Bugs in Dried Walnut Lumber

[locustoak]

I dried a batch of black walnut in my solar kiln this year, and now am having a bug problem! The batch of walnut I dried earlier in the year turned out fine. However, the last batch that sat outside air drying until mid/late summer ended up getting bugs. Does anyone know what these are or how to get rid of them? 
They are mostly eating the sapwood, and are still active after 3 months out of the kiln. Wood was dried to 6-8% moisture, which I thought would have deterred any feeding insects.

I still haven't found any larvae, or the bugs themselves, just the powder. Nor are they spreading to any other lumber, even non-affected walnut stacked next to them. Rather just staying inside the infected boards. Would anyone have any guesses as to what they are or how to get rid of them?

[YellowHammer]

That's exactly why I don't sell wood directly from a solar kiln without sterilizing in a DH kiln, and what you are seeing is not abnormal for a solar kiln, but certainly undesirable.

Need to see the holes with no frass to better identify the insect, but it really doesn't matter, they are there and active.   

Walnut sapwood is generally where the insects attack first, especially if the logs were not sawn fresh, or sat for a little while.  It's just one more reason I will strip the sapwood off in walnut lumber.  It's often a "carrier" of joy, and the easiest way to get rid of the bugs in sapwood is to get rid of the wood they are infesting.  So whack off the sapwood for a good start.  

  It's a common myth that bugs won't attack dry wood, especially in the lumber world, but of course, people wouldn't pay for a termite or bug guy to routinely spray their house with most of the wood at 7% unless it wasn't a potential problem.

Anyway, if the bugs are coming out, which is most likely, after living as a larvae in the wood, the momma usually drops big load of eggs right in her tunnels as a going away present.  Merry Christmas.

The easiest and most sure way is to simply put the wood back in the solar kiln, let it heat up as much as possible and hit a sterilization temperature in the core of the wood of 133F so most people run it up to 140 of I use 150F and maintain for 24 hours, I used to use about 2,000 watts of halogens lights in my old solar kiln as extra heat.  Everything in the wood will be dead, and end of problem.  Don't go overboard, depending on the clear glazing, you can burn or blacken it. 

You can spray it, but that is more of a surface treatment.  Bugs happen, it's Nature, you'll just have to deal with it.       

[locustoak]

Here is a picture of the holes. Nice oval shape.

[YellowHammer]

Sure looks like powder post beetles to me.  Bullet round holes, clear sides, like made with a drill bit, in dry wood.  Lots of info on the Google about them.  I consider any wood containing an active infestation no different than a hunk of radioactive lumber being pulled from the basement at Chernobyl.

They make the holes as they leave the lumber as full gown beetles about 1/16" in diameter, and have a lava life cycle of up to 3 years in the wood.  I bet we get about a call a week from a desperate non customer who bought wood from someone else and now their house, flooring, furniture, lumber stack, slab, table, overhead beams, headboard, kitchen counter, (just pick one) etc is crawling, and what can they do about it?  Depending on the damage or situation, I give them about three alternatives after I warn them that they need to act quickly, because they spread: 1.  Call the guy where they bought the lumber and get their money back (they never get a refund), 2. Call their insurance company, 3.  Call their lawyer, and 4. NO, I will not sterilize and fix the lumber they bought from my competitor and no, I don't want that radioactive disaster here, anyway, to potentially infect my wood.

Anyway, you have a kiln and a sawmill, and have everything you need to take care of the issue, but you will have to be able to maintain a 140F minimum in your kiln (there was a pretty good thread about it here on the Forum, recently).  Bugs in wood happens, it's wood and it's Nature.   Just don't let them spread to your other wood, and I wouldn't recommend selling it to anyone.  Old Yellowhammism "Bugs is bugs, and bugs is bad."       

[scsmith42]

You can augment heat into your solar kiln in several different ways.  Robert mentioned using halogen lamps; in my instance I plumbed in an LP space heater for sterilization purposes.  Works well.

[locustoak]

Out of curiousity I took some of the bark off, and found a few of these grubs under the bark. They look like what is causing the holes in the wood. Has a fat head. Also, to clarify, the holes are oval shaped and not round. It doesn't seem to be affecting other wood, just what was in that batch.

[doc henderson]

@locustoak , do they taste salty or have a more buttery flavor...?


just kidding, but i have seen some like that before, but I cannot ID them for you. 

[Magicman]

That Longhorn Beetle grub as nothing to do with the 1/16" holes pictured above.

Those holes could be caused by Ambrosia Beetles which are exiting as the lumber dries.  If so, they are "leaving town" and will cause you no further grief.

[YellowHammer]

It is normal for old logs with sapwood to have a variety of bugs in them, the sapwood contains the energy of the tree, rots first, and is the food.

Ambrosia beetles look like real beetles, only very small, and have a bulb on the tip of their antenna, like a cartoon character.  Normally, you have to take a photo with your cell phone to see the bulb, but it will be there.  Ambrosia beetle larvae feed on a black fungus called "ambrosia" in the moist wood, and if you saw into the wood, you will find a very characteristic black lined horizontal gallery where the babies lived and fed, before they grew into beetles. 

On the other hand, powder post beetles look like a very small piece of pencil lead, long and cylindrical, and they leave a non fungus stained hole, as they eat the wood.  They always leave frass.  Putting wood in a solar kiln, with enough heat to dry wood, but not enough to kill them, basically supercharges everything in the wood, everything wants to leave, and nothing dies.  I had a solar kiln, and it was frustrating.

As I mentioned, the life cycle of a PPB is years, you will not see a speading infestation.  That is the problem.  They lay eggs on uninfected wood as they leave, the larvae are almost too small to see, hatch and bore into the wood and you will not know it.  Years later, they will emerge as beetles.  Powder Post Beetles do exactly as their name implies, turn wood into powder. 

You may easily have both species, and more, in the same pieces of rotting sapwood, plus a bunch of others. However, as a rule, if I see a round bullet hole with no black lining, then, I always assume PPB's are the culprit and react accordingly.  Very good info and pics in the links below.

FYI, if a house gets infected with PPB's, the only certified treatment to kill them, at least in Alabama, is full house tenting and fumigation, and it starts at $25,000 bucks, not to mention the cost of the the repairs to the damage. By that time, it is an insurance claim, and the first thing they ask is "where did you buy the wood?" and they come after the company that sold it.     

https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5349704.pdf

https://entomology.ca.uky.edu/ef616