dec 6, 2021 at 20:41
  • Freezing is a possibility (and as I was just saying in another Comment it has the advantage that it doesn't alter the wood). But finding a commercial operation with a suitable freezer isn't straightforward for a lot of people. A home freezer might work if A, it goes down low enough and B, the pieces aren't too large, which of course they could easily be. Because the wood is permanently marred with what most consider to be very unsightly channels there's a lot to be said for just cutting one's losses and dumping it, or using it as firewood (this is what many do here if woodworm is found).
    – Graphus
    Dec 6, 2021 at 20:52
  • @Graphus true on the burning as an option. But Freezing won't always work. Maybe in MO, but up here in the northland a lot of our bugs just hibernate.
    – bowlturner
    Dec 6, 2021 at 21:07
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    Freezing always works IF you can go cold enough. This is why industrial freezers are to be preferred for this, if possible. Home freezing can work too even though the temps aren't typically nearly as low, if you can freeze fast enough to circumvent the natural winter response of the non-adult phases. This is one of what I believe are the two main methods now employed both by enthusiasts and professional restorers to deal with what we call simply woodworm (common furniture beetle) and other wood-boring insects elsewhere in the world, if found on whole pieces of furniture, radio cabinets etc. .
    – Graphus
    Dec 7, 2021 at 15:07
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I'd imagine that canned air (commonly used for blowing the dust out of electronics) would do the trick for spot treating the wood with a freeze treatment. When held upside down, the air comes out cold enough to cause frostbite in seconds.

Canned air:

Can of air
First image found in a web search for "canned air". Courtesy of Amazon.com. Click to embiggen

Spend an hour or so in the shop or in the backyard sunshine, enjoying your beverage of choice. Keep the board in front of you and the can of air close by (do not confuse the canned air for your beverage - author not responsible for frostbitten tongues).

Every time you see one of the little buggers sticking his head out, grab the can, turn it upside down, point the straw at him and give him a spray. Even for northern bugs that hibernate over the winter, this treatment should freeze him right to death. Shake the board until his little, frozen corpse falls to the ground. If you're outside, let him be recycled into fertilizer. If you're inside, clean up according to your local shop cleanliness standards.

Alternatively, be more aggressive and simply spray into each and every tunnel.

You'll have to keep an eye on the wood for a while to ensure you got them all, whether you go for the slow, relaxing approach or the quick aggressive one.

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    Uh, as satisfying as I'm sure this would be it just won't work to rid the wood of the bugs. These channels were exposed by planing, but any channel elsewhere in the wood with a live larva still resident in it almost by definition doesn't have an exit hole or any other intersection with the surface.
    – Graphus
    Dec 8, 2021 at 0:09
  • oh, yeah. valid point. But it would be fun! ;)
    – FreeMan
    Dec 8, 2021 at 0:33

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